Earth Section - Scripps Institution of Oceanography

Earth Section 

scripps institution of oceanography, university of california, san diego

Earth Section Annual Report 

The Earth Section of the Scripps Institution of 

Oceanography comprises the Geosciences 

Research Division (GRD) and the Cecil H. and 

Ida M. Green Institute of Geophysics and 

Planetary Physics (IGPP). This report provides a 

snapshot of the research being conducted by 

investigators in the Earth Section over approximately 

the last academic year, with the goal of 

presenting a reasonably accessible description of 

our activities to scientifically literate but nonexpert 

readers. 

Our work spans a broad range of subject matter 

in geology, geophysics, chemistry, biogeosciences, 

and climate science. Observations, measurements, 

and collection of samples and data are 

accomplished on global, regional, and local scales 

by extensive shipboard and ground-based operations 

and also include remote sensing by satellites 

and the use of wide-ranging instrument networks. 

Extensive laboratory work often follows 

our sampling programs, while theoretical developments 

and modeling play a strong role in data 

interpretation and guide the design and implementation 

of experimental work. 

This report was compiled, edited, and produced 

by IGPP Deputy Director, Robert Parker, and by 

GRD Division Director and Earth Section 

Deputy, Jeffrey Gee, using material contributed 

by our individual investigators. It is our hope 

that you will find this a useful description of our 

ongoing work. 

Catherine G. Constable 

Director, Cecil and Ida Green Institute of Geophysics 

and Planetary Physics 

Head, Earth Section 

Scripps Institution of Oceanography University of 

California at San Diego 

9500 Gilman Dr., La Jolla, CA 92093-0225, USA 

Image: The icebreaker R/V Nathaniel B. Palmer approaching 

Terra Nova Bay in the western Ross Sea during a recent 

cruise led by researchers at Scripps and CalTech. 

Photo by Roi Granot.

Duncan Agnew, Professor and Frank K. 

Wyatt, Research Scientist 

Lihini Aluwihare, Associate Professor 

Laurence Armi, Professor* 

Gustaf Arrhenius, Research Professor † 

Luciana Astiz, Specialist* 

Jeffrey Babcock, Associate Project 

Scientist* 

George Backus, Professor Emeritus * 

Jeffrey Bada, Professor* 

Katherine Barbeau, Associate Professor 

Jonathan Berger, Research Scientist 

RTAD † 

Wolfgang Berger, Research Professor † 

Donna Blackman, Research Scientist 

Yehuda Bock, Research Scientist 

Kevin Brown, Professor* 

Steven Cande, Professor 

Paterno Castillo, Professor 

C. David Chadwell, Associate Research 

Scientist* 

Christopher Charles, Professor 

Catherine Constable, Professor 

Steven Constable, Professor in Residence 

Joseph Curray, Professor Emeritus* 

J. Peter Davis, Specialist 

Catherine deGroot-Hedlin, Associate 

Project Scientist 

Leroy Dorman, Professor 

Neal Driscoll, Professor 

Matthew Dzieciuch, Project Scientist 

Peng Fang, Specialist* 

Yuri Fialko, Associate Professor 

Robert Fisher, Research Scientist 

Emeritus* 

Helen Fricker, Associate Professor 

Edward Frieman, Professor Emeritus* 

Jeffrey Gee, Professor in Residence 

Freeman Gilbert, Professor Emeritus* 

Peter Guenther, Specialist RTAD † * 

Alistair Harding, Research Scientist 

James Hawkins, Research Professor † 

Michael Hedlin, Research Scientist 

David Hilton, Professor 

Glenn Ierley, Professor 

Miriam Kastner, Professor 

Graham Kent, Research Scientist 

Kerry Key, Assistant Research Scientist* 

Deborah Kilb, Associate Project Scientist 

Devendra Lal, Professor 

M. Gabriele Laske, Associate Research 

Scientist 

Yuguo Li, Assistant Project Scientist* 

Peter Lonsdale, Professor* 

Guenter Lugmair, Research Scientist 

RTAD † and Alex Shukolyukov, 


Todd Martz, Assistant Professor 

T. Guy Masters, Professor 

Stephen Miller, Specialist 

Jean-Bernard Minster, Professor 

Jens Mühle, Assistant Project Scientist* 

Walter Munk, Research Professor † 

Richard Norris, Professor 

John Orcutt, Professor 

Robert Parker, Research Professor † 

Stephen Piper, Specialist* 

David Sandwell, Professor 

Annika Sanfilippo, Specialist RTAD † 

Glenn Sasagawa, Associate Project 

Scientist 

John Sclater, Professor* 

Peter Shearer, Professor 

Hubert Staudigel, Research Scientist 

Lisa Tauxe, Professor 

Michael Tryon, Assistant Project Scientist 

Frank Vernon, Research Scientist 

Martin Wahlen, Professor 

Bradley Werner, Professor 

Edward Winterer, Research Professor † * 

Peter Worcester, Research Scientist 

Mark Zumberge, Research Scientist 

* no annual report available 

† Research Professor and RTAD = retired with active research program

Duncan Carr Agnew Frank K. Wyatt 

Professor of Geophysics Principal Development Engineer 

Email: dagnew@ucsd.edu Email: fwyatt@ucsd.edu 

Phone: x42590 Phone: x42411 

Research Interests: Crustal deformation measurement and interpretation, Earth tides, Southern 

California earthquakes. 

Crustal Deformation (Strainmeters) 

As was true last year, amajor activity this year has been constructing and operating longbase 

laser strainmeters as part of the Plate Boundary Observatory, anactivity led by Wyatt, supported 

by staff members Don Elliott and Stephen Dockter. This year, the construction activity has 

been just south of Cholame, in central California, where we have built two instruments at a location 

where deep tremor has been detected. These instruments began producing data in late 

August of 2008, so we can now say that we have met the PBO construction goals on time and 

within budget. We hav e also continued to operate the PBO instruments at Salton City (SCS), the 

PBO and USGS instruments at Durmid Hill (DHL), and the strainmeters at Piñon Flat Observatory 

(PFO), and Glendale (GVS). 

One particularly interesting result for the last year came from the instruments at Durmid 

Hill, which recorded a long sequence of aseismic strain events at the southern end of the southern 

San Andreas fault beginning in April 2008. The Coachella segment of the San Andreas, on which 

these events happened, has an 8-m slip deficit, and its southernmost end, where these strain 

changes are seen, is a possible initiation point for a future great earthquake. 

Figure 1shows the last 2.4 years of data from some of these sensors (to the end of May 

2008). The top panel shows the long-term records from the two laser strainmeters. The longterm 

rate on the NS instrument is −0.31 µε/yr; the newer EW system shows a rate of 0.49 µε/yr 

(both instruments are actually 5° counterclockwise to the directions given, to be at 45° to the local 

fault strike). These rates are consistent with the shear expected from a dislocation model, though 

there combination implies local dilatation that is not so easily explained. The second panel shows 

data from the University of Colorado creepmeters (operated by Dr. Roger Bilham) that are located 

across the fault about 2 and 9 km NW of its closest approach to the strainmeters. Both creepmeters 

show ongoing cross-fault slip at rates of 1-2 mm/yr, with some left-lateral motion at times of 

heavy rains. Both creepmeters also show anabrupt signal beginning on 2008:104, which was 

also very clear on the strainmeters. The third and fourth panels from the top of Figure 1show 

nearby GPS baseline changes, one between DHLG (the GPS station at DHL) and station P505, 

which is on the other side of the San Andreas. P505 moves only 6 mm/yr in a North-America reference 

frame; relative to it, DHLG moves 8.2 mm/yr fault-parallel and -0.8 mm/yr fault-normal, 

with no obvious fluctuations. The other GPS line shown is from from P505 to P504; this line is 

entirely on the east side of the San Andreas, and shows a possible transient beginning sometime 

in the summer of 2007, though this is combined with a possible annual cycle. 

On another creeping section of the San Andreas fault between Parkfield and Hollister, ithas 

been known for some time that creep at the surface often occurs in ‘‘events’’ with relatively rapid 

slip. The recent changes seen at DHL also seem to occur mostly as events, which the strainmeter 

data allow ustoresolve ingreat detail, both in strain (1% or better of the total) and in time (1 Hz 

sampling). The individual events are not simple or repeatable; instead they show arange of 

waveforms. This is actually useful, since this variety allows us to explore the spatial and temporal 

behavior of creep events on the fault. In particular, the ratio of strain change on two instruments 

from one sample to the next restricts, as a function of time, where strain can occur; the 

challenge is to combine this with other data to produce a plausible history of aseismic slip.

Publications 

-2- 

Figure 1 

Agnew, D.C.(2007) Earth Tides, pp. 163-195, Tr eatise on Geophysics: Geodesy, T.A.Herring, 

ed., Elsevier, New York. 

Rolandone, F., R. Burgmann, D. C. Agnew, I.A.Johanson, D. C. Templeton, M. A. d’Alessio, S. 

J. Titus, C. DeMets, and B. Tikoff (2008) Aseismic slip and fault-normal strain along the 

central creeping section of the San Andreas fault, Geophys. Res. Lett. 35, L14305, 

doi:10.1029/2008GL034437. 

Agnew, D. C.(2008) Benioff, Victor Hugo, Complete Dictionary of Scientific Biography 19 

243-245 (Charles Scribner’s Sons); Menard, Henry William, ibid 23, 96-97; Richter, 

Charles Francis, ibid 24 241-243.

Lihini I. Aluwihare, Associate Professor of Marine Biogeochemistry 

laluwihare@ucsd.edu, 2-4886. 

Research Interests: Carbon (C) and Nitrogen (N) Cycles of the upper ocean, isotopes ( 14 C and 15 N) and 

chemical composition as tracers of the biological and chemical history of organic matter in marine 

environments, microbial C and N metabolism in the deep ocean, identifying novel biomarkers for studies 

of microbial ecology and/or organic matter cycling. 

The extent of the balance between photosynthetic carbon production and respiration determines 

the strength of the biological carbon pump in marine environments. A significant fraction of the 

respiration (estimates range from 30-80%) is mediated by heterotrophic bacteria, which interact primarily 

with dissolved organic compounds. These dissolved compounds represent the ocean’s largest (670 Pg C) 

and oldest (~ 6000 years) reduced carbon reservoir and their accumulation identifies a short circuit in the 

balance between photosynthesis and respiration. As such, the chemical and biological characteristics of 

this large dissolved organic carbon (DOC) reservoir are of particular interest to carbon cycle research. 

Figure 1 (de Jesus et al.). A. The chemical fractionation scheme for DOC. 1 H NMR spectra highlight major 

functional groups in each fraction. Δ 14 C values are given in blue (more negative numbers show older material and 

more positive numbers identify younger carbon). B. The cycling of labile and refractory DOC as deduced from both 

the isolation scheme and Δ 14 C data presented in A. Multiple arrows identify processes that occur on long timescales. 

The refractory lipid in marine environments is shown here to be associated with labile carbohydrates through an 

ester bond that may be hydrolyzed during transit through the water column. 

Recently our research has focused on identifying the composition of dissolved compounds that 

accumulate in the ocean on millennial timescales and delineating mechanisms that might lead to the 

accumulation of organic carbon in the ocean. Our recent work in the eastern North Pacific Ocean 

identified structural features that facilitate DOC preservation in marine environments by showing that 

compounds accumulating on long timescales were dominated by aliphatic functional groups (e.g., lipids) 

while polar biochemicals such as carbohydrates accumulated on only short timescales (Figure 1 A). The 

design of our analytical scheme also enabled us to demonstrate intermolecular interactions that contribute 

to the transient accumulation of bioavailable compounds in the upper ocean (Figure 1 B).

Part of our work on the marine carbon cycle has led to an investigation of carbon sources utilized 

by microorganisms (bacteria and archaea) in the deep ocean. Carbon flow through the microbial 

community at two depths in the mesopelagic zone of the North Pacific Subtropical Gyre was examined by 

exploiting the unique radiocarbon signatures (Δ 14 C) of the three major carbon sources in this 

environment. The radiocarbon content of nucleic acids, a biomarker for active cells, isolated from sizefractionated 

particles (0.2-0.5 µm and > 0.5 µm) showed the direct incorporation of carbon delivered by 

rapidly sinking particles into the community at 915 m (Figure 2A). However, at the two depths examined 

(670 m and 915 m), autotrophic carbon fixation also appeared to support a significant fraction - 36% (915 

m) to 100% (670 m) - of the free-living microbial community (0.2-0.5 µm size fraction) (Figure 2A). The 

latter finding is supported by quantitative PCR results, which show greater abundances of genes encoding 

for Crenarchaeota and archaeal ammonium monoxygenase (amoA), a gene involved in archaeal 

chemoautotrophy. Results further showed that utilization of the ocean’s largest reduced carbon reservoir, 

14 C-depeleted DOC, was negligible in this environment. This study demonstrated that photosynthetic 

carbon is not always the major carbon source supporting microbial production in the deep ocean and 

recognized significant spatial variability in carbon sources supporting microbial production in this 

environment. 

Figure 2 (Hansman et al.) A. ∆ 14 C values for 0.2-0.5 µm (squares) and > 0.5 µm (triangles) size fractions of 

DNA extracted from 21 m, 670 m, and 915 m, along with vertical profiles of ∆ 14 C-DOC and -DIC. The shift in 

∆ 14 C-DNA once corrected for possible contamination from DOC adsorption, is shown by arrows originating at each 

measured point and traveling in the direction of more modern ∆ 14 C values. Also included are archaeal lipid ∆ 14 C 

data from 21 m and 670m (diamonds; Ingalls et al., 2006). B. qPCR data for 0.2-0.5 µm size fraction DNA samples 

showing relative abundances of bacterial 16S rRNA, group I Crenarchaeota 16S rRNA, and archaeal amoA gene 

copies per ng total DNA. The latter genes are related to the abundance of chemoautotrophic archaea. qPCR data are 

normalized to the 670 m 0.2-0.5 µm sample. 

References Cited: 

de Jesus RP, Aluwihare LI. “Relationship between chemical composition and reactivity in DOM.” In review. 

Hansman RL, Griffin S, Watson J, Druffel ERM., Ingalls AE, Pearson A, Aluwihare LI. “The radiocarbon signature 

of marine organisms in the mesopelagic ocean.” Submitted. 

Ingalls AE, Shah SR, Hansman RL, Aluwihare LI, Santos GM, Druffel ERM, Pearson A (2006) Quantifying 

archaeal community autotrophy in the mesopelagic ocean using natural radiocarbon. Proc Natl Acad Sci USA 

103:6442-6447.

Gustaf Arrhenius 

Research Professor of Biogeochemistry 

Email address: arrhenius@ucsd.edu 

Phone extension: 42961 

Research Interests: Spontaneous synthesis of RNA type molecules under simulated primordial 

atmospheric/hydrospheric conditions. Search for traces of earliest life in Earth's oldest 

sedimentary rocks. 

Collaborators: Prof. Chiara Daraio and Dr. Abha Misra, Aeronautics & Applied Physics, 

Calif. Inst. Technology; Prof. Lea Rudee, Computer & Electrical Engineering Science, UCSD; 

Saul Perez Montano, SIO. 

A major aim of our Exobiology work continues to be an exploration of the different 

forms at a molecular level that carbon, contained in Earth's oldest rocks, takes under the 

influence of time, heat and pressure. The ultimate aim is to follow these transformations and 

preservation back in time into the oldest known metasedimentary rocks (3.8 billion years) and 

use them for identification of organically derived carbon (meteoritic or biogenic). The results 

so far indicate the presence of carbon of organogenic - biogenic origin back to 3.8 Ga with 

isotopic indications that it came from primitive organisms that already had a history of basic 

metabolic evolution behind them (enzymatically mediated carbon fixation). Hence life 

probably arose earlier, likely much earlier, perhaps when bodies of liquid water first formed on 

the planet. John Valley and Simon Wilde at U. of Wisconsin and others recently found 

indications of water in remnant crystals from rocks up to 4.3 billion years old. 

A recent development in this search, which is as much of a materials science interest 

and rather dramatic, is the first discovery of carbon nanotubes in nature as transformation 

products of seemingly organogenic carbon in some of these rocks - examples are shown in the 

figures below. This discovery was made by our Co-I, Prof. Chiara Daraio, Visiting Research 

Scientist at SIO and her postdoc, Dr. Abha Misra. Prof. Daraio recently made another related 

discovery of great potential technological importance - that properly configured carbon 

nanotubes can be designed as active elements in electronic circuits - for this discovery she was 

earlier this year awarded the International Richard von Mises Prize in Applied Mathematics 

and Mechanics. 

High resolution transmission electron microscopy is a powerful method for revealing 

disordered carbon in the form of curly and concentric graphene microdomains which resist 

complete ordering up to a metamorphic range of 500-600 C and 5 -5.5 kb in rocks as old as 

3.8 Ga.

5 nm 

. 

Fig.1 The ORGANIC (meteoritic or biogenic) VS. INORGANIC source of carbon is revealed 

by its molecular structure 

- fluid deposited carbon crystallizes as regular graphite (left) 

- organically (in this case biogenically) derived carbon evolves as highly disordered puckered and 

curly structures (right) 

100 nm 

The tubes are produced by metamorphism 

of disordered carbon, catalyzed by 

transition metal crystallites like magnetite 

5 nm 

25 nm 

Fig. 2 Nanotubes growing from disordered organogenic carbon 

Fig. 3. 

Satellite image 

of southern 

Greenland. 

Red ellipse 

encloses the 

Isua 

Supracrustal 

Belt with 

metasediments 

3,780 million 

years old, 

partly covered 

by the inland 

ice 

Fig.4. Alternating graded layers of 

metavolcanic sediment and carbon rich 

shale, Isua Supracrustal Belt, southern 

West Greenland, hosting the putative 

oldest traces of life on Earth.

Kathy Barbeau 

Associate Professor, Marine Chemistry 

Email address: kbarbeau@ucsd.edu 


Research Interests: biogeochemical cycling of trace metals in the marine environment 

Research in my laboratory is directed towards understanding how biologically active trace 

metals cycle through the upper ocean, and how these cycles influence (and are in turn influenced 

by) organisms that live in planktonic communities. I use an interdisciplinary combination of 

techniques in my research, including chemical analyses of trace metals in seawater, experimental 

studies of metal uptake and transformation, and incubation studies to assess the response of 

biological communities to metal limitation. The biogeochemical cycling of iron is a particular focus 

of my research. Major field research activities in 2007/2008 included several cruises to examine 

the ecological significance of iron as a limiting or co-limiting micronutrient for phytoplankton, in 

different oceanic regimes. I also maintain an active laboratory-based program of mechanistic 

experimentation to study questions related to iron bioavailability and iron redox transitions. 

In 2007 and 2008, I led NSF-funded cruises on the R/V New Horizon in the eastern north Pacific 

to investigate the ecological role of iron in the deep chlorophyll maximum (DCM) of stratified 

oceanic regimes. DCM communities are ubiquitous in the lower euphotic zone of permanently or 

seasonally stratified oceanic systems, and important as sites of carbon export. Phytoplankton 

growth in the DCM is generally thought to be limited by the availability of both light and 

macronutrients, but little is known about the influence of iron availability as a potential co-limiting 

factor for these subsurface communities. Our field studies have documented widespread decoupling 

of the nitracline and ferricline, even in relatively dynamic coastal regimes (see Figure 1). 

Iron additions to DCM communities lead to a substantial shift towards a diatom-dominated 

assemblage, especially at elevated light levels, indicating that iron limitation may be especially 

acute when light levels change rapidly. These findings have important implications for the ironregulated 

response of DCM communities to shoaling of the nitracline as during eddy events or 

internal waves, with associated carbon export. 

My group actively contributes to the CCE-LTER (California Current Ecosystem, Long-Term 

Ecological Research) Program. The main objective of the CCE-LTER Program, achieved via both 

long-term ecological monitoring and dedicated process cruises, is to understand the coupling of 

physical, chemical and biological dynamics in the California Current ecosystem and, ultimately, 

system responses to long-term climate variability. Research in my group contributes to the overall 

goals of the CCE-LTER program by providing information about the distribution and supply of iron, a 

potentially limiting factor for and bottom-up control on phytoplankton growth. Our work on iron 

biogeochemistry in conjunction with CCE-LTER and CalCOFI (California Cooperative Oceanic 

Fisheries Investigations) has demonstrated that iron supply has a significant effect on macronutrient 

utilization and phytoplankton productivity and species composition in the Southern California 

Current, and studies of iron will continue to be an important component of our understanding of how 

the system responds to long-term climate variability. 

A new direction for my group is combining chemical information on iron speciation in seawater 

with genomic information on the iron acquisition capabilities of microorganisms to inform our studies 

of the biogeochemical cycling of iron in seawater. Recently we were able to document the existence 

of a novel iron uptake pathway in marine bacteria, which involves direct assimilation of heme iron 

complexes. This process has important implications for iron speciation in seawater and the role of

acteria in iron recycling in oceanic systems. We are continuing laboratory studies of microbial iron 

cycling in marine particle environments, including the colonial nitrogen-fixing cyanobacterium, 

Trichodesmium. 

Figure 1. (Left) Profiles of dissolved iron (blue triangles), chlorophyll fluorescence (green), and 

ISUS nitrate (orange) at CalCOFI station 93.40, 100 km off the CA coast, in July 2007. Note 

extensive de -coupling between the nitricline and ferricline at the base of the deep chlorophyll 

maximum layer. Iron and light addition incubation studies performed with this community under 

in-situ conditions revealed significant iron limitation of the phytoplankton assemblage (right). 

Recent Publications 

King, A.L. and K. Barbeau. 2007. Evidence for phytoplankton iron limitation in the southern California current 

system. Mar. Ecol. Prog. Ser. 342:91-104. 

Hopkinson, B.M, B.G. Mitchell, R.A. Reynolds, H. Wang, K.E. Selph, C.I. Measures, C.D. Hewes, O. Holm- 

Hansen and K.A. Barbeau. 2007. Iron limitation across chlorophyll gradients in the southern Drake Passage: 

Phytoplankton responses to iron addition and photosynthetic indicators of iron stress. Limnol. Oceanogr. 52: 

2540-2554. 

Kwasnik, M., K. Fuhrer, M. Gonin, K. Barbeau and F. Fernandez. 2007. Resolving power and radial ion 

distributions in a prototype resistive glass atmospheric pressure ion mobility spectrometer. Anal. Chem. 

79:7782-7791. 

Dupont, C.L., K. Barbeau and B. Palenik. 2008. Ni limitation and uptake in marine Synechococcus. Appl. 

Environ. Microbiol. 74: 23-31. 

Hopkinson, B.M. and K. Barbeau. 2008. Interactive influences of iron and light limitation on phytoplankton at 

subsurface chlorophyll maxima in the eastern North Pacific. Limnol. Oceanogr. 53: 1303-1318. 

Hopkinson, B.M., K.Roe and K. Barbeau. 2008. Heme uptake by Microscilla marina and evidence for heme 

uptake systems in the genomes of diverse marine bacteria. Appl. Environ. Microbiol. In press.

Jonathan Berger 

Research Geophysicist 

Email: jberger@ucsd.edu 

Phone: 42889 

Research Interests: Global seismological observations, geophysical instrumentation, deep ocean 

observing platforms, global communications systems. 

For the past several years, I have been working on 

an advanced SPAR buoy design to be used as an 

unmanned deep-ocean, moored observatory. The 

design requirements were based on a multi-year 

deployment at a mid-Atlantic site for 

multipurpose measurements (swell, meteorology, 

aerosols, seismology, ocean basin heat content, 

and detailed ocean structure. The platform 

concept, developed first by Technip as an offshore 

oil production platform, was scaled down for 

scientific use in partnership with Technip, and 

Glosten Associates. Called an Extended Draft 

Platform (EDP), the design will provide 

substantial power and bandwidth to the seafloor 

and a stable surface platform for instruments and 

communications. 

The EDP comprises an upper deck box, three 

columns and a lower pontoon with the structure 

behaving like a deep draft semi-submersible or 

spar buoy. The unique feature of the EDP is that 

the columns penetrate that deck, and the pontoon 

can be positioned just below the deck for construction, commissioning, and towing. In this 

configuration the draft is only about 4m. It will provide a stable platform with large deck space (up to 

300 m2) for science experiments and a total payload of over 30 metric tons. Compartments in the 

three extensions of the deck box are designed to hold all the power, communications and 

instrumentation equipment. Diesel/solar electric power in the range of 10 kW will be provided for the 

communications and oceanographic instrumentation systems with tanks to provide one-year between 

refueling. 

The EDP is tri-moored on a combination steel wire/polyester mooring designed to hold the EDP on 

station while a separate Electro-Optical cable is used for power and data transmission to the seafloor. 

The seafloor junction box will be supplied with at least 500 W of power. Communications and power 

delivery between seafloor instruments and the J-Box will be via ROV wet-mateable connectors on the 

J-Box. Communications between the J-Box and the EDP will be via fiber optic channels. On the 

EDP, C-band communication channels will be used for telemetry of at least 500 Mbytes/day from the 

platform to shore. Back-up communications systems will provide independent command and control 

channels in the event of failure of the principal communications channels. 

The expected weather and waves for four global sites for the 50-year extremes are shown in the figure 

below. (The vertical axis is in m/s, m, or seconds as appropriate.) The platforms should be designed

to operate in the 5-year extremes and survive the 50-year extremes. The wave dominant period of the 

extreme waves are an essential design specification for both EDP and discus designs. 

Using a model of the EDP and the 50-year extremes for the mid-Atlantic site with current, wind and 

waves aligned between a pair of mooring lines (0°), we find the worst case pitch predicted is

Wolfgang H. Berger 

Professor of Oceanography, emeritus 

Email address: wberger@ucsd.edu 


Research Interests: History of ocean research, history of the Quaternary, history of the 

Cenozoic ocean, mechanisms of climate change. 

Much of my research in recent years has focused on the last century of exploration of 

the ocean, with some emphasis on Scripps contributions. Results are summarized in a 

forthcoming book to be published by University Press (Berger, 2009). In the course of this 

work, I noted that several rather basic topics related to climate change have not received the 

attention they deserve. They are (1) potential rate of change of sea level as a function of state 

of climate, (2) the timing of the onset of widespread retreat of mountain glaciers (1850), (3) the 

sporadic appearance of well-defined cycles in the North Atlantic Oscillation, and (4) the timing 

of the evolution of modern baleen whales. 

The typical rate of change of sea level, as seen at the end of the last ice age, is near 1 m 

per century (that is why it took about 10,000 years to raise sea level by 100 m). Naturally, over 

shorter intervals within periods of ice collapse within the late Quaternary, rates are 

substantially higher. Unfortunately, the resolution is only on the scale of millennia, which 

means the maxima cannot be reconstructed on the scale of centuries. Even on the 1000-year 

time scale, however, a change of up to 2 m/century is not uncommon when ice ages are 

terminated (Berger, 2008a). There seems to be an upper limit to which sea level can readily 

move, somewhere near +10 m, judging from the history of the last 500,000 years. As far as the 

timing of mountain glacier retreat, it appears that drought was important in the northern 

Rockies (Berger, in press). A failure to reverse the retreat, presumably can be ascribed to 

general warming within the 20 th century. Beginning in the early 20 th century, the North Atlantic 

Oscillation is characterized by a strong cycle near 7.74 and a slightly lesser one at 5.8 (Berger, 

2008b). The origin of these cycles is not clear. Possibly they reflect forcing of inherent 

oscillations by outside factors stimulated by tides and solar variability. Whales acquired baleen 

sometime in the Oligocene, after the great cooling step that characterizes the end of the 

Eocene. It is suggested that, as a result of cooling in high latitudes and an opening of the Drake 

Passage, circumpolar winds and currents provided for a silicate-rich reservoir around the 

Antarctic, which could feed nutrients to upwelling regions (Berger, 2007). Silicate-rich 

upwelling provides for diatom growth and short food chains, a precondition for making 

filtering of plankton by warm-blooded animals worth the investment in energy. Silica-fed 

productive equatorial upwelling in the Pacific started in the Late Oligocene, as recorded in 

deep-sea sediments (Berger, 1973). 

Relevant Publications 

Berger, W.H., 1973. Cenozoic sedimentation in the eastern tropical Pacific. Bull. Geol. Soc. Am., 

84: 1941-1954. 

Berger, W.H., 2007. Cenozoic cooling, Antarctic nutrient pump, and the evolution of whales. In: 

D. Warnke, G.M. Filippelli, J.-A. Flores (eds.) Paleoceanography and Paleoclimatology of the 

Southern Ocean: A Synthesis of Three Decades of Scientific Ocean Drilling. Deep-Sea Res. II,

54, 2399-2421. 

Berger, W.H., 2008a. Sea level in the Late Quaternary: Patterns of variation and implications. 

Internat J. Earth Sciences, Springer Verlag, in press. 

Berger, W.H., 2008b. Solar modulation of the North Atlantic Oscillation: Assisted by tides? 

ASILOMAR Climate Symposium, March 2006. Quaternary International, 188, 24-30. 

Berger, W.H., 2009. Ocean – Reflections on a Century of Exploration. UC Press, Berkeley (in 

press). 

Berger, W.H., in press. On glacier retreat and drought cycles in Montana and Canada. 

ASILOMAR Climate Symposium, May 2007. Quaternary International.

Donna Blackman 


Email address: dblackman@ucsd.edu 


Research Interests: tectonic and magmatic processes that occur along plate boundaries with 

emphasis on oceanic spreading centers; deformation of minerals and the development of seismic 

anisotropy during mantle flow; hydroacoustic calibration experiments for nuclear test monitoring 

Geophysical investigations of oceanic spreading center processes continue to be the main 

focus of my research. The approaches I use vary both by design and in response to opportunities for 

seagoing experiments. In 2007/2008 my analyses incorporated data/results from deep sea drilling, 

shipboard mapping, gravity modeling, and seismic refraction/reflection. Further analysis of prior 

geophysical from an oceanic core complex on the Mid-Atlantic Ridge provided the basis for more 

in-depth modeling than had been applied to the area before. Including the effects of 3-D structure 

within the core complex, a revised gravity model that is consistent with drilling results was 

obtained. Similarly, the ground truth provided by the recovered drill core were used to guide new 

tomographic inversions of seismic velocity in the upper ~km of the domal core, which has been 

exposed by a detachment fault. Working with Graham Kent and Alistair Harding, a downward 

continuation method was tested on multi-channel seismic data. We confirmed that additional 

insight into structure in the shallowest part of the section could be obtained with the method and 

this influences details of the deeper structure required to explain the full data set. 

Modeling of mantle flow, led by postdoc Nick Harmon, addresses how variation in the 

distance between the Tonga trench and the Lau basin backarc spreading centers can influence 

patterns of melting in the mantle wedge above the subducting plate. Effects of water on the melt 

production have been explored as have a number of other physical parameters that we aim to relate 

to geochemical and petrological observations made by colleagues working at the Ridge 2000 

Integrated Studies Site on the Eastern Lau Spreading Center. 

In my third year as chair of the NSF Ridge 2000 program (http://www.ridge2000.org), I 

worked with colleagues and members of the R2K Office at SIO to facilitate interdisciplinary 

research on oceanic spreading centers. This research involves biologists, chemists, geophysicists, 

geologists, and oceanographers, all working to understand the interplay between processes that 

control rifting and hydrothermal venting along spreading centers. A major effort this year was to 

document the Program's progress to date (2001-2007) so that a review panel could assess results 

and decide if the R2K should continue for a full term. The Program was renewed and will continue 

funding research through 2012, so the normal rotation of the R2K Office to a new host institution 

and Chair will occur in November this year. 

Catherine de Groot-Hedlin to the lead on our hydroacoustic work this year, modeling sound 

propagation and losses along the source-receiver paths from our 2006/7 experiment across the 

Antarctic Circumpolar current boundary. Our paper on this work is under review this summer.

Lower panel of figure shows Mantle Bouguer gravity anomaly map where Mid-Atlantic Ridge 

segments are offset by Atlantis transform fault. Grey contours show bathymetry at 500 m intervals. 

Atlantis Massif oceanic core complex on the west flanks of the eastern ridge-transform intersection 

is shown in the upper panels. At left are bathymetry (color) and models of interface geometry 

where density contast between upper (baslt) and lower (gabbroic) crust is assumed. Model 1 results 

in removal of too much mass (the black anomaly on the west flank in the lower panel) whereas 

Model 2 can explain much of the Mantle Bouguer (upper right panel; color scale same as in b). 

Castelnau, O., D.K. Blackman, R.A. Lebensohn, and P. Ponte, “Micromechanical modelling of the 

viscoplastic behavior of Olivine”, J. Geophys. Res., 2008 in press. 

Blackman, D.K., G.D. Karner, and R.C. Searle, “Three-dimensional structure of oceanic core 

complexes: effects on gravity signature and ridge flank morphology, Mid-Atlantic Ridge 30 o N”, 

G 3 , 9, doi:10.1029/2008GC001951, 2008.

Yehuda Bock 

Research Geodesist and Senior Lecturer 

Email address: ybock@ucsd.edu 


Research Interests: space geodesy, crustal deformation, natural hazards, GPS seismology, GPS 

meteorology, GIS and Information Technology 

Yehuda Bock’s research focuses on space geodetic innovations, which he applies to a wide range 

of geophysical studies. He has developed new methods for analyzing GPS data (“instantaneous 

positioning”) that can be used for precise real-time monitoring of displacements at high rates (1- 

50 Hz), in combination with traditional seismic instruments. In Mattia et al. [2008] we used 

instantaneous positioning of 15 s GPS data to define the dimensions and the characteristics of the 

shallow plumbing system of the 2005-2006 

eruption of the Mt. Augustine (Alaska) 

stratovolcano as a massive migration of 

magmatic fluids from depth under the effect 

of gas overpressure. Volcanic eruptions are 

usually preceded by measurable signals of 

growing unrest such as increase in 

seismicity and ground deformation. With 

Yehuda’s real-time methods it is possible to 

identify precursors of a possible renewal of 

the volcanic activity and to distinguish 

between an eruptive activity characterized 

by an intrusion and a migration of magma stored in the main conduits. 

In Bassis et al. [2007], we used 2 Hz-sampled GPS data to monitor the tip of a propagating 

rift on the Amery Ice Shelf over 3 consecutive annual field seasons. Instantaneous positioning 

allowed us to monitor a network of receivers that were all subject to motion (i.e., there was no 

stable reference available). This study confirmed that rift propagation is episodic, allowed us to 

compare icequakes with earthquakes, and provided a first step in understanding the details of 

meso-scale physics that controls rift propagation over moderate spatio-temporal scales. 

In Kogan et al. [2008] we monitored the structural response of the Verrazano-Narrows 

Bridge to 2004 New York City 

Marathon runners using a 

Kalman filter analysis of data 

collected by 5Hz GPS receivers 

and 100Hz force-balance 

accelerometers (FBA). The vibrations excited by runners are small in terms of displacements, yet 

large in terms of accelerations (favoring FBA). On the other hand, the slow deflection under a 

load of runners is large in terms of displacements while the corresponding accelerations are very 

small (favoring GPS). The optimal sensitivity is obtained by fusing both data sets, which Yehuda 

and graduate student Brendan Crowell are applying to earthquake early warning systems. 

In Luttrell et al. [2007] we used instantaneous positioning to rapidly and efficiently measure 

the current elevation of observed ancient shoreline features to constrain the model parameters of 

plate thickness and relaxation time in order to estimate the vertical rebound of the Lake Cahuilla 

area since the last lake fall. The lake cycle causes significant Coulomb stress perturbations on the 

southern San Andreas fault, comparable to stress magnitudes known to have triggered events on 

other regional faults. This is important for assessing seismic hazard on the southern San Andreas 

and San Jacinto faults, which have not had a major rupture in the last 300 years.

Yehuda also directs the Scripps Orbit and Permanent Array Center (http://sopac.ucsd.edu), 

with a staff of 4 programmers who are engaged in several multi-year IT projects for NASA and 

NOAA. As an example, we have developed the Pocket GPS Manager (PGM) software (see figure 

below) - a wireless PDA application designed to eliminate the use of paper GPS field logs via 

direct communication with a set of centralized information services, for planning, collecting, 

analyzing, interpreting, and publishing GPS-based projects. It has been used in a number of 

CSRC projects (http://csrc.ucsd.edu), a project in Louisiana in response to Hurricane Katrina, and 

IGPP-led field work in the Imperial Valley (http://sopac.ucsd.edu/projects/impvall2008.html). 

Recent Publications: 

Aydin, G., Z. Qi, M. E. Pierce, G. C. Fox, and Y. Bock (2007), Architecture, performance, and 

scalability of a real-time global positioning system data grid, Phys. Earth and Planet. 

Interiors, 163, 347-359, doi:10.1016/j.pepi.2007.04.012. 

Bassis, J. N., H. A. Fricker, H. A., R. Coleman, Y. Bock, J. Behrens, D. Darnell, M. Okal, and J.- 

B. Minster (2007), Rift propagation, seismicity and deformation associated with ice shelf rift 

propagation, J. Glaciology, 53(7), 523–536. 

Kogan, M. G., W-Y. Kim, Y. Bock, and A. W. Smyth (2008), Load response on the Verrazano 

Narrows Bridge during the NYC Marathon revealed by GPS and accelerometers, Seismo. 

Res. Lett., 79(1), 12-19. 

Luttrell, K., D. Sandwell, B. Smith-Konter, B. Bills, and Y. Bock (2007), Modulation of the 

earthquake cycle at the southern San Andreas fault by lake loading, J. Geophys. Res., 112, 

B08411, doi:10.1029/2006JB004752. 

Mattia, M., M. Palano, M. Aloisi, V. Bruno, and Y. Bock (2008), High rate GPS data on active 

volcanoes: An application to the 2005-2006 Mt. Augustine (Alaska, USA) eruption, Terra 

Nova, 20, 134–140, doi: 10.1111/j.1365-3121.2008.00798.x. 

Wdowinski, S., B. Smith, Y. Bock, D. Sandwell (2007), Diffuse interseismic deformation across 

the Pacific–North America plate boundary, Geology, 35(4), doi:10.1130/G22938A.1, 311- 

314.

Steven Cande 

Professor 

Email address: scande@ucsd.edu 


Research Interests: Global plate reorganizations, tectonic evolution of the Pacific and Indian 

Oceans, motion between East and West Antarctica, tectonics of the Western Ross Sea, source 

of marine magnetic anomalies, geomagnetic polarity timescale, paleo-intensity variations of 

the geomagnetic field. 

The focus of my recent research has been analyzing Cenozoic plate motions in the 

Indian and South Pacific ocean basins using marine magnetic anomalies, swathmap bathymetry 

and satellite gravity data. A particular emphasis has been on improving the plate motions 

around the circuit linking the Australia, Pacific and Antarctic plates. This plate circuit is very 

important because it constrains motion on the complex plate boundary between the Australia 

and Pacific plates, which includes the Macquarie Ridge and Alpine Fault in New Zealand, and 

constrains motion between East and West Antarctica. By analyzing the magnetic anomalies 

and fracture zones on the Pacific-Antarctic ridge and Southeast Indian ridge we identified a 

period of time in the mid-Cenozoic, from 45 to 28 million years ago, when there was motion 

between East and West Antarctic that caused extension in the western Ross Sea and seafloor 

spreading in the Adare Basin just north of the Ross Sea (Figure 1). 

Figure 1. Left: Magnetic anomalies, fractures zones, spreading ridges (red), and triple junction 

traces (green) in the Southwest Pacific. Right: Reconstruction of the Southwest Pacific to 43 

Million years. Note the rotated position of the South Island of New Zealand relative to the North 

Island due to motion on the Alpine Fault and the closure of the basins in the western Ross Sea 

due to motion between East and West Antarctica. 

For several years my students and I, in collaboration with Joann Stock and students at 

Caltech, have been collecting magnetics, gravity and swathmap bathymetry data on the NSF 

operated icebreaker Nathaniel Palmer during transits of the South Pacific in which the ship is

epositioned between New Zealand and Chile before research projects in Antarctica. These 

data, many of which have been collected on the Menard Fracture Zone, have been used to 

construct a very detailed model of the pattern of seafloor spreading on the Pacific-Antarctic 

Ridge during the last 45 million years. 

Figure 2. Swathmap and magnetics data collected along the Menard Fracture Zone on transits 

of the R/VIB Palmer between 1998 and 2008. From Croon et al. (2008) 


Cande, S.C. and J. M. Stock, 2004, Pacific-Antarctic-Australia motion and the formation of the 

Macquarie Plate, Geophys. J. Int., 157, 399-414. 

Davey, F.J., S.C. Cande , and J.M. Stock, 2006. Extension in the western Ross Sea region – links 

between Adare Basin and Victoria Land Basin, Geophys. Res. Letts., 33, 

doi:10.1029/2006GL027383. 

Downey, N. J., J. M. Stock, R. W. Clayton, and S. C. Cande, 2007, History of the Cretaceous 

Osbourn spreading center, J. Geophys. Res, 112, doi:10.1029/ 2006JB004550. 

Croon, M. B., S. C. Cande, and J. M. Stock, 2008, Revised Pacific-Antarctic plate motions and 

geophysics of the Menard Fracture Zone, Geochem. Geophys. Geosyst., 9, 

doi:10.1029/2008GC002019.

Pat Castillo 

Professor of Geology 

Email address: pcastillo@ucsd.edu 


Research Interests: geochemistry and petrogenesis of magmas produced within and along divergent 

and convergent margins of tectonic plates; magmatic and tectonic evolution of continental margins; 

mantle geodynamics 

My research activities focus on the relationship between mantle convection and evolution on 

the one hand and magma production associated with the birth of and interaction between plate tectonic 

plates on the other. These activities generally involve marine or terrestrial investigation of a study area, 

sampling of its igneous rocks and detailed laboratory analysis of the mineralogy, texture, major-trace 

element composition, and Sr-Nd-Pb isotopic characteristics of the samples collected. In May 2008, P. 

Lonsdale, graduate students J. Klausner and D. Ebuna, scientific collaborators from San Diego State 

University and Mexico, and I investigated the morphology and structure as well as collected samples in 

situ from the seafloor of the Gulf of California using the ROV Jason aboard RV Atlantis. This is part of 

our project to study the tectonic and petrologic evolution of the Gulf of California, a nascent ocean 

basin along the western margin of North America. I am currently waiting for the analytical results on 

the collected samples in order to select representative ones for more detailed isotopic analysis. As part 

of this project, I have recently investigated the occurrence of post-subduction, arc-related magmatism 

in the peninsular Baja California, Mexico (Castillo, 2008). Data show that the continuance of arcrelated 

magmatism after the cessation of subduction there is most probably related to large-scale 

tearing of the subducted oceanic plate underneath the proto-Gulf of California. This conclusion is 

different from the widely popular view that the post-subduction, arc-related magmatism in Baja 

California is due to the opening of small windows in the subducted plate directly underneath the 

peninsula. 

I am also currently investigating the samples we dredged, in collaboration with S. Cande and 

K. Panter from Bowling Green State University, from a number of volcanic seamounts in the Adare 

Basin, northwestern Ross Sea, and on the adjacent continental shelf of north Victoria Land using the 

RVIB NB Palmer in Austral summer 2006-2007. Preliminary lithologic, compositional and age data 

suggest that the Adare Basin seamount volcanism is coeval and petrogenetically akin to continental 

volcanism in West Antarctica, and thus expands the known extent of Cenozoic alkaline magmatism 

associated with the West Antarctic rift - one of the major active continental extensional zones on Earth 

(Panter and Castillo, 2007). Interestingly, they are also similar to other continental intraplate lavas in 

southwest Pacific and this petrologic similarity suggests that there is an inherent connection between 

their mantle sources. Moreover, the coupled extensional history of the oceanic and continental sectors 

in the northern Ross Sea, along with the broadly coincident age of their volcanic activities, strongly 

suggest that both continental and oceanic volcanism were triggered by the same fundamental 

mechanism. 

Graduate student L. Tian, post-doctoral fellow D. Ham, D. Hilton, J. Hawkins, and I are currently 

wrapping up our project in the Lau Basin, southwest Pacific (Tian et al., in press). Data show that most of 

the lavas from the northern Lau Basin are tholeiitic basalts that are similar to mid-ocean ridge basalts 

(MORB) and Central Lau Basin spreading center lavas. However, a few lavas, particularly those from 

intraplate seamount volcanoes, show some similarities with lavas from the Tonga volcanic arc to the east

and those from the Samoan Islands to the north, suggesting that the mantle beneath the northern Lau 

Basin has been influenced by materials subducted along the Tonga Trench and by the mantle source of 

ocean island basalts (OIB). The influence of an OIB mantle source on the northern Lau Basin mantle has 

previously been suggested by anomalously high 3 He/ 4 He ratios in some of these lavas. 

Finally, L. Tian, D. Ham, D. Hilton, and I are currently pursuing a combined petrologic and noble 

gas investigation of lavas previously dredged from fossil spreading centers in eastern Pacific. In contrast 

to the copious volcanism along active spreading centers, which is caused by adiabatic decompression 

melting of the upper mantle, the origin of volcanism at abandoned spreading centers is an enigma. For 

example, Guadalupe Island and Sara, Rosana, Rosa, and Nithya seamounts are volcanoes built on 

abandoned spreading centers between 26°N and 29°N in the eastern Pacific offshore Baja California. 

Preliminary results show that lavas from these volcanoes are predominantly mildly to moderately alkalic 

basalts and their differentiates, and these are compositionally different from tholeiitic MORB from the 

East Pacific Rise (EPR). Results also show that the composition of fossil spreading center lavas overlaps 

with those of seamounts offshore southern California and tholeiitic to alkalic seamounts near the EPR. 

Together, these intraplate lavas define a compositional continuum ranging from MORB-like to OIB-like. 

Thus our preliminary results suggest that volcanism at abandoned spreading centers and intraplate 

volcanism in eastern Pacific as a whole result from a complex interplay between mantle melting dynamics 

and lithospheric tectonic processes. 


Castillo, P.R., 2008, The origin of the adakite - high-Nb basalt association and its implications for postsubduction 

magmatism in Baja California, Mexico, Bull. Geol. Soc. Amer., 120: 451-462. 

Panter, K.S. and P.R. Castillo, 2007, Petrogenesis and source of lavas from seamounts in the Adare 

Basin, Western Ross Sea: Implications for the origin of Cenozoic magmatism in Antarctica. in 

Antarctica: A Keystone in a Changing World – Online Proceedings of the 10 th 

ISAES X, edited by A.K. 

Cooper and C.R. Raymond et al., USGS Open-File Report 2007-1047, Extended Abstract 069, 4 p. 

Tian, L, Castillo, P.R., Hawkins, J.W., Hilton, D.R., Hanan, B.B. and A.A. Pietruszka, 2008 (in press) 

Major and trace element and Sr-Nd isotope signatures of the mantle beneath the Central Lau Basin: 

Implications for the nature and influence of subduction components. J. Volc. Geotherm. Res.

Christopher D. Charles 

Professor of Oceanography and Paleoclimatology 

Email address: ccharles@ucsd.edu 


Research Interests: Reconstruction of climate history from ice ages to present, in geological 

materials such as corals and deep sea sediments; isotope tracers in the ocean and atmosphere 

Over the past year, my research has been devoted to several specific themes dealing 

with the geological archives of recent climate change and carbon cycling. 

One steady theme for me has been the coral record of interannual climate variability. 

Former SIO graduate student Kim Cobb and I have been working to develop the record of the 

El Niño/Southern Oscillation (ENSO) phenomenon fossil corals from the Line Islands (Central 

Pacific). Work over the past year has concentrated on building a quasi-continuous record over 

the last millennium. Results suggest that the ENSO phenomenon was fairly insensitive to 

external forcing (solar, volcanic, etc.), or, perhaps more precisely, the forcing was not strong 

enough to alter the weakly chaotic behavior of ENSO. We have also begun to fill out the 

observations of ENSO through the late Holocene—a time of relatively strong insolation 

forcing in the tropics--using a collection of corals that spans the last 6500 years. The results 

will ultimately contribute to the debate on whether ENSO can be forced externally (with either 

natural or anthropogenic forces) and whether the statistics of the phenomenon themselves 

influenced the evolution of global climate. 

Another current theme is the deep sea sediment record of the ocean's large scale 

overturning circulation. This circulation has often been implicated in the abrupt climate 

changes that punctuated the late Pleistocene epoch, but the explanations for these dramatic 

climate events will remain largely speculative until there is a legitimate picture of "what 

happened when" in the deep ocean. Over the past year, I was able to use existing deep sea 

sedimentary records to demonstrate that the vertical gradient in Southern Ocean properties 

(both temperature and nutrients) followed North Atlantic climate events faithfully for at least 

the last 200,000 years. This observation carries a number of implications for the “abrupt 

change” in ocean circulation and climate, while also offering an avenue for linking the 

millennial scale chronologies of terrestrial and marine archives. Along similar lines, graduate 

student Jenna Munson investigated the records of radiocarbon in benthic foraminifera from the 

South Atlantic ocean. She found that the vertical structure (water mass origin) of the mid-depth 

Atlantic ocean was indeed profoundly altered during the last ice age. It also suggests that the 

change to modern conditions was likely accomplished early in the deglaciation process. 

Graduate student Lydia Roach capitalized on the unique sedimentary environment of the Santa 

Barbara Basin to develop of radiocarbon record of bottom water ventilation spanning the last 

few centuries. 

A third theme involves the cycling of carbon over the Pleistocene ice ages. The 

mystery of what caused the large natural, glacial-interglacial fluctuations of atmospheric 

carbon dioxide has endured for over 20 years, but if the enigma could be solved, the 

consequence would be a better understanding of how (and at what rate) the ocean might soak 

up anthropogenic CO2. Our lab's contributions over the past year, along with various

collaborators, have essentially dealt with the record of nutrient cycling and the biological pump 

of carbon. For example, current graduate student Patrick Rafter is attempting to disentangle the 

various imprints on the marine nitrogen isotope budget of the equatorial Pacific. 

Current and planned submissions 

Charles, Pahnke, Zahn, Ninnemann, Hodell “Late quaternary dynamics of the Southern Ocean 

chemical divide“(for submission to Quaternary Sci. Reviews): 

Munson, Charles, Kasgarian, Slowey, “The utility of paired benthic-planktonic foraminiferal 

radiocarbon ages assessed from a South Atlantic depth transect” (Paleoceanography) 

Munson, Charles, Kasgarian, Slowey, “Ventilation of the South Atlantic since the last ice age: the 

evidence from foraminiferal radiocarbon” (Earth and Planetary Science Letters) 

Cobb, Charles, Cheng, Edwards, “ENSO variability through the medieval warm period and the 

Little Ice Age.” (in preparation for Science) 

Rafter, Charles, Sigman “The isotopic composition of nitrate across the equatorial Pacific: 

denitrication, fixation, and mixing” (for submission to Global Biogeochemical Cycles). 

Roach, Charles, Field Guilderson “Ventilation of the Santa Barbara Basin over the last two 

centuries” (for submission to J. Geophys. Res.)

Catherine Constable 

Professor of Geophysics 

Email: cconstable@ucsd.edu 

Phone: 858 534 3183 

Research interests: Paleomagnetism and geomagnetism, applied to study of long and short term 

variations of the geomagnetic field; inverse problems; statistical techniques; electrical conductivity 

of the mantle; paleo and rock magnetic databases 

Three ongoing research projects are targeting (i) geomagnetic field behavior during the 

Holocene time period (post doc, Fabio Donadini, and collaborator Monika Korte of GeoForschungs 

Zentrum, Potsdam), (ii) the magnetic field on million year time scales (PhD student Leah Ziegler, and 

Adjunct Professor Catherine Johnson) and (iii) electromagnetic induction studies from low-Earthorbiting 

satellites (PhD students, Joseph Ribaudo and Lindsay Smith). Other work includes the 

development with Anthony Koppers and Lisa Tauxe of flexible digital data archives for magnetic 

observations of various kinds under the MagIC (Magnetics Information Consortium) database 

project. 

The Holocene Geomagnetic Field: The geomagnetic field has been measured at a variety 

of locations ever since the development of the first compasses, and direct observations on Earth’s 

surface and (more recently) from low-earth orbiting satellites have led to excellent time-varying 

descriptions of the field for the past 400 years. Our recent work has focussed on improving the quality 

of millennial scale time varying geomagnetic field models for the past 3 kyr and extending existing 

models back to 10kyr. Major effort has been invested in compiling and evaluating comprehensive 

paleomagnetic data sets; new models for 0-3 ka also incorporate constraints from the 1590-1990 AD 

era of direct observations. The results of these endeavors are now being used to study the evolution 

of the South Atlantic Anomaly, currently manifest as a region of unusually low field strength, and 

to evaluate the significance of some apparently rapid changes in the field that have been named 

archeomagnetic jerks. 

Figure 1(a) 

0-1 Ma Global Paleointensity Distribution 

Figure 1(b) 

0-1 Ma Temporal Paleointensity Distribution 

4.96 

4.34 

3.72 

3.1 

2.48 

1.86 

1.24 

0.62 

Figure 2: PINT03 gives distribution, with dashed 

lines as 95% confidence bounds, of absolute 

paleointensity data for 0-1 Ma. SINT2000 curve 

reflects smoothed distribution from global averaged 

sediment records. 

The Magnetic Field on Million year Time Scales: Graduate student Leah Ziegler has been 

investigating the feasibility of extending time-varying field models to much longer (million year) 

time scales by combining directional and relative paleointensity data from marine sediments, with 

directions and absolute paleointensity data recovered from lava flows. A first step in this process

has been a study of the robustness and limitations of the 0-1 Ma absolute paleointensity data. Figure 

1 shows the global distribution of 0-1 Ma absolute paleointensity plotted as density of observations 

on a log scale. Red (purple) values show areas with a high (low) concentration of data. White 

areas have no data. In Figure 1(b) paleointensity data are converted to equivalent virtual axial 

dipole moment and plotted as a function of age. The uneven temporal and spatial sampling seen 

in Figure 1 has been evaluated, and the average paleomagnetic axial dipole moment over 0–1 Ma 

is 7.26±0.14 × 10 22 Am 2 , but the distribution of moments has an unusual bimodal distribution 

arising from long term variations in the geomagnetic field. Similar structure is seen in subdued 

form in the globally-averaged record from sediments which typically average variations over as 

large a time interval as 30 kyr (Figure 2). Current work is focussed on calibrating individual relative 

paleointensity time series from marine sediments to recover continuous dipole moment variations 

for the 0–1 Ma time interval. 

Electromagnetic Induction Studies Using Satellite Observations: Induced magnetic fields 

in Earth’s crust and mantle arise from temporal variations in the external part of the magnetic 

field, and these can be investigated using both ground and satellite observations. Graduate student 

Joseph Ribaudo is developing numerical tools for global geomagnetic induction modeling via 

a commercially-available, general purpose, finite element modeling package called FlexPDE that 

uses flexible, scripted, finite element models. The modeling is performed in both time and frequency 

domains, and has been validated against known solutions to 3D steady state and time-dependent 

problems. The strength of the magnetic field generated by the magnetospheric ring current is 

known to vary as a function of local time, giving it an asymmetric spatial structure. Electromagnetic 

C-responses estimated from satellite data under the assumption that primary and induced fields are 

symmetric in structure are known to be biased with respect to local time, leading to associated 

uncertainties in mantle electrical conductivity. The scripted programming approach allows forward 

modeling of the global induction problem with realistic primary field structure, 3D Earth conductivity, 

and rotation, to study the influence on C-responses and provides for ready visualization of 

magnetic and electric fields throughout the modeling domain. 


Korte, M., & C.G. Constable, Spatial and temporal resolution of millennial scale geomagnetic field 

models, Advances in Space Research, 41, 57–69, doi:10.1016/j.asr.2007.03.094, 2008. 

Johnson, C.L., C.G. Constable, L. Tauxe, R. Barendregt, L.L. Brown, R. Coe, P. Layer, V. 

Mejia, N.D. Opdyke, B. Singer, H. Staudigel, & D. Stone, Recent Investigations of the 0- 

5 Ma Geomagnetic Field recorded by Lava Flows, Geochem. Geophys. Geosyst., 9, Q04032, 

doi:10.1029/2007GC001696, 2008. 

Genevey, A., Y. Gallet, C.G. Constable, M. Korte, & G. Hulot, An upgraded compilation of 

geomagnetic field intensity data for the past ten millennia, Geochem. Geophys. Geosyst., 9, 

Q04038, doi:10.1029/2007GC001881, 2008. 

Ziegler, L., C.G. Constable, & C.L. Johnson, Testing the robustness and limitations of 0–1 Ma absolute 

paleointensity data, Phys. Earth Planet. Inter., 170, 34–45, doi:10.1016/j.pepi.2008.07.027, 

2008. 

Gee, J.S., L. Tauxe, & C. Constable, AMSSpin – A LabVIEW program for measuring the 

anisotropy of magnetic susceptibility, Geochem. Geophys. Geosyst., 9, Q08Y02, doi: 10.1029/ 

2008GC001976, 2008.

Steven Constable 


Email: sconstable@ucsd.edu 

Phone: 42409 

Research interests: 

Marine EM methods, conductivity of rocks, satellite induction studies 

Steven Constable is the lead PI for the SIO Marine EM Laboratory, which currently consists of 

project scientist Yuguo Li, postdoctoral scholar Kerry Key, and PhD students Karen Weitemeyer, David Myer, 

and Brent Wheelock. Kerry has accepted an Assistant Research Scientist position at IGPP, effective Fall 

2008, so next year his work will be represented in the Annual Report under his own name. 

As the name suggests, much of the lab’s work is involved in developing and using marine EM 

methods. In August this year we carried out marine magnetotelluric (MT) studies in India, in and around the 

Gulf of Kutch just south of Pakistan in the northwest corner of the country. The objective is to map sediments 

underneath basalts at the edge of the Deccan Traps. This was a challenging project to say the least. Tidal 

currents in the Gulf were very swift and often filled the seafloor instruments with sediment, weighing them 

down and preventing their release. We made 39 deployments and 32 recoveries, although one instrument was 

lost in the ship’s propeller during recovery. Some instruments eventually shed the entrained sediment and 

floated to the surface, one of which we recovered at the end of the cruise and two of which were recovered by 

fishermen after we left the project. Work to interpret the data is ongoing. 

Figure 1. Recovering seafloor MT instruments in the murky waters of the Gulf of Kutch. 

Part of the funding for the group comes from a consortium of 32 oil companies (the Scripps Seafloor 

Electromagnetic Methods Consortium) which are interested in developing marine EM methods for offshore 

exploration. Many of our instrument trials for this work are carried out in the San Diego Trough, a 1,000 m 

deep graben with sedimented seafloor just a few hours transit from our marine facility in Point Loma. Over 

the years we have collected a useful suite of MT sties and controlled source EM (CSEM) data which we 

have used to image the geological structure of the Trough. One of the MT lines was co-located with a 

deep-towed gravity line collected in 1995 by Mark Zumberge and Jeff Ridgway (Mark’s student at the time). 

The combined MT, CSEM, and gravity interpretations, along with a nearby USGS seismic reflection profile, 

are shown in Figure 2. The gravity, CSEM, and MT all agree on a sediment thickness in the Trough of about 

3.5 km. Both the gravity and MT suggest that the Coronado Bank is a sedimentary, rather than basement, 

feature.

Depth (km) 

0 

1 

2 

3 

4 

5 

6 

S06 

♦ 

seismic multiple 

S07 

♦ 

low 

S02 

S09 

S05 

A02 s10 s11 S08 S03 

♦ 

♦ ♦ ♦ ♦ ♦ ♦ 

♦ 

2700 

2100 

2300 

20 25 30 35 40 45 50 55 

Horizontal Position (km) 

2400 

Figure 2. Image of the San Diego Trough obtained from marine EM, gravity, and seismic data. The color 

map is an inversion of MT data from sites S01 to S06. The vertical color bar is a 3-layer model based on a 

marine CSEM sounding oriented along the axis of the Trough. Blue overlay is a gravity model from Ridgway 

and Zumberge, along with densities in kg/m 3 . From Constable et al. (2008). 

The three technicians and two engineers who work in the Marine EM Laboratory have spent much 

of the year developing, building, and testing instruments for an upcoming series of cruises in the Gulf of 

Mexico and offshore California. The first project, to be carried out during October in the Gulf, is to map gas 

hydrate in the seafloor. There is much interest in marine hydrates, since they may variously be viewed as a 

hydrocarbon resource, a source of greenhouse gases, and a natural hazard. However, very little is known about 

the total amount of hydrate stored in marine sediments, and EM methods may be the only way of assessing 

this (the hydrate is more resistive than the host sediments). The second project is to augment a land MT 

survey being carried out by German colleagues to study the San Andreas fault zone near Parkfield. During 

November–January we will extend the land arrays 200 km offshore to study the interaction of the stalled slab 

and underplated crust with the plate boundary fault zone. One hypothesis is that fluids migrating into the base 

of the fault are responsible for non-volcanic tremor observed near Parkfield. 

Further information can be found at the lab’s website, http://marineemlab.ucsd.edu/ 


Constable, S., Geomagnetism, in Treatise on Geophysics, Volume 5, edited by G. Schubert and M. Kono, 

Elsevier, doi:10.1016/B978-044452748-6.00092-4 , 237–276, 2007. 

Li, Y., and J. Pek, Adaptive finite element modeling of two-dimensional magnetotelluric fields in general 

anisotropic media, Geophysical Journal International, accepted, 2008. 

Constable, S., K. Key, and L. Lewis, Mapping offshore sedimentary structure using electromagnetic methods 

and terrain effects in marine magnetotelluric data, Geophysical Journal International, accepted, 2008. 

2700 

S01 

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2350 

2100 

Ωm 

10,000 

1,000 

100 

10 

1 

0.1

J. Peter Davis 

Specialist 

Email: pdavis@ucsd.edu 

Phone: 4-2839 

Research Interests: time series analysis, geophysical data acquisition 

Peter Davis’s research responsibilities at IGPP center upon monitoring the scientific 

performance of Project IDA's portion of the Global Seismographic Network (GSN), a 

collection of 41 seismographic and geophysical data collection stations distributed among 25 

countries worldwide. IDA’s core philosophy that data integrity may best be maintained by 

keeping network managers in close contact with data consumers has proven well-justified over 

the 30+ years of IDA’s existence. IGPP is the perfect venue for IDA personnel to interact 

directly with many scientists who use GSN data on a daily basis. 

The GSN is an ideal instrument for determining many of the Earth’s large-scale 

geophysical properties. Dr. Davis recently began collaboration with IGPP’s Guy Masters to 

refine measurements of the frequency and attenuation rate of the Earth’s radial normal modes. 

The huge Sumatra-Andaman Islands earthquake of 2004 excited these modes to amplitudes 

larger than ever observed by modern digital seismometers. Using GSN data, Davis and 

Masters measured the oscillation frequency of the gravest of them, 0S 0, to an accuracy of better 

than 1ppm. This value differs by 7 nHz from a value that has remained unchallenged since it 

was published 28 years ago in the Ph.D. thesis work of an IGPP graduate student, Mark 

Riedesel. Knowing the frequency of 0S 0 more accurately will place tighter constrains on largescale 

Earth models. 

Figure 1. Schematic of the motion of free 

oscillations 0S2, 0T2, 0S3, and 0S0 

superimposed on a spectrum computed 

from 240 hours of vertical seismic data 

recorded at Geoscope station CAN 

(Canberra, Australia) following the 

Sumatra-Andaman Isl. earthquake. Figure 

from Park et al. (2005b), courtesy of G. 

Roult. 

Some of Peter Davis’s other recent work utilized tidal signals to evaluate the accuracy 

of instrument response information published by the GSN. Investigators use this information 

to remove from recorded data the frequency-dependent sensitivity of sensors so that they may 

study true ground motion and its underlying physical causes. All GSN network operators 

including IDA supply this response information along with the seismological time series. 

Because tides are a continuous background signal observable at nearly all GSN stations not at

high latitudes, they are ideal for checking the validity of instrument response over the lifetime 

of the network. Using information collected by satellites about tidal flow of water in the ocean 

basins, scientists can now model the effect of tides very accurately at any point on the Earth’s 

surface. With programs provided by Duncan Agnew of IGPP, Pete computed the tidal signal 

at all GSN stations to the accuracy required for validating their reported instrument response. 

This technique was useful both for checking instrument response and for examining 

long term behavior of the network’s sensors. Figure 2 shows results for station PFO, the GSN 

station locally operated by IGPP. As the IDA flagship station, this site serves as a testbed for 

all new generations of devices to be deployed throughout the network, so equipment turnover 

is particularly high here. Data segments varying from 60-180 days were used to compare the 

recorded tidal signal with what was predicted from the ocean models. If the computations 

agreed, all points should have unity relative amplitude in this plot. For PFO, this ideal was 

approached from mid-2002 onward. In the first half of the decade, the results were close but 

slightly higher, then lower than what is desirable. Late in 2001, the published response 

information was highly inaccurate and will have to be corrected. 

Figure 2: Measurements of the relative amplitude (ratio of observed to predicted 

amplitude) of the principal lunar tide M2 at GSN station PFO (Pinyon Flat, CA). 

Vertical dashed lines represent times when equipment was changed and a re-calibration 

procedure, performed. 


Davis, P., and J. Berger, Calibration of the Global Seismographic Network using tides, Seis. Res. 

Lett., 78, 454-459, 2007. 

Davis, P., M. Ishii and G. Masters, An assessment of the accuracy of GSN sensor response 

information, Seis. Res. Lett., 76, 678-683, 2005. 

Park, J., R. Butler, K. Anderson, J. Berger, H. Benz, P. Davis, C.R. Hutt, C.S. McCreery, T. 

Ahern, G. Ekström, and R. Aster, Performance review of the Global Seismographic Network 

for the Sumatra-Andaman megathrust earthquake, Seis. Res. Lett., 76, 331-343, 2005. 

Park, J., T.-R. Song, J. Tromp, E. Okal, S. Stein, G. Roult, E. Clevede, G. Laske, H. Kanamori, P. 

Davis, J. Berger, C. Braitenberg, M. Van Camp, X. Lei, H. Sun, H. Xu and S. Rosat, Earth’s 

free oscillations excited by the 26 December 2004 Sumatra-Andaman earthquake, Science, 

308, 1140-1144, 2005. 

Berger, J., P. Davis, and G. Ekstrom, Ambient Earth Noise: a survey of the Global Seismic 

Network, J. Geophys. Res., 109, B11307, 2004.

Catherine de Groot-Hedlin 

Associate Project Scientist, email: chedlin@ucsd.edu, Phone extension: 4-2313 

Research Interests: Acoustic propagation modeling with application to infrasound and 

hydroacoustics; application of hydroacoustics and infrasound to nuclear test-ban 

verification; use of dense seismic networks to analyze infrasound signals; application of 

infrasonic signals to hazard monitoring. 

Infrasound: A primary goal in infrasound research is to understand the transmission of 

infrasound - sound at frequencies lower than human hearing - to distances of several 

hundreds to thousands of kilometers; a task complicated by the fact that propagation of 

sound depends on variable winds and atmospheric temperatures. de Groot-Hedlin is the 

sole-PI on a project to develop numerical methods to compute infrasound propagation 

through realistic atmospheric conditions. She is co-PI on other projects to investigate 

infrasound propagation from various sources, including natural hazards. 

Atlantis study: A recent study to make use of the dense networks in the western United 

States was an infrasound analysis of the re-entry of the space shuttle Atlantis by de 

Groot-Hedlin et al. (2008a). Space shuttles usually lands at the Kennedy Space Center in 

Florida, but severe weather in that area on June 22, 2007 forced NASA to direct Atlantis 

to the alternate landing site at Edwards Air Force Base in the Mojave Desert in southern 

California. On its approach, the shuttle passed just west of Baja California and then 

across San Diego and Los Angeles before passing below the sound barrier over the 

Mojave Desert. The sonic boom was heard by millions of people and the infrasound 

generated by the shuttle was examined at over three hundred three-component seismic 

stations in the USArray, various regional seismic networks and three infrasound stations 

in southern California and western Nevada. The temporary presence of the transportable 

USArray in this region provided this study with a much broader and denser array of 

sensors than would otherwise be available. A GPS receiver onboard the space shuttle 

recorded the shuttle's position and time along its trajectory, yielding a rare opportunity to 

evaluate present-day atmospheric models over a dense network using infrasound signals 

for a source with a known time and location. 

Over one hundred seismic sensors and all three infrasound stations recorded the 

signal. For comparison, travel times were predicted using rays propagated through 

atmospheric specifications provided by a wind and temperature model provided by the 

Naval Research Labs. Observed arrival times are compared to predicted arrival times in 

the figure below. Comparison of predicted versus observed travel times shows agreement 

over much of the study area. To the east of the shuttle trajectory, there were no detections 

beyond the primary acoustic carpet, but infrasound energy was detected hundreds of 

kilometers to the west and northwest of the shuttle trajectory, consistent with the 

predictions of ducting due to the westward summer-time stratospheric jet. To the 

northwest, regions of ensonification are predicted to alternate with shadow zones. 

However, infrasound energy was detected to up to twenty kilometers within predicted 

shadow regions.

Figure caption a) Map of stations used in the study by 

de Groot-Hedlin et al. (2008a). Filled circles indicate 

seismic and infrasound stations that recorded an arrival, 

color-coded according to observed first arrival time, in 

seconds after 1900 GMT. For comparison, the shuttle 

speed drops below Mach 1 at 2732 s after 1900 GMT. 

The supersonic portion of the shuttle trajectory is 

shown in red. Empty circles indicate station locations 

where signal were not detected. b) Map of ray 

endpoints that reach the ground, for rays starting along 

the supersonic portion of the shuttle trajectory. Only 

stratospheric and tropospheric arrivals were considered. 

The endpoints are color-coded according to the 

predicted arrival time. Empty circles mark stations 

where signals were not observed. Filled circles indicate 

stations where arrivals were detected. 

Hydroacoustics: Catherine de Groot-Hedlin is co-PI 

with Donna Blackman on an investigation of the 

propagation of hydroacoustic energy through the 

Antarctic Convergence Zone (ACZ), the site of a sharp discontinuity in acoustic velocity. 

Propagation of hydroacoustic energy through this region is of interest for the purpose of 

developing a worldwide nuclear test-ban monitoring system. 

A research cruise was conducted in December 2006, along a transit from 

Christchurch, New Zealand to McMurdo station in the Antarctic. A number of explosive 

charges with sizes from 2 to 12 lb were fired at depths from 300m to 600m. These shots 

were recorded at several hydroacoustic stations that form a part of the International 

Monitoring System (IMS) at distances of 5000 to 9000km from the source. Our results 

show that changes is the signal duration and average sound velocity from shots in the 

ACZ varies with latitude. 


de Groot-Hedlin, C.D., M.A.H. Hedlin, K.T. Walker, D. D. Drob, and M.A. Zumberge, 

Evaluation of infrasound signals from the shuttle Atlantis using a large seismic 

network, J. Acoust. Soc. Am., 124, 1442-1451, (2008a) 

de Groot-Hedlin, C.D., Finite-difference synthesis of infrasound propagation through an 

absorbing atmosphere, J. Acoust. Soc. Am., 124, 1430-1441, (2008b) 

de Groot-Hedlin, C.D., D.K. Blackman, and C.S. Jenkins. Effects of variability 

associated with the Antarctic Circumpolar Current on sound propagation in the ocean, 

29th Monitoring Research Review, 30, Portsmouth, Virginia, (2008c) 

Herrin, E.T., Bass, H.E., B. Andre, R.L. Woodward, D. D. Drob, M.A.H. Hedlin, M.A. 

Garces, P.W. Golden, D.E. Norris, C.D. de Groot-Hedlin, K.T. Walker, C.A. L. 

Szurbela, R.W. Whitaker, and F.D. Shields, High-altitude infrasound calibration 

experiments, Acoustics Today, 4, 9-21, (2008)

LeRoy M Dorman 


Email address: ldorman@ucsd.edu 


Research Interests: Structure and evolution of the seafloor and its margins, instrumentation to 

study those things. Seismology, especially of shallow structure. 

My recent work concerns episodic tremor and slip (ETS), a relatively recent field of 

interest in seismology and hydrogeology. During the CRSEIZE experiment, we (Brown and 

others, 2005) observed correlations between fluid flow through the seafloor, seismic noise, and 

seismicity. These correlations were observed on flowmeter-equipped OBSs sited near an outof-sequence 

thrust in the Middle America Trench off Costa Rica. 

Fluid flow modeling by Alison LaBonte in her thesis supports the assertion that these 

fluid flow anomalies are due to aseismic creep occurring beneath the OBS/flowmeters. 

The noise accompanying the flow anomalies is distinctive in its statistics, possibly 

allowing the use of seismic data alone to detect these creep events. Common seismic noise is 

normal (Gaussian) in its statistics, meaning that information at different temporal frequencies 

is independent. This is not so for the flow-correlated noise, which shows coherence between 

different frequencies. 

For the usual seismic background noise, this calculation would produce zeros except 

on the main diagonal. The off-diagonal bands shown above are not present.

Why should anyone care? Countries (like Japan) which are at risk from subduction 

zone earthquakes and have offshore seismic monitoring systems may able to use these statistics 

to detect and map aseismic creep using seismic noise data. 


Dorman, L.M. and A.W Sauter, 2006, A reusable implosive seismic source for midwater or 

seafloor use, Geophysics, 71, Q19-Q24. [PDF] 

DeShon, H.R., Schwartz, S.Y., Newman, A.V., Gonzalez, V., Protti, M., Dorman, L.M., Dixon, 

T., Norabuena, E., and E. Flüh, 2006, Seisomgenic zone structure along the Middle America 

Trench, Nicoya Peninsula, Costa Rica, from 3D local earthquake tomography using P- and Swave 

data, Geophys. J. Inter., 164, 109-124, January 2006 doi:10.1111/j.1365- 

246X.2005.02809. .[PDF] 

Brown, K.M., Tryon, M., DeShon, H.R., Dorman, L.M. and S.Y. Schwartz, 2005, Correlated 

transient fluid pulsing and seismic tremor in the Costa Rica subduction zone, Earth Planet. 

Sci. Lett., 238, 189-203, doi:10.1016/j.epsl.2005.06.0055. [PDF]

Neal Driscoll 

Professor of Geology 

Email address: ndriscoll@ucsd.edu 


Research Interests: Landscape and seascape evolution in response to tectonic deformation, sea-level 

fluctuations, and climate; neotectonics and geohazards. 

During the past year, our group has been examining landscape and seascape evolution in a number of 

tectonically active areas to determine how tectonic deformation, sea level fluctuations, and climate affect 

margin development and evolution. For brevity, I will highlight some of our ongoing research on tectonic 

deformation offshore La Jolla as well as our work on sea cliff erosion and sand supply in the southern 

Oceanside Littoral Cell. 

Subsurface seismic and swath bathymetry data recently acquired offshore La Jolla, California provide an 

unprecedented three-dimensional view of the La Jolla and Scripps submarine canyons and the tectonic 

deformation in the region (Figure 1). Tectonic uplift and subsidence associated with constraining and 

releasing bends along the right lateral Rose Canyon fault system imparts a shore-parallel pattern of 

deformation that controls nearshore sediment accumulation. 

Figure 1. New bathymetry map for the San Diego region 

showing the La Jolla Canyon and the structural high 

(pop-up structure) associated with the left-lateral 

constraining bend on the Rose Canyon Fault 

(http://pubs.usgs.gov/sim/2007/2959/). 

Seismic profiles reveal that the nearshore sand thickness 

thins to zero above the uplifted bedrock near Penasquitos 

Lagoon, while the thickest sands occur to the south of the 

pop-up structure and between the Scripps and La Jolla 

Canyon. The observed sediment thicknesses suggest that 

tectonic deformation and sea level control long-term 

sediment accumulation in the region, and hydrodynamics 

control sediment dispersion. These new insights have 

improved or understanding of offshore sand resources and 

exposure of hardgrounds in the southern California 

Borderlands. 

Beaches in San Diego County are an important natural 

resource. Economic studies reveal that beach related 

tourism and associated services contribute more than $200 

million a year to the local economy. However, there is growing concern that this resource is at risk. The 

damming of local rivers, urbanization, and armoring of the bluffs are reducing the natural sand supply to 

the beach. This reduction in sand supply, along with the documented seal-level rise (2-3 mm/yr), is 

forcing local municipalities to carry out beach sand nourishment projects. At the same time, our 

understanding of the beach sand budget and the relative importance of the different sources are changing. 

Ongoing research by our group suggests that bluff erosion currently contributes more to the beach sand 

budget than previously thought. We have been conducting LIDAR (Light Detection And Ranging)

surveys of the sea cliffs in the southern Oceanside Littoral Cell to achieve a better understanding of the 

relationship between bluff erosion and beach sand supply. 

Figure 3. Repeat 

surveys allows us to 

determine how quickly 

failed material is 

reworked by wave 

erosion. Grain size data 

is also acquired to 

determine what 

percentage of the 

failure may remain on 

the beach. Note ~90 

cubic meters of material 

was eroded during a 

two-week period in June 

2007. 


Figure 2. Multiple LIDAR scans 

along Torrey Pines have been 

conducted since 2006. In addition to 

establishing a baseline from which 

future erosion can be assessed, we are 

surveying numerous failures to 

determine how fast they are reworked 

by wave erosion. Dark semicircles 

denote scanner locations and are 40 

m apart for scale. 

Dartnell, P. Normark, W.R., Driscoll, N.W., Babcock, J., Gardner, J.V., Kvitek, R.G., and P.J. Iampietro, 2007, 

Multibeam Bathymetry and Selected Perspective Views Offshore San Diego, California. USGS Scientific 

Investigations Map 2958, Sheets 1 & 2. 

Hill, J.C. and N.W. Driscoll, 2008, Paleodrainage on the Chukchi Shelf reveals sea level history and meltwater 

discharge. Marine Geology, 254:129-151; doi: 10.1016/j.margeo.2008.05.018. 

Hill, J.C., Gayes, P.T., Driscoll, N.W., Johnstone, E.A., and G.R. Sedberry, 2008, Iceberg scours along the southern 

U.S. Atlantic margin. Geology, 36: 447-450; doi: 10.1130/G24651A.1. 

Hogarth, L.J., Babcock, J., Driscoll, N.W., Le Dantec, N., Haas, J.K., Inman, D.L., and P.M. Masters, 2007, Longterm 

tectonic control on Holocene shelf sedimentation offshore La Jolla, California. Geology, 35, 3: 275–278 

doi: 10.1130/G23234A.1. 

Newman, K.R., Cormier, M., Weissel, J.K., Driscoll, N.W., Kastner, M., Solomon, E.A., Robinson, G., Hill, J.C., 

Singh , H., Camilli , R., and R. Eustice, 2007, Active methane venting observed at giant pockmarks along the 

mid-Atlantic shelf break. Earth and Planetary Science Letters, 267:341-352 doi:10.1016/j.epsl.2007.11.053. 

Slingerland, R., Driscoll, N.W., Milliman, J. D., Miller, S., and E. Johnstone, 2008, Anatomy and Growth of a 

Holocene Clinothem in the Gulf of Papua, J. Geophys. Res., 113: F01S13; doi:10.1029/2006JF000628. 

Van Wijk, J.W., Lawerence, J.F., and N.W. Driscoll, 2008, Formation of the Tranantarctic Mountains related to 

extension of the West Antarctic Rift. Tectonophysics, 10:117-126; doi:10.1016/j.tecto.2008.03.009.

Matthew Dzieciuch 


Email: mad@ucsd.edu 

Phone: 4-7986 

Research interests: ocean acoustic tomography, signal processing 

Philippine Sea Experiment 

Over the past year I have been partipating in the planning for a new ocean acoustic 

tomography experiment. The experiment has been funded by the Office of Naval Research 

and will take place in the Philippine Sea starting in 2009 and ending in 2011. The experiment 

takes place in a challenging and dynamic part of the ocean, which is located near, but not in 

the origin of a major western boundary current, the Kuroshio. The location of the acoustic 

array is shown in the figure. The program has two main goals, one is oceanographic in 

nature, and the second explores acoustic issues. 

Figure 1: Plan view of the experimental configuretion. The black dots show locations of 

moorings and the lines show acoustic paths between them.

It has been speculated and results from recent modeling work (see the first paper 

referenced below) confirm that ocean basin western boundary currents radiate barotropic 

waves that carry a large amount of energy with them. These are difficult to detect with standard 

oceanographic instrumentation but should be possible to detect with a tomographic 

array like the one that we have designed. A secondary purpose is to find the limits of ocean 

model predictability given the strong constraints of the tomography data and thus improve 

model performance. 

The second goal is to continue to explore the limits of ocean acoustic systems whose 

time and space coherence scales are limited by the ocean’s dynamics. Since this experimental 

location is in a much more energetic location than previous ones in the North Pacific, it 

will be interesting to see how stable the acoustic paths are in this area. Differences in 

stratification, and increased mesoscale energy, are expected to strongly influence the results. 

Finally, the experiment is has a interesting technology challenge. One of the moorings 

will include more than 100 internally-recording autonomous hydrophones on a vertical 

line array. The independent units will run for one year on a single DD-cell battery and be 

capable of recording 16 Gbytes of acoustic data. This is made possible by the continued 

miniaturization of modern electronics. 

Recent publications: 

Miller, A.J., Neilsen, D.J., Luther, D.S., Hendershott, M.C., Cornuelle, B.D., Worcester, 

P.F., Dzieciuch, M.A., Dushaw, B.D., Howe, B.M., Levin, J.C., Arango, H.G., 

and Haidvogel, D.B., Barotropic Rossby wave radiation from a model Gulf Stream, 

Geophysical Research Letters, 34 (23), [DOI 10.1029/2007GL031937], (2007). 

Dzieciuch, M., W. Munk, and D. Rudnick, Propagation of sound through a spicy ocean, 

the SOFAR overture, J. Acoust. Soc. Am., 116, 1447-1462, (2004). 

Dzieciuch, M., P. Worcester, and W. Munk, Turning point filters: Analysis of sound 

propagation on a gyre-scale, J. Acoust. Soc. Am., 110, 135-149, (2001).

Yuri Fialko 

Associate Professor 

Email: yfialko@ucsd.edu 

Phone: 2-5028 

Research interests: earthquake physics, crustal deformation, space geodesy 

Yuri Fialko’s research is focused on understanding the mechanics of seismogenic 

faults and magma migration in the Earth’s crust, through an application of the principles 

of continuum and fracture mechanics to earthquakes and volcanic phenomena. Prof. Fialko 

is using observations from space-borne radar satellites, including the ERS and ENVISAT 

satellites of the European Space Agency, and the ALOS satellite of the Japanese Space 

Agency, as well Global Positioning System, to investigate the response of the Earth’s crust 

to seismic and magmatic loading. Figure 1 shows the results of a recent study of the 

aftermath of a large (magnitude 7.3) strike-slip earthquake that occurred in 2003 on the 

Russia-China border. Analysis of radar interferograms collected by the ENVISAT satellite 

over 3 years following the mainshock reveals lobes of line-of-sight displacements near the 

rupture trace that are indicative of a relatively shallow source. The data are best explained 

by a post-seismic slip on the earthquake rupture (either in the form of aseismic creep, 

or aftershocks), which anti-correlates with the coseismic slip (that is, afterslip is small in 

areas of high coseismic slip, and is maximum on the periphery of areas with high coseismic 

slip). The bottom panel of Figure 1 shows the best-fitting afterslip model (with red color 

representing enhanced postseismic slip, and blue color representing no slip), along with the 

predicted surface displacements. Surprisingly, the space geodetic data showed that there 

has been relatively little, if any, poroelastic deformation due to migration of pore fluids at 

depth. The data also rule out a robust viscoelastic relaxation in the lower crust. These 

findings indicate that the postseismic response following major crustal earthquakes may not 

be readily predictable, and likely involves multiple mechanisms. 

Over the recent years, there were a number of intriguing reports of “silent” slip 

events in various subduction zones around the world. These slip events appear to occur 

quasi-periodically at the bottom of the seismogenic zone, near the transition between 

the velocity-weakening part of the subduction zone interface (that remains locked in the 

interseismic period and slips primarily in great earthquakes) and the underlying velocitystrengthening 

interface (which undergoes a stable creep in the postseismic period). In 

Figure 1: Radar interferogram of 

post-seismic relaxation due to the 

M7.3 Altai (Russia) of 2003, and the 

best-fitting model. The data can be 

explained with afterslip on the earthquake 

rupture; the post-seismic slip 

on the fault is inferred to “fill in” 

the gaps left behind by the main rupture.

Figure 2: (Left) Seismic reflection profile and flow meter locations. Grey lines are inferred fault 

locations. The February time series at Site 2 is reproduced with a down-dip propagating rupture 

(best-fit model shown by a solid black arrow). The time series recorded at Site 3, 15 km along-strike 

to the northwest, is modeled with an up-dip propagating rupture on the decollement (dashed line 

and outlined arrow). (Right) Observed (dots) and modeled (solid line) fluid flow across the seafloor 

for Site 2 February time series (background flow rate removed). 

collaboration with Prof. Kevin Brown and graduate student Alison LaBonte, Prof. Fialko 

investigated anomalous transient fluid flux through the seafloor recorded near the Costa 

Rica trench during the 2000 Costa Rica Seismogenic Zone Experiment. It was hypothesized 

that the observed hydrogeologic anomalies result from a propagating slow slip at the subduction 

interface between the frontal prism and downgoing plate. Figure 2 shows a seismic 

cross-section indicating a position of the subduction interface, the instrument locations, 

and the modeled “silent rupture” (left panel), as well as the observed fluid flow through 

the seafloor, and the model prediction (right panel). By comparing the observed fluid flow 

transients to our finite element simulations, we are able to infer the probable rupture location, 

extent, propagation rate, and duration. The best-fit model suggests that the slow-slip 

event initiated within the toe at a depth of less than 4 km, and propagated bi-laterally at 

an average rate of 0.5 kilometers per day. This interpretation implies that stress in the 

shallow subduction zone is relieved episodically. Furthermore, the Costa Rica data suggest 

that episodic slow-slip events may initiate in the prism toe without being triggered by a 

seismic event further down-dip. 


Barbot, S., Y. Hamiel and Y. Fialko, Space geodetic investigation of the coseismic and 

postseismic deformation due to the 2003 M(w)7.2 Altai earthquake: Implications for 

the local lithospheric rheology J. Geophys Res., 113, B03403, 2008. 

Barbot S,, Y. Fialko and D. Sandwell, Effect of a compliant fault zone on the inferred 

earthquake slip distribution, J. Geophys Res., 113, B06404, 2008. 

LaBonte, A., K. Brown and Y. Fialko, Hydrologic detection and finite-element modeling 

of a slow-slip event in the Costa Rica prism toe, J. Geophys. Res., in press. 

Barbot, S., Y. Fialko and Y. Bock, Postseismic deformation due to the Mw6.0 2004 Parkfield 

earthquake: Stress-driven creep on a fault with spatially variable rate-and-state 

friction parameters, J. Geophys. Res., in press.

Helen Amanda Fricker  

Associate Profesor  

Email address: hafricker@ucsd.edu  

Phone extension: 46145  

Research  Interests:  cryosphere,  Antarctic  ice  sheet,  subglacial  lakes,  ice  shelves,  

satellite laser altimetry  

Helen Amanda Fricker’s main research focuses on the Earth's cryosphere, in  

particular  the  Antarctic  ice  sheet.  One  of  the  primary  questions  in  Antarctica  is  

whether  its mass  is  changing  due  to  climate  change.  Due  to  the  vast  size  of  the  ice  

sheet, and the long time periods over which it can change, satellite data are crucial for  

routine  monitoring,  in  particular  data  from  radar  and  laser  altimetry,  and  also  

imagery. Since the launch of NASA’s Ice, Cloud and land Elevation Satellite (ICESat) in  

January  2003  Helen  has  used  data  from  the  Geoscience  Laser  Altimeter  System  

(GLAS)  on  ICESat,  which  provides  accurate  elevation  data  for  ice  sheet  change  

detection. She has been affiliated with the ICESat Science Team since 1999 and was  

made  a  Team  Member  in  April  2006.  She  is  also  a  member  of  the  ICESat‐II  ad‐hoc  

Science Definition Team.  

Antarctic  subglacial  water:  In 2006 Helen and her colleagues discovered  

active subglacial water systems under the fast‐flowing ice streams of Antarctica using  

ICESat  data.    They  found  large  elevation  change  signals  in  repeat‐track  ICESat  data  

(up to 10m in some places) corresponding to draining and filling of subglacial lakes  

beneath  1‐2 km  of  ice.  Changing  the  basal  conditions  of  an  ice  sheet,  particularly  

beneath  fast  flowing  ice  streams  and  outlet  glaciers,  is  one  possible  mechanism  to  

increase its contribution to sea level rise, through increased ice flow rates in the ice  

streams.  The fact that water moves so rapidly in such large volumes implies that ice  

stream dynamics can change rapidly also, which affects how fast the ice flows from  

the continent.  With the current interest in Antarctic ice sheet mass balance and its  

potential impact on sea‐level rise, it is important to understand the subglacial water  

process so that it can become incorporated into models.  Since the original paper on  

this work, documented in a 5‐page Research Article in Science, Helen and her team  

have continued to monitor ice stream lakes.  Figure 1 shows the dramatic drainage  

event of Subglacial Lake Conway in 2006 (Fricker and Scambos, in review).  

Figure  1.  MODIS 

difference image for the 

period Nov 2007-Nov 2005 

over three linked lakes 

([U]SLC; [Upper] Subglacial 

Lake Conway, SLM; 

Subglacial Lake Mercer). 

ICESat tracks are shown as 

black lines and coloured 

track segments represent the 

elevation decrease over 

approximately the same 2 

year period.

Ice  shelf  grounding  zones:  Helen  also  uses  ICESat  data  to  map  the  

grounding zones of the ice shelves ‐ the dynamically‐active transition zones between  

grounded and floating ice.  Grounding zones (GZ) are important because they are the  

gateway through which ice flows off the grounded ice sheet into the ice shelves and  

ultimately to the ocean.  Monitoring the GZ is therefore an important part of ice sheet  

change detection, the primary objective of the ICESat mission.  Her analysis of data  

from repeated tracks, sampled at different phases of the ocean tide, has shown that  

ICESat can “see” the tide‐forced flexure zone between fully grounded continental ice  

and  fully  floating  ice  shelf  ice,  identifying  the  landward  and  seaward  limits  of  ice  

flexure, providing accurate GZ location and width information for each track.  Helen  

and postdoctoral researcher Kelly Brunt are using this new technique to map the GZ  

for large parts of the ice sheet (Ross Ice Shelf, Amery Ice Shelf and Filchner‐Ronne Ice  

Shelf).  This combined with surface elevation at the grounding lines will contribute to  

improved calculations of the ice sheet’s mass balance.  

Glacio‐seismology:  In 2008  Helen started a new NSF project with Jeremy  

Bassis  and  Shad  O’Neel  (both  ex‐IGPP  postdocs)  investigating  the  source  processes  

for seismic signals recorded in three different glaciological environments: the Amery  

Ice Shelf; the Ross Ice Shelf; and Columbia Glacier, Alaska.  

Publications 2007‐08  

FRICKER, H.A. and T.A. SCAMBOS (in review) Interlinked subglacial lake activity on  

lower Mercer and Whillans ice streams 2003‐2008, submitted to Journal of Glaciology  

September 4 th  2008.  

BASSIS, J.N., H. A. FRICKER, R. COLEMAN, J‐B MINSTER (2008) An investigation into  

the forces that drive ice‐shelf rift propagation on the Amery Ice Shelf, East Antarctica,  

Journal of Glaciology, 54(184), 17‐27.  

BORSA, A. A. H. A. FRICKER, B. G. BILLS, J.‐B. MINSTER, C. C. CARABAJAL, K. J. QUINN  

(2008) Topography of the salar de Uyuni, Bolivia from kinematic GPS, Geophysical  

Journal International, 172(1), 31‐40.  

BASSIS, J.N., H. A. FRICKER, R. COLEMAN, Y. BOCK, J. BEHRENS, D. DARNELL, J‐B  

MINSTER (2007) Seismicity and Deformation Associated with Ice Shelf Rift Propagation,  

Journal of Glaciology, 53(183), 523‐536.  

BORSA, A. A. J.‐B. MINSTER, B. G. BILLS, , H. A. FRICKER (2007) Modeling long‐period  

noise in kinematic GPS applications, Journal of Geodesy, 81(2), DOI 10.1007/s00190‐ 

006‐0097‐x.  

FRICKER, H.A., T. SCAMBOS., R. BINDSCHADLER, L. PADMAN (2007) An Active  

Subglacial Water System in West Antarctica Mapped from Space, Science, Research  

Article Published Online February 15, 2007 Science DOI: 10.1126/science.1136897.  

BORSA, A. A., H. A. FRICKER, B. G. BILLS, J.‐B. MINSTER, C. C. CARABAJAL, K. J. QUINN,  

Topography of the salar de Uyuni, Bolivia from kinematic GPS, Geophysical Journal  

International, accepted May 2007. 

Jeff Gee 

Professor in Residence 

Email address: jsgee@ucsd.edu 


Research Interests: application of paleomagnetic and magnetic anomaly data to crustal accretionary 

processes at mid-ocean ridges and past geomagnetic field variations; origin and significance of 

magnetic fabrics in igneous rocks. 

Magnetic studies of low angle faulting at slow-spreading ridges: At many sites along slow- and 

ultraslow-spreading ridges, lower crustal and upper mantle rocks have been exposed in the 

footwall of corrugated detachment faults (Fig. 1). A fundamental question about these oceanic 

core complexes is whether the unroofing of the deep seated rocks involves substantial tectonic 

rotation of the footwall. The magnetic remanence of drillcore samples can provide a first order 

test of the proposed rotations. In earlier work using unoriented core samples from core complexes 

near 15°N in the Atlantic, we suggested very large (up to 60-80°) rotations based on remanence 

directions that were much shallower than expected at the sites. These inferred rotations, however, 

required assumptions about the orientation of the rotation axis since the azimuthal orientation of 

the cores was unknown. With colleagues from Plymouth, U.K., and the University of Wyoming, 

we used borehole imagery to fully reorient several core pieces from a deep drillhole on the 

Atlantis Massif (30°N in Atlantic, Fig. 1). The remanence data from these oriented samples are 

systematically offset to the west (Fig. 1), providing unequivocal confirmation of 

counterclockwise rotation (by about 35°) about a ridge-parallel horizontal rotation axis. 

Figure 1: (left) Bathymetry of the Atlantis Massif. The star denotes the location of IODP Site 1309D which 

sampled ~1.4km of gabbroic material in the footwall beneath the corrugated detachment surface. (right) 

Remanence directions from (a) unoriented core pieces and (b,c) after reorientation for two types of data. 

Geomagnetic field fluctuations: Links between geomagnetic field intensity, reversal frequency 

and directional variability (secular variation or excursions) provide an important, but poorly 

understood, constraint on the temporal dynamics of the geodynamo. These relationships should 

be most pronounced and easiest to document in rocks that record the extremes of geomagnetic 

field behavior. Our ongoing study of the ~182 Ma Dufek layered intrusion in Antarctica is 

focused on characterizing one such interval with frequent reversals and postulated low field 

intensity. Samples from the lowermost ~500m exposed in the Dufek intrusion, reveal the 

presence of multiple polarity components, with many samples having two or three well-defined 

components evident in thermal demagnetization. We have been able to determine ancient field 

intensities for a significant fraction of these samples by the modified Thellier absolute intensity

method. We have also developed a method, based on thermal demagnetization of a threecomponent 

laboratory thermoremanence, that allows intensities to be estimated for all 

magnetization components (only the intensity of the highest temperature component can typically 

be determined with Thellier experiments). The Dufek intrusion preserves a record of multiple 

(minimum of 4) polarity intervals and low field intensity (average ~17 µT for a paleolatitude of 

52°S), in many cases comparable to values found during excursions or reversals, suggestive of a 

weak (perhaps fibrillating) field that differs markedly from more recent records of the 

geomagnetic field. 

Figure 2: (left) Sampling in the Dufek Intrusion, Antarctica. The thick brown unit is the Neuburg 

pyroxenite, a prominent marker horizon in the layered intrusion. (right) Magnetic inclination and intensity 

of the highest temperature magnetization component (filled=observed; open=anisotropy corrected). 


Morris, A., Gee, J.S., Pressling, N., John, B.E., MacLeod, C.J., Grimes, C.B. and R.C. Searle, 2008, 

Tectonic rotation in an oceanic core complex, Geology, in review. 

Selkin, P.A., Gee, J.S., Meurer, W.P., and S.R. Hemming, 2008, Archean paleointensities from the 2700 

Ma Stillwater Complex, MT, Geochemistry, Geophysics, Geosystems, in press. 

Gee, J.S., Cande, S.C., Kent, D.V., Partner, R. and K. Heckman, 2008, Mapping geomagnetic field 

variations with unmanned airborne vehicles, EOS, Trans. Amer. Geophys. Union, (May, 2008). 

Varga, R.J., Horst, A., Gee, J.S. and J.A. Karson, 2008, Direct evidence from anisotropy of magnetic 

susceptibility for lateral melt migration at superfast spreading centers, Geochemistry Geophysics 

Geosystems, 9 (8), 10.1029/2008GC002075. 

Garcés, M. and J.S. Gee, 2007, Paleomagnetic evidence of large footwall rotations associated with lowangle 

faults at the Mid-Atlantic Ridge, Geology, 35: 279-282. 

Gee, J.S. and D.V. Kent, 2007, Source of oceanic magnetic anomalies and the geomagnetic polarity 

timescale, in Treatise on Geophysics, v. 5, Geomagnetism, M. Kono, (ed.), Elsevier, Amsterdam, 455- 

507.

Alistair Harding 


Email: aharding@ucsd.edu 

Phone: 44301 

Research Interests: Marine seismology, mid-ocean ridges, continental rifting, tectonic hazards in California 

Multichannel seismic (MCS) data is the most efficient means of mapping the presence of an axial 

magma chamber (AMC) beneath mid-ocean ridges: the reflection from the magma lens characteristically 

appearing as a bright, continuous event on along-axis sections. Information on the internal state of 

the magma lens can be obtained by careful analysis of the amplitude and the amplitude variation with 

offset (AVO) of the reflection. If the magma chamber is melt rich and effectively liquid, it will not support 

the transmission of shear waves and there will be a rapid variation of amplitude with offset. Conversely 

if the magma chamber is semi-rigid with interlocking crystals – a mush, it will support S-waves 

and the P-wave velocity is higher, resulting in a weak AVO behavior and a reduced reflection amplitude. 

In this project we investigated two questions related to the internal state of the magma lens along 

the spreading centers of the Lau Back Arc basin. The first is to investigate whether there is a correlation 

between melt-rich zones and the location of high-temperature hydrothermal vents on the seafloor. Previous 

studies along the southern East Pacific Rise (Singh et al, 1998) and the Juan de Fuca ridge (Canales 

et al, 2006) suggest that such a correlation exists but, as yet, there is only limited data on this intriguing 

observation. The correlation might arise because the melt rich regions represent sections of the magma 

chamber that can sustain higher heat flow and thus tend to anchor the upwelling limbs of the hydrothermal 

systems. Thus state of the magma chamber may help to configure or reconfigure the hydrothermal 

circulation pattern within a ridge segment. 

The second area of investigation was prompted by the results of Collier & Sinha (1992) who estimated 

reflection coefficients for the magma chamber reflection along a short interval of the Valu Fa 

Ridge (VFR), the southernmost spreading center in the Lau Basin and the one closest to to the volcanic 

arc. For the region between ~22° 23’S & 22° 30’S, the median reflection coefficient estimated by Collier 

& Sinha was -0.35 but values went as high as -0.65. This median value is considerably higher than the 

reflection coefficient of -0.2 estimated for the basaltic crust of the northern East Pacific Rise (Vera et al, 

1992) and raises the possibility that these higher values are characteristic of the predominantly arc-like 

crust of the VFR. In particular, high reflection amplitudes could be indicative of high volatile content in 

the magma, resulting in either a reduction density or a sharp reduction in velocity due to exsolved gas in 

the melt (Collier & Sinha, 1992; Morton & Sleep, 1985). The highly vesicular nature of the rocks and 

the unusually low upper crustal velocities (Jacobs et al, 2007) are direct and indirect indicators of elevated 

volatile content in VFR magmas. However, with reflection coefficient estimates from only a limited 

geographic range it is hard to know whether the higher reflection coefficient estimates are representative 

of the VFR, or whether there are unrecognized biases in estimates from different investigators. 

To address these questions, we looked AVO patterns and reflection amplitudes in MCS data for 

two segments of the ridge, the VFR and a transition segment between 20 33’ S & 20 43’ S. This latter 

segment connects the northern and central Eastern Lau Spreading Center and marks the north-south 

transition from axial rift to axial high and the emergence of a near-continuous magma chamber reflector 

that continues south all the way to the tip of the VFR. Both segments have explored and potential hydrothermal 

vent sites (Baker et al., 2006), and the transition segment is the focus of the R2K integrated 

study site in the Lau basin, Figure 1.

Figure 1: Map 1: Map of the of Eastern the Eastern Lau Spreading Lau Spreading Center/Valu Fa Ridge Fa Ridge spreading spreading system system labeled labeled by major by 

sections major (a). sections The Central (a). The Lau Central Spreading Lau Spreading Center (CLSC) Center is labeled (CLSC) in is northeastern labeled in northeastern corner. Solid corner. black 

lines Solid mark black the spreading lines mark axes the and spreading where axes overlain and with where red, overlain denote an with axial red, magma denote chamber an axial reflection magma 

is present. chamber Yellow reflection circles is present. are the locations Yellow circles of explored are the hydrothermal locations of explored vent fields hydrothermal from Baker et vent al.(2005, fields 

2006). from Baker Black boxes et al.(2005, show 2006). the transitional Black boxes ELSC show (tELSC) the transitional and southern ELSC VFR (tELSC) (sVFR). and In southern the maps VFR of 

the 

(sVFR). 

tELSC 

In 

(b) 

the 

and 

maps 

sVFR 

of the 

(c), 

tELSC 

yellow 

(b) 

lines 

and 

mark 

sVFR 

melt 

(c), yellow 

zones, 

lines 

while 

mark 

blue 

melt 

triangles 

zones, while 

denote 

blue 

areas 

trian- 

of 

enhanced hydrothermal activity. Inset boxes show study sites. The region outlined in orange 

gles denote areas of enhanced hydrothermal activity. Inset boxes show study sites. The region out- 

highlights the study area of Collier and Sinha (1992). 

lined in orange highlights the study area of Collier and Sinha (1992).

Data Processing 

Although the basic processing sequence needed for the AVO analysis and the estimation of reflection 

coefficients is well established, we found that both needed to be enhance and improved to cope effectively 

with the rougher seafloor of the ELSC/VFR. The rougher seafloor produces higher amplitude 

scattering that disrupts the continuity of the magma chamber reflections and can completely obscure the 

converted S-wave reflection from the top of the magma chamber – the PmeltS arrival that is one of the 

diagnostics of a melt-rich magma chamber. To improve the quality of the data, we used a combination of 

DMO and F-K filtering to suppress side-scatter from the seafloor (Kent et al, 1996). Since this process is 

most effective when the streamer is in-line with the profile, we checked streamer orientation to guard 

against excessive feathering. 

Figure 3: Plots of seafloor bathymetry (a), AMC reflection (b), AMC amplitude (c), and reflection coeffi- 

Figure 3: Plots of seafloor bathymetry (a), AMC reflection (b), AMC amplitude (c), and reflection 

cient (d) along the transition segment. Gray areas indicate melt regions. In part (d) the red dashed line is 

coefficient (d) along the transition segment. Gray areas indicate melt regions. In part (d) the red 

a running mean dashed of the line individual is a running estimates, mean of the individual blue dots. estimates, The spike blue dots. in amplitude The spike in amplitude and reflection and coefficients 

correlate with a reflection region coefficients of melt in correlate one of with the a region two locales of melt in imaged one of the and two to locales a potential imaged and site to of a hydrothermal 

potential site of hydrothermal venting. 

venting. 

The typical procedure for estimating reflection coefficients from MCS data has been to use the 

relative amplitudes of magma chamber, primary and multiple seafloor reflections after appropriate corrections 

(e.g. Collier & Sinha, 1992). Amplitudes are more susceptible than AVO patterns to scattering 

noise and are also sensitive, for example, focussing/defocussing by local seafloor variations. We applied 

cluster analysis (Kauffman & Rousseeuw, 1991) based on waveform cross-correlation to group the AMC 

reflection and winnow the data, keeping only the largest clusters with the cleanest wavelets. We also 

found that the estimates of source amplitudes made from seafloor primary and multiple reflections de-

creased rapidly with seafloor roughness. So, rather than using the axial profiles themselves, we estimated 

source amplitudes from reflections in sediment ponds near the ridge axis. 

Results 

The AVO analysis of the transition segment identified two melt areas at 20° 36’ S and 20° 42’ S, 

Figure 2. While the AMC reflection amplitudes have a distinct peak at 20° 42’ S there is only a muted 

response near 20° 36’ S, Figure 3. Based on water column mapping, there are 2 potential hydrothermal 

areas within this segment, one of which corresponds to the melt region at 20° 42’ S. We see a similar 

pattern along the Valu Fa Ridge. The AVO analysis identifies 3 melt-rich regions, the largest of which at 

22° 28’ S has a high estimated reflection coefficient and corresponds to a known hydrothermal vent site, 

the Misiteli Field, Figure 1. A second melt-rich region is near but slightly north, ~1.3 km of the Si-Si 

field. 

Figure 2: Along-axis stacked sections of the transition segment (a) Full-offset stack. Gray regions are 

melt-rich regions Figure 2: determined Along-axis stacked from AVO sections analysis. of the Panels transition (b) segment and (c) (a) are Full-offset partial offset stack. stacks. Gray Both 

include data regions from are 2.3-3.5 melt-rich km regions offset. determined PmeltP stack from is AVO moved analysis. out at Panels 2700 (b) m/s, and while (c) are PmeltS partial stack is 

moved out offset at 2200 stacks. m/s. Both Red include horizontal data from lines 2.3-3.5 below km SG offset. 4524 PmeltP show the stack PmeltS is moved phase out on at 2700 (b) and it’s 

absence on m/s, (c). while Orange PmeltS triangles stack is denote moved location out at 2200 of potential m/s. Red hydrothermal horizontal lines fields below based SG on 4524 water column 

mapping show by the Baker PmeltS et al. phase (2006). 

on (b) and it’s absence on (c). Orange triangles denote location of 

potential hydrothermal fields based on water column mapping by Baker et al. (2006). 

The pattern of melt-rich versus mush regions along the transition segment and VFR mirrors the 

pattern seen along the southern EPR (Singh et al, 1998) and the Juan de Fuca ridge (Canales et al, 2006). 

About 90% of the axial magma lens corresponds to a crystal-laden sill, while the melt rich regions are 

typically 1-2 km long zones spaced at roughly 10 km intervals. In addition, there appears to be a tendency 

for melt-rich regions to correspond to areas of enhanced hydrothermal activity.

The estimated reflection coefficients for the VFR show elevated values over the interval between 

~22 23’S & 22 30’ S analyzed by Collier & Sinha (1992). This interval includes the high values associated 

with melt-rich region & the Misiteli field. Outside of this region, estimated reflection coefficients 

drop back down to levels closer to the those along the transition segment and estimated for the East Pacific 

Rise, ~0.2. Moreover, maximum coefficients are similar in the two segments, although the VFR estimates 

show more scatter, presumably due to the rougher topography. Thus it appears that the section of 

the VFR ridge studied by Collier & Sinha was somewhat anomalous and that any large-scale trends associated 

with the changing petrology or additional exsolved volatiles in the magma chamber are relatively 

muted. 

References 

Baker, E.T., Resing, J.A., Walker, S., Martinez, F., Taylor, B., Nakamura, K., 2006. Abundant hydrothermal venting 

along melt-rich and melt-free ridge segments in the Lau back-arc basin, Geophys. Res. Lett. 33, 

doi:10.1029/2005GL025283. 

Canales, J.P., Singh, S.C., Detrick, R.S., Carbotte, S.M., Harding, A., Kent, G.M., Diebold, J.B., Babcock, J., Nedimovic, 

M.R., 2006. Seismic evidence for variations in axial magma chamber properties along the southern 

Juan de Fuca Ridge, Earth Planet. Sci. Lett. 246, 353-366. 

Collier, J.S., Sinha, M.C., 1992. Seismic Mapping of a Magma Chamber beneath the Valu Fa Ridge, Lau Basin, J. 

Geophys. Res. 97, 14031-14053. 

Kaufman, L., Rousseeuw, P.J., 1990. Finding groups in data: an introduction to cluster analysis, Wiley, New York. 

Jacobs, A.M., Harding, A.J., Kent, G.M., 2007. Axial crustal structure of the Lau back- arc basin from velocity 

modeling of multichannel seismic data, Earth Planet. Sci. Lett. 259, 239-255. 

Singh, S.C., Kent, G.M., Collier, J.S., Harding, A.J., Orcutt, J.A., 1998. Melt to mush variations in crustal magma 

properties along the ridge crest at the southern East Pacific Rise, Nature, 394, 874-878. 

Vera, E.E., Mutter, J.C., Buhl, P., Orcutt, J.A., Harding, A.J., Kappus, M.E., Detrick, R.S., Brocher, T.M., 1990. 

The structure of 0-My to 0.2-My old oceanic-crust at 9°N on the East Pacific Rise from expanded spread 

profiles, J. Geophys. Res. 95, 15529-15556.

James Hawkins 

Research Professor 

Email address: jhawkins@ucsd.edu 


Research Interests: Evolution of convergent plate margins of western Pacific, and origin of 

back-arc basins such as Parece Vela Basin, Lau Basin, and Mariana Trough; Origin and 

emplacement of ophiolites on convergent plate margins; Crustal evolution, western Pacific 

Basin, and western North America 

Petrologic evolution of Palau: Initiation of subduction in intra-oceanic settings 

requires relative differences in plate thickness and density (i.e., age difference); a major 

zone of weakness separating the plates, e.g., a fracture zone; and a change in relative 

vectors of movement to cause convergence. These factors help explain the origin of the 

southern-most part of the > 2500 km long Kyushu - Palau Ridge (KPR). Palau Islands, at 

7°30' N, are the only significant emergent feature on KPR. Small islands are mainly 

uplifted Pliocene and younger reef carbonate. Large islands are mainly volcanic comprising 

rare boninite; major basalt, basaltic andesite and andesite; and minor dacite. Polymict 

breccia is abundant; sills, flows, dikes are common; pillows are rare. The same rock types, 

as well as high-Mg basalt, were dredged from the Palau Trench. Volcanism on Palau began 

in late Eocene and ended by early Miocene. Rocks are low-K primitive island arc- tholeiite 

series. None are MORB. REE and HFSE require a depleted mantle source. Zr* and Ti* 

suggest that melts interacted with OL-PX rocks of upper mantle or deep crust cumulates. 

Moderate enrichment of LILE and LREE indicate influx of “dehydration fluid.” Ce/Ce* 

and Eu/Eu* show no evidence for subducted sediments or recycling of arc-derived clastics 

yet there is no accreted sedimentary prism. This paradox may be owing to lack of arc or 

terrigenous clastics on seafloor formed in open ocean “sterile” equatorial latitudes. Plate 

reconstructions and paleomagnetic data suggest that the “arc” probably formed on the 

trace of a transform fault that has migrated northward and rotated clockwise up to 90° 

since Oligocene time. Episodes of transtension allowed upwelling of relatively fertile hot 

mantle into depleted mantle and sheared, altered, rocks of the transform. Episodes of 

transpression may have initiated subduction of seafloor having a thin cover of pelagic 

sediments (calcareous and radiolarian ooze, chert, chalk, limestone) deposited far from 

terrigenous sediment sources. The Palau “arc” is aseismic; we have no insight to depth of 

the subducted seafloor. Rocks similar to Palau series on Guam, and adjacent slopes of the 

Mariana Trench may have been part of this nascent convergence system.

David R. Hilton 

Professor of Geochemistry 

Email address: drhilton@ucsd.edu 


Research Interests: Noble gas and major volatile isotope geochemistry of subduction zones, mantle 

hotspots, groundwaters and geothermal systems. 

We continue to investigate volatile recycling at subduction zones, with further studies on the Izu- 

Bonin-Mariana (IBM) region which has been ear-marked by the MARGINS program of NSF for detailed 

multi-disciplinary study. Our latest work has targeted volatiles and, in particular, the isotopic signature of 

water from melt inclusions trapped in magmatic olivine phenocrysts in the Mariana Islands (Shaw et al., 

2008). We observed that the D/H ratio of the water varied from -12 to -55 permil, averaging -34 permil, 

(relative to seawater) indicating that fluids released from the down-going plate during subduction are 

enriched in the heavy isotope of hydrogen. Consequently, we surmise that subduction leads to the 

formation of complementary hydrous reservoirs that are D-enriched (mantle wedge) and D-depleted (slab). 

We discuss how this observation can be used to trace the presence of recycled material in plume-related 

oceanic basalts and to understand water cycling between different terrestrial reservoirs. 

Caption: Schematic diagram showing proposed model for how H isotopes in Earth's reservoirs are 

cycled through the subduction zone system (Shaw et al., 2008). 

Our studies on one of the world’s most spectacular fault systems - the North Anatolia Fault (NAF), 

Turkey has continued over the past year. We completed a regional survey of western Anatolia (Mutlu et al., 

2008) showing that the whole region is characterized by release of He and heat from recent additions of 

mantle-derived magmas to the crust. We also reported results of a geochemical monitoring program (trace 

elements and stable isotopes) of geothermal fluids along an 800-km transect of the NAF (Suer et al., 2008). 

The program consisted of 3-monthly visits to geothermal wells and hot springs located on the fault over the

period 2002-2004. We noted large variations in some parameters (Cl, tritium and Ca) at specific localities 

which appeared related to seismically-induced crustal perturbations. The gas chemistry portion of the 

monitoring program appears in De Leeuw (2007) with large changes in He and CO2 isotopes also observed at 

certain locations along the fault zone. This work is directly relevant to our on-going studies on understanding 

how mantle-derived fluids traverse the crust and interact with shallow fluids (Hilton, 2007). 

We undertook a detailed evaluation of groundwater dating (i.e. time since discharge) whereby we 

considered the relative merits of the tracers helium-4, chlorine-36 and carbon-14 as dating tools for old 

(Australian) groundwaters (Kulongoski et al., 2008). We presented a highly unusual dataset (including 

measurement of all three tracers on the same sample suite) and considered possible causes of discordant ages 

in terms of limitations associated with each tracer system. In a separate study, groundwaters from the Mojave 

Desert, California were used to estimate the flux of trace gases, CF4 and SF6, to the atmosphere (Deeds et al., 

2008). It was discovered that both gases are released to the groundwater system by weathering and that this 

natural flux can sustain the pre-industrial atmospheric abundances of both gases. 

Other developments over the past year include a major up-grade of electronics hardware on one of 

our noble gas mass spectrometers. This will allow us to expand our analytical capabilities to include 

nitrogen isotope variations in our studies of oceanic basalts. This is a timely addition given our recent 

expedition to the Central Indian Ridge where we dredged an extensive suite of lavas – both from the ridge 

axis and from the nearly Rodriguez Ridge – in order to study plume-ridge interaction and the degassing 

history of the Reunion hotspot. 

New Publications 

De Leeuw, G.A.M., 2007, The noble gas and carbon systematics of divergent, convergent and strike-slip 

plate boundaries: Examples from the Reykjanes Ridge, Central American Arc and North Anatolian Fault 

Zone. Ph.D. dissertation, UCSD/SIO, unpublished. 

Deeds, D. A., Vollmer, M.K., Kulongoski, J.T., Miller, B.R., Muhle, J., Harth, C.M., Izbicki, J.A., Hilton, 

D.R. and R.F. Weiss, 2008, Evidence for crustal degassing of CF4 and SF6 in Mojave Desert 

groundwaters. Geochim. Cosmochim. Acta, 72, 999-1013. 

Hilton, D.R., 2007, Perspectives in Geochemistry: The leaking mantle. Science, 318, 1389-1390. 

Kulongoski, J.T., Hilton, D.R., Cresswell, R.G., Hostetler, S. and G. Jacobson, 2008, Helium-4 

characteristics of groundwaters from Central Australia: Comparative chronology with chlorine-36 and 

carbon-14 dating techniques. J. Hydrology, 348, 176-194. 

Mutlu, H., Gulec, N. and D.R. Hilton, 2008, Helium-carbon relationships in geothermal fluids of western 

Anatolia, Turkey. Chem. Geol., 247, 305-321. 

Shaw, A. M., Hauri, E., Fischer, T.P., Hilton, D. R. and K. Kelley, 2008, Hydrogen isotopes in Mariana arc 

melt inclusions: implications for subduction dehydration and the deep-Earth water cycle. Earth Planet. 

Sci. Lett., 275, 138-145. 

Suer, S., Gulec, N., Mutlu, H., Hilton, D.R., Cifter, C. and M. Sayin, 2008, Geochemical monitoring of 

geothermal waters (2002-2004) along the North Anatolian Fault Zone, Turkey: spatial and temporal 

variations and relationship to seismic activity. Pure & Applied Geophys., 165, 17-43.

Michael A.H. Hedlin 


Email address: hedlin@ucsd.edu 


Research Interests: Analysis of acoustic signals from large-scale atmospheric phenomena; use of 

seismic and acoustic energy for nuclear test-ban verification. 

Infrasound: The study of subaudible sound, or infrasound, has emerged as a new frontier in 

geophysics and acoustics. We have known of infrasound since 1883 with the eruption of Krakatoa, 

as signals from that event registered on barometers around the globe. Initially a scientific curiosity, 

the field briefly rose to prominence during the 1950’s and 1960’s during the age of atmospheric 

nuclear testing. With the recent Comprehensive Test-Ban Treaty, which bans nuclear tests of all 

yields in all environments, we have seen renewed interest in infrasound. A worldwide network of 

infrasound arrays, being constructed ostensibly for nuclear monitoring, is fueling basic research 

into man-made and natural sources of infrasound, how sound propagates through our dynamic 

atmosphere and how best to detect infrasonic signals amid noise due to atmospheric circulation. 

Research at L2A: The new Laboratory for Atmospheric Acoustics (L2A) is the home of 

research in this field at IGPP. Several faculty, post-docs and PhD students work full or part time in 

L2A, supported by engineers and technicians in the lab and the field. Presently we study a broad 

suite of problems related to both natural and man-made sources. 

Volcano acoustics: We believe that to properly characterize activity within volcanoes it is 

necessary to study the entire wavefield – that is downgoing seismic and upgoing acoustic energy. 

We anticipate that infrasound will also emerge in the next few years as an important tool for 

closely monitoring volcanoes for ash releases that might threaten aircraft and might not be detected 

on other monitoring systems, such as seismic networks and satellites. Following the recent eruptive 

activity at Mount Saint Helens (MSH), our group joined forces with the Geological Survey of 

Canada to deploy two infrasound arrays near this volcano. One was located on the northern flank 

of MSH. The other was positioned ~ 240 km to the east to detect stratospherically ducted 

infrasound waves. We study faint recurring long-period infrasound signals (Figure 1) that 

sometimes occur before large eruptions. We believe these signals will shed light on the internal 

workings of this volcano. We are also studying large eruptions, including one event in which ash 

was released to above 30,000 feet. This event was aseismic but was very prominent acoustically. 

Figure 1: Seismic and infrasound signals from Mt St Helens are shown in the upper two traces. 

The two records are plotted together (bottom) after advancing the infrasound record 38 seconds to 

account for the propagation delay. The infrasound and seismic signals clearly have a common 

source within the volcano

Rocket experiments: Controlled sources (i.e. well known in terms of yield, 3-D location 

and time) can be used to study the propagation of infrasound through our turbulent atmosphere. 

Over the past few years we have collaborated with a number of other institutions across the United 

States to detonate 50-pound charges of high explosives at altitudes ranging up to 50 km. Such 

small charges detonated at high altitudes disturb a large volume of air, due to low confining 

pressure, and generate infrasound waves. We are presently modeling recordings of these 

explosions to improve our ability to locate infrasonic sources, and to study atmospheric structure. 

Miscellaneous studies: 1) Bolides: The global infrasound network will be used to collect 

statistics on large meteors entering our atmosphere. We believe that this direct measure of the 

influx of meteors will provide the raw data for developing statistics on the largest meteors – the 

ones that might devastate large regions on impact. This field is in its infancy as we are just 

building the global network. These impulsive events are also useful for studying atmospheric 

structure. We are currently analyzing signals from a large bolide that exploded above Oregon 

using infrasound recordings using arrays located within 2,000 km of the event and seismic stations 

in the USArray seismic network. 2) Ocean noise: Using data from our permanent array in the 

Anza-Borrego desert and two more arrays near San Diego we detect surf noise from along the coast 

of California. Infrasonic waves from the crashing surf propagate through the stratosphere to our 

stations up to 200 km away. We see further avenues for research in this area in that lower 

frequency signals, known as microbaroms, are known to propagate 1000’s of km and can be used 

to study ocean storms remotely, and can be used to probe atmospheric structure. 3) Mine Blasts: 

Our group is studying infrasound and seismic signals from mine blasts in Russia and the US to 

learn more about the physics of these sources and how waveform data can be used to discriminate 

these events from earthquakes and nuclear tests. 

Field operations: Our group has built two permanent infrasound arrays in the US and one 

in Africa. In recent years we have deployed infrasound arrays across the southwestern US to record 

signals from high-altitude explosions and natural phenomena. We currently operate a research 

array located near San Diego. A typical temporary array comprises 4 aneroid microbarometers 

spanning an area 100 meters across, with data recorded using 24-bit Reftek digitizers and 

telemetered in realtime to our lab in La Jolla. We use Sun workstations and a suite of Macintosh 

G4 and G5 computers. All data from the field is archived on a 1.3 TB RAID. All computers, and 

supporting peripherals such as printers, are linked via a broadband communications network. 


Arrowsmith, S.J., Drob, D.P., Hedlin, M.A.H. and Edwards, W., 2006, A joint seismic and acoustic study of 

the Washington State bolide: Observations and modeling, in review with Journal of Geophysical Research. 

v112, D09304, doi:10.1029/ 2006JD008001. 

Arrowsmith, S. & Hedlin, M.A.H., 2005, Observations of infrasound from surf in Southern California, 

Geophysical Research Letters, 32, No. 9, L09810,doi:10.1029/2005GL022761. 

Bass, H., Bhattacharyya, J., Garces, M., Hedlin, M.A.H., Olson, J. and Woodward, R., 2006, Infrasound, 

Acoustics Today, 2, 9-19. 

de Groot-Hedlin, C.D., Hedlin, M.A.H., Walker, K., Drob., D., and Zumberge, M., 2008, Study of 

propagation from the shuttle Atlantis using a large seismic network, J. Acoust. Soc. Am., in press. 

Hedlin, M.A.H. and Alcoverro, B., 2005, The use of impedance matching capillaries for reducing resonance 

in rosette spatial filters, J. Acoust. Soc. Am, 117, 1880-1888. 

Hedlin, M.A.H., 2006, Infrasonic Monitoring, 2006 Yearbook of Science and Technology, McGraw-Hill, 

163-166. 

Matoza, R.S., Hedlin, M.A.H., Garces, M.A., 2006, An infrasound array study of Mount St Helens, Journal 

of Volcanology and Geothermal Research. v160, issues 3-4, p249-262. 

Walker, K., Zumberge, M., Hedlin, M.A.H., and Shearer, P., .., 2007, Methodologies for determining 

infrasound phase velocity direction with an array of directional acoustic sensors, J. Acoust. Soc. Am., in 

press.

Glenn Ierley 


Email: grierley@ucsd.edu 

Phone: 4-5917 

Research interests: turbulence, applied mathematics 

In the past year I have been working closely with Dr. Phil Livermore, who arrived at 

Scripps last August. Our first goal was to understand the nature of a particular constraint 

on the magnetic field in the conducting core of the Earth. This constraint, due to J. B. 

Taylor in 1963 states that, in the absence of viscosity (and suitably nondimensionalized, that 

of the Earth is perhaps as small as 10 −15 ), the net zonal Lorentz force on each “geostrophic 

contour” must vanish. A “geostrophic contour” is defined as as a constant density surface 

at a given distance from the axis of rotation. For this purpose the Earth’s core is sufficiently 

uniform in density that such surfaces are cylindrical shells concentric with the rotation axis, 

complicated topologically by the presence of the solid inner core. 

This homogeneous constraint assumes the form of an integral quadratic in the magnetic 

field, which must vanish at each cylindrical radius. What we have found is that given 

certain assumptions on the form in which the field is expressed, the desired vanishing of the 

integral can be enforced identically if a certain discrete set of algebraic equations is satisfied. 

Enumerating that set is elementary if an inner core is absent, and amounts to a modest 

restriction on the class of admissible magnetic fields. With the inner core, the counting 

becomes trickier. In the end there are roughly three times the number of constraints to 

enforce but this case also proves not very demanding on the magnetic field. 

A richer constraint, whose implications we are just now beginning to explore, requires not 

only the above, which is a kinematic restriction, but a dynamical generalization, that the 

motions in the core be just such as to match the observed temporal evolution of the field 

at the core-mantle boundary, while preserving the Taylor condition. This is much harder 

to do, leading us to inhomogeneous cubic constraints, and many more of them. It remains 

to be seen what the quantitative consequences are for models of the present Earth’s field. 

An unanticipated by-product of the exploration above was the serendipitous discovery of 

a new general class of orthogonal polynomials that allow in a natural way for the accommodation 

of boundary conditions. The term “Galerkin” is used for an expansion in basis 

functions each of which satisfies one or more homogeneous boundary conditions for a problem. 

As a rule, such basis functions are not mutually orthogonal and they may or may not 

be an “efficient” basis set in the sense that one obtains high accuracy with only a modest 

number of elements. By contrast, the class that we have discovered is easily generated 

by using certain standard stable recurrence relations, turns out to be mutually orthogonal 

no matter the number and order of boundary conditions imposed, and is assured of being 

an “efficient” set. A proof of these properties and a derivation of the algorithm for their 

construction is not easy however. Although we have succeeded in proving these properties 

for a variety of cases, a completely general proof is still lacking and perhaps is not even 

possible, although there can be no doubt the propositions are true in general. It is probably 

this degree of complication that accounts for no one having spotted this very general family 

before. But, technical proof aside, the application of these polynomials in practice is fortu-

(a) 

1.5 

1 

0.5 

0 

-0.5 

-1 

-1.5 

n=5 

n=10 

n=15 

-1 -0.5 0 0.5 1 

x 

(b) 

3 

2 

1 

0 

-1 

-2 

-3 

n=5 

n=10 

n=15 

-1 -0.5 0 0.5 1 

x 

Figure 1: Plots of basis functions for n = 5, 10, 15. In (a), α = β = −1/2 and the functions 

satisfy the two-sided boundary conditions Ψn(−1) = Ψ ′ n(1) = 0; in (b), α = β = 1/2 

and the functions satisfy the one-sided boundary condition Ψ ′′ n(1) = Ψn(1) = 0. Note the 

quasi-equal-area property of the functions in (b) and the quasi-equal-ripple property in (a). 

nately elementary. Examples of these polynomials are indicated in Figure 1. The family is 

characterized by two parameters, conventionally α and β. Values of interest for these are 

normally [−1/2, 0, 1/2] although any values greater than or equal to −1/2 are allowed.

Miriam Kastner 

Professor of Earth Sciences 

Email address: mkastner@ucsd.edu 


Research Interests: Marine geochemistry with focus on: the role and fluxes of fluids in 

continental margins and ridge flanks including long-term monitoring of fluid chemistry and 

fluxes and their contribution to oceanic budgets; marine gas hydrates and implications for 

slope stability and climate change; chemical paleoceanography and oceanic minerals, utilizing 

existing proxies for paleo-seawater chemistry and establishing new minerals as proxies; 

sediment geochemistry and diagenesis with emphasis on marine authigenic minerals (i.e., 

phosphates, silicates, carbonates…). 

My research on the role of fluids and fluxes in continental margins in the past year 

focused on the Gulf of Mexico, Costa Rica trench system, Cascadia-offshore British Columbia, 

and Bengal and Andaman seas. For the first time we obtained a two year high resolution time 

series of formation fluid chemistry and fluxes across the Costa Rica trench system, providing 

evidence that fluids escape from the continental side of the trench into the ocean, transporting 

and influencing the chemical and isotopic compositions of seawater, as well as data on the 

importance of fluids in the earthquake cycle of convergent margins. Because methane and 

other hydrocarbons are among the important fluxes from continental margins into the ocean 

this research is intimately related to the gas hydrates focus. My gas hydrate research focuses on 

the hydrological controls on the distribution and abundance of methane hydrate in these 

tectonic settings, and on the associated flux of methane, a potent greenhouse gas, into the 

ocean and atmosphere, for example. The oceanic flux of methane into the atmosphere is as yet 

unknown, and our preliminary results in the Gulf of Mexico suggest that it greatly exceeds 

previously estimated fluxes. The above work was conducted in collaboration with Evan 

Solomon, a graduate student and recently a post doctoral fellow. 

It took a number of years to establish that the highly stable mineral marine barite can 

be used reliably for high-resolution chemical paleoceanographic research. This was 

accomplished with a former graduate student and post doctoral fellow A. Paytan. We showed 

that marine barite can be utilized for example, for characterizing the seawater Sr isotopes 

record, for studies of sedimentation rates, paleoproductivity, and seawater sulfate S isotopes 

over the past 65 million years. Most recently we extended the S isotopes research to 65-130 

Ma, with emphasis on the implications for the relations between the C and S cycles and the 

evolution of atmospheric oxygen. 

In addition to the new proxies for chemical paleoceanography, the geochemical record 

of marine sediments contains the most precious, however, complex, histories of the oceanic 

chemical and isotopic cycles. The complications are caused by diagenesis, therefore, 

understanding these reactions is as well essential in order to reconstruct the original records. 

The most recent research in collaboration with W. Wei, a former graduate student was on the 

oceanic cycles of the most abundant anion Cl and its stable isotopes. We showed that 

especially in subduction zones Cl does not behave as a conservative component as previously 

assumed. The Cl isotopes data indicate that Cl is involved in fluid-sediment and basement 

hydration-dehydration reactions providing insights on seawater cycling at plate boundaries.

Relevant Recent Publications 

Kastner, M., Claypool, G., and G. Robertson, 2008, Geochemical constraints on the origin of pore 

fluids and gas hydrate distribution at Atwater Valley and Keathley Canyon, Northern Gulf of 

Mexico. Special Edition on Scientific Results of 2005 Chevron JIP Drilling for Methane 

Hydrates Objectives in the Gulf of Mexico, Ruppel, C., Boswell, R., and Jones, E. Eds., 

Marine and Petroleum Geology, 25, 860-872. 

Kastner, M., Torres, M., Solomon, E., and A.J. Spivack, 2008, Marine pore fluid profiles of 

dissolved sulfate; do they reflect in situ methane fluxes? Fire in the Ice, DOE, Summer 2008: 

6-8. 

Kastner, M., Spivack, A.J., Torres, M., Solomon, E., Borole,, D.V., Robertson, G.A., and H.C. 

Das, 2008, Gas hydrates in three Indian Ocean regions, a comparative study of occurrence and 

subsurface hydrology. Proceed. 6 th Interntl. Conf. on Gas Hydrates (ICGH 2008), Vancouver, 

BC, Canada, 1-6. 

Malinvero, A. Kastner, M., Torres, M.E., and U.G. Wortmann, 2008, Gas hydrate saturation from 

pore water chlorinity and downhole logs in a transect across the northern Cascadia margin 

(Intergrated Ocean Drilling Program Expedition 311), J. Geophys. Res., 113: B08103, doi: 

10.1029/2008JB005702. 

Newman, K.R., Cormier, M-H., Weissel, J.K., Driscoll, N.W., Kastner, M., Solomon, E.A., 

Robertson, G. Hill, J.C., Singh, H. Camilli, R., and R. Eustice, 2008, Active methane venting 

observed at giant seafloor pockmarks along the U.S. mid-Atlantic shelf break. Earth Planet. 

Sci. Letters, 267: 341-352. 

Solomon, E.A., Kastner, M., Jannasch, H., Robertson, G., and Y. Weinstein, 2008, Dynamic fluid 

flow and chemical fluxes associated with a seafloor gas hydrate deposit on the northern Gulf 

of Mexico slope. Earth Planet. Sci. Letters, 270, 95-105. 

Solomon, E.A., Kastner, M., and I.R. MacDonald, 2008, Considerable methane fluxes to the 

atmosphere from hydrocarbon plumes in the Gulf of Mexico, Nature Geoscience, submitted. 

Torres, M.E., Tréhu, A.M., Cespedes, N., Kastner, M., Wortmann, U.G., Kim, J-H., Long, P., 

Malinvero, A., Pohlman, J.W., Riedel, M., and T. Collet, 2008, Methane hydrate formation in 

turbidite sediments of northern Cascadia, IODP Expedition 311, Earth Planet. Sci. Letters, 

271: 170-180. 

Wei W., Kastner, M., and A. Spivack, 2008, Reply to comment on „chlorine stable isotopes and 

halogen concentrations in convergent margins with implications for Cl isotopes cycle in the 

ocean. Earth Planet. Sci. Letters, Doi:10.1016/j.epsl.2008.07.023. 

Wei, W., Kastner, M., and A. Spivack, 2008, Chlorine stable isotopes and halogen concentrations 

in convergent margins with implications for the Cl isotopes cycle in the ocean. Earth Planet. 

Sci. Letters, 266: 90-104. 

Kastner, M., Becker, K., Davis, E.E., Fisher, A.T., Jamnasch, H.W., Solomon, E.A., and G. 

Wheat, 2006, New insights into the hydrogeology of the ocean crust through long-term 

monitoring, Oceanography, 19: 30-41. 

Paytan, A., Kastner, M., Campbell, D., and M.H. Thiemens, 2004, Seawater sulfur isotope 

fluctuations in the Cretaceous. Science, 304, 1663-1665.


Email address: gkent@ucsd.edu, phone extension: 4-7386 

Research Interests: marine seismology, extensional tectonics, paleoseismology/geohazards, midocean 

ridge processes, immersive visualization, High Sierra climate 

2008 Topic: New constraints on hydroclimatic change during the last 10,000 years in the 

High Sierra from geophysical measurements in Fallen Leaf Lake, Tahoe Basin, California 

The Sierra Nevada is the primary source of California’s and northwestern Nevada’s water resources. 

To understand the potential for severe and prolonged drought in the Sierras, it is necessary to study 

past events recorded by proxy data. Fallen Leaf Lake (FLL), California, is a unique glaciolacustrine 

environment in which several climate proxies exist to provide potential records of hydroclimatic 

change during the last ~10,000 years. Recent studies have discovered submerged and upright trees 

rooted ~ 36 m below the surface of FLL, suggesting lake levels were significantly lower during the 

past. Several trees have been radiocarbon dated at ~ 1200 AD, which is consistent with the timing 

of the Medieval Climatic Anomaly (MCA) observed at other locations in the Sierra. Furthermore, 

several studies have presented evidence for a lake-size fluctuations and a mid-Holocene dry period 

in the eastern Sierra, one of which (Pyramid Lake, Nevada) is within of the same watershed as 

FLL. We conducted field campaigns during 2006—2008 to collect high-resolution marine sidescan 

and seismic CHIRP imagery, sediment cores and ROV video footage in FLL to search for 

additional submerged trees, as well as geomorphic and sedimentary evidence for hydroclimatic 

changes. Sidescan sonar imagery provided complete coverage the lakefloor and successfully imaged 

as many as 9 upright trees, over 80 downed trees, and what appear to be many in-situ stumps. 

Sidescan and ROV data also show multiple submerged paleoshorelines along the entire circumference 

of FLL to depths > ~60 m. 

In addition, over 40 line-km of 

seismic CHIRP data and 5 piston 

cores were collected to define the 

depositional and earthquake histories 

along the West Tahoe-Dollar 

Point Fault (WTDPF), which 

passes through the southern part 

of FLL. Based on radiocarbon 

samples from cores, deposition 

of material with relatively 

high magnetic susceptibility occurred 

between 3.6 - 4.9 kyr BP, 

suggesting a change in depositional 

character during the mid- 

Holocene. CHIRP profiles have 

acoustic penetration over 50 m, 

providing a stratigraphic framework 

for the entire Holocene. 

We observe up to 50 m of lacus- 

Graham Kent (left) and Neal Driscoll collecting side-scan sonar 

and seismic CHIRP imagery on another famous California 

lake—the Salton Sea.

trine sediments above a hummocky 

basal reflector, which is inferred to 

be coarse grained Tioga-aged glacial 

material. Stratal geometry observed 

in CHIRP profiles shows a 

combination of current controlled 

(contourite drifts) and gravity driven 

deposition in the upper 20-30 

m. Below this, deposition appears 

more uniform, implying a change 

occurred in the hydrodynamic conditions 

and/or sediment flux during 

the early to mid-Holocene. Based 

on the lakefloor morphology and 

timing of the most recent earthquake 

on the WTDPF (4.1 - 4.5 kyr 

BP), the submerged, upright trees 

appear to have been preserved insitu. 

In summary, the data suggest 

dramatic changes in the shoreline 

and sedimentary processes have 

occurred during the Holocene and 

demonstrate: (1) the feasibility of 

high-resolution geophysical methods 

towards finding paleoclimate 

proxies, and (2) the potential for 

the most complete, and highest fidelity 

paleoclimate record within 

the High Sierra at Fallen Leaf Lake. 

Side-scan sonar data from Fallen Leaf Lake (Tahoe 

basin), highlighting paleoshorelines (yellow arrows), and 

one of the many upright, submerged trees (green arrow) 

that casts at shadow (10 o’clock). This shadow is from a 

submerged pine tree with a bifurcated trunk that appears 

as two separate “drop outs” in the side-scan data! Many 

other trees and trunks are also visible in this image. 

Graduate student Danny 

Brothers (left) and undergraduate 

summer intern 

Stefan Jensen (Northwestern 

University) deploy the 

side-scan sonar into the 

cobalt waters of Fallen Leaf 

Lake.

Deborah Lyman Kilb 

Associate Project Scientist 

Email address: dkilb@ucsd.edu 

Phone extension: 2-4607 

Research Interests: Crustal seismology, earthquake triggering, earthquake source physics. 

Deborah Kilb’s current research areas include crustal seismology and earthquake source physics, with 

an emphasis on understanding how one earthquake can influence another. 

Ability for Large Earthquakes to Trigger Mud Volcano Eruptions: In collaboration with Dr. 

Mellors (SDSU), and his coworkers, Kilb investigates the ability for large earthquakes to trigger mud 

volcano eruptions (Figure 1). They find the temporal correlation between earthquakes and eruptions is 

most pronounced for nearby earthquakes (within ~100 km) that produce seismic intensities of 

Mercalli 6 or greater at the location of the mud volcano (Mellors et al., 2007). 

Figure 1. Plot of distance versus magnitude for earthquake and mud volcano pairs. Small dots 

show non-triggering distance/magnitude pairs in our catalog (from each earthquake epicenter to a 

known mud volcano location that did not erupt). Open stars show Azerbaijan mud volcano 

locations that were reported to have eruptions on the same day as a large earthquake. Open circles 

indicate where there was reported increased volcanic activity after large earthquakes in 

November/December 2000. Gray stars show magnitude/distance for other reported 

earthquake/eruption triggering pairs. Approximate Mercalli earthquake intensity bounds (dashed 

lines) are also shown. Note that seismic shaking of approximately Mercalli intensity 6 represents 

an approximate lower limit for triggering and that open stars juxtapose with small dots indicating 

that the assumed distance/magnitude triggering thresholds are sufficient but not always imperative, 

suggesting mud volcano’s require a recharging time to re-accumulate pressure.

Quantifying the Remote Triggering Capabilities of Large Teleseismic Earthquakes: Kilb and 

graduate student Deborah Kane are establishing new techniques to quantify the remote triggering 

capabilities of large teleseismic earthquakes. They search the ANZA network catalog for evidence of 

remote triggering, using three statistical tests (Binomial, Wilcoxon Rank-sum, and Kolmogorov- 

Smirnov) to determine the significance of quantity and timing of earthquakes in southern California 

before and after large teleseismic events. They find minimal differences between the spectral 

amplitudes and maximum ground velocities of the local triggering and non-triggering earthquakes. 

Similar analysis of remote earthquakes shows that the related ground motion regularly exceeds that of 

local earthquakes, both at low frequencies and in maximum velocity. This evidence weakly suggests 

that triggering requires larger amplitudes at high frequencies and that a maximum ground velocity 

alone is not the primary factor in remote triggering. Our results are complex, suggesting that a 

triggering threshold, if it exists, may depend on several factors. (Kane et al., 2007). 

The Temporal Lag Between a Mainshock and the First Aftershocks: Aftershocks are often obscured 

by the large decaying amplitude of the mainshock's seismic waves (coda), making it difficult to 

identify early aftershocks. Working with IGPP’s Drs. Vernon and Martynov, Kilb examined the 

temporal lag between the mainshock and the first aftershocks in the Anza 2001, southern California, 

sequence. The results show that the size of the magnitude differential between a mainshock and its 

largest aftershock is likely dictated by a combination of factors that include the complexity of the fault 

system and the propensity for relatively large earthquakes to occur in the region (Kilb et al., 2007). 

Seismogenic, Electrically Conductive, and Fluid Zones at Plate Boundaries: Working with Dr. 

George Jiracek (SDSU) and his-coworkers, Kilb examines the seismogenic, electrically conductive, 

and fluid zones at plate boundaries in New Zealand, Himalaya, and California. The results indicate 

that there is increasing evidence that processes removed from the actual seismogenic zone, such as the 

occurrence of trapped fluidized zones in the ductile crust, may be very important in the earthquake 

nucleation process (Jiracek et al., in press 2007). 

See http://eqinfo.ucsd.edu/~dkilb/current.html for an expanded description of these research projects. 


Kane, D.L., D. Kilb, A. S. Berg & V. G. Martynov, “Quantifying the Remote Triggering Capabilities 

of Large Earthquakes Using Data From The ANZA Seismic Network Catalog (Southern California)”, 

J. Geophys. Res., 112, B11302, doi:10.1029/2006JB004714, 2007. 

Kilb, D., V. G. Martynov, & F. L. Vernon, “Aftershock Detection Thresholds as a Function of Time: 

Results from the ANZA Seismic Network following the 31 October 2001 ML 5.1 Anza, California, 

Earthquake,” Bull. Seism. Soc. Am., 97780–97792, doi: 10.1785/0120060116, 2007. 

Jiracek, G.R., V. M. Gonzalez, T. G. Caldwell, P. E. Wannamaker, & D. Kilb, “Seismogenic, 

Electrically Conductive, and Fluid Zones at Continental Plate Boundaries in New Zealand, Himalaya, 

and California-USA”, AGU Geodynamics Monograph Series 175, AGU., Washington, DC, 347-369, 

2007. 

Mellors, R., D. Kilb, A. Aliyev, A. Gasanov, & G. Yetirmishli, “Correlations Between Earthquakes 

and Large Mud Volcano Eruptions,” J. Geophys. Res., 112, B04304, doi:10.1029/2006JB004489, 

2007.

Devendra Lal 


Email address: dlal@ucsd.edu 


Research interests: Cosmic ray and nuclear physics, earth sciences and solar system/planetary 

sciences. 

During the past year, we have completed a few investigations which are summarized below. 

Research papers have been submitted this year for publication in three cases. 

A. Evidence for higher biological productivity during 140 yrs B.P. in Southern Ocean during 

higher aeolian fluxes of Fe, Mn and Zn, supporting Martin’s hypothesis (D. Lal and V. Kozarev). 

We obtained data on dissolved trace element concentrations of Fe, Mn, Zn, Al and Ti 

in surface waters during 140 kyrs B.P., basing on analyses of opaline frustules in two cores on 

either side of Antarctic Polar Front (APF), based on recent discovery that the marine biogenic 

opal incorporates (Lal et al., 2006) a large number of dissolved elements in its skeleton. 

Estimated productivity indices of bioreactive elements, Fe, Mn and Zn increase non-linearly 

with their increased natural aeolian fluxes; their fluxes are deduced from observed 

concentrations of Ti in opal. Several episodes of high Ti fluxes throughout the past 140 kyrs 

are correlated with Heinrich events. High Al concentrations in diatoms in the two cores at 

levels comparable to bioreactive Fe suggest a strong catalytic role of Al in diatom productivity. 

Our data support the iron fertilization hypotheses suggested by Martin et al. (1990) for the 

HNLC zones. A paper has been submitted to Geochim. Cosmochim. Acta. 

B. Nuclear, chemical and biological characterization of formation histories of iron stones from 

several sites in Southern California: dominant role of bacterial activity (D. Lal and 5 authors) 

Pebble-sized sandstone concretions, cemented by iron and manganese oxides (iron 

stones), are found in several sites in southern California. The iron stones exhibit appreciable 

enrichments of Mn, Zn, Mg, Ti, Fe, U and Th, and fossil bacteria. Cosmogenic 10 Be 

concentrations, in the range of 10 8 10 10 atoms/g, are an excellent indicator of precipitation 

amounts. Our data favor the model that the iron stones formed within sandy beach ridges 

during wetter climates following dry climates during which aeolian sediment was added to the 

beach ridges. Iron, Mn, Zn and other trace element-rich leachates from the dust layers nurtured 

accelerated bacterial activity in the beach ridges down to depths of a few meters, as first 

suggested by Abbott (1981). Our observations of trace-element enrichments and bacterial 

fossils underscore the fact that the iron stones are principally a product of bacterial activity. 

The extreme alternating dry/wet climatic conditions which existed in the past in southern 

California led to the formation of iron stone concretions within the ancient beach ridges; the 

time periods represented by the iron stones from the six sites presumably cover the past ~ 1 

my. 

The recent surface explorations on the surface of Mars by the rovers SPIRIT and 

OPPORTUNITY (cf. Squyres et al. 2006.), showed that similar to southern California, extreme 

climatic conditions existed on Mars in its early history. It therefore seems that studies of iron 

stones may provide useful clues to the evolution of soils on Mars in such extreme climates, and

possibly even provide criteria to evaluate whether any bacterial activity was present at that 

time. A paper has been submitted to Jour. Royal Soc. Interface. 

C. Do geomagnetic excursions force large climatic changes and D-O events: case studies of 

several excursions in the past 800 kyr B.P.? (D. Lal) 

A geomagnetic excursion lasting centuries to millennia must cause large changes in the 

Earths environment due to appreciable related changes: in the geomagnetic shield of the Earth, 

in the topology of the Earths magnetosphere, and in the radiation fluxes in the Earths 

atmosphere. The effect of changes in the incident energetic solar and galactic cosmic radiation 

flux and solar plasma are expected to substantially modify terrestrial climate. We took the 

direct approach of examining archival records of the atmospheric temperatures based on δ 18 O 

and δ 2 H records in polar ice during and following geomagnetic excursions. Fortunately, 

several excursions occurred in the past 800 kyr which allow us to examine with confidence 

related climatic changes in the N and S hemispheres. We observed that in several cases, an 

immediate effect of the excursion is an appreciable cooling followed by rapid changes in 

climate (designated as the Dansgaard Oeschger (D-O) events) during the tenure of the 

excursion. The long duration cooling events, interspersed by rapid warming episodes, cause 

global cooling of the oceans, resulting in greater vertical mixing in the oceans, and causing in 

turn appreciable decreases in the 14 C/ 12 C ratios in the atmosphere, as noted earlier in the case of 

the unique Holocene global cooling event (Lal et al., 2007) at 8.2 Kyr B.P. We are therefore 

led to the question as stated in the title of this paper. A paper has been submitted to Journal of 

Earth System Science. 

D. Continuing Research 

Research is now being continued in the following areas: 1) Development of a new 

method to determine global nutrient concentrations in the surface waters of the oceans, based 

on proxy records found in marine opal. 2) Determination of the concentrations of short-lived 

radionuclides, 14 C, 36 Cl, 26 Al and 10 Be in the solar wind by analyzing these radionuclides by 

successive etching of lunar surface materials. 3) Determination of solar activity during the past 

1000 years (including Maunder Minimum, the historical period when limited information on 

sunspot numbers and geophysical data are available, e.g. aurora), basing studies of in-situ 14 C 

in polar ice sheets, a method developed by us. 

Recent publications 

Lal, D. and C. Charles. Deconvolution of the atmospheric radiocarbon record in the last 50,000 

years. Earth and Planet. Sci. Lett. 258, 550-560, 2007. 

Lal, D. Recycling of cosmic ray produced isotopes after their removal from the atmosphere; 

special case of transport of appreciable amounts of 10 Be to polar regions by aeolian dust. Earth 

and Planet. Sci. Lett. 264, 177-187, 2007. 

Lal, D., Large, W. G. and S. G. Walker. Climatic forcing before, during and after the 8.2 Kyr. 

B.P. global cooling event. J. Earth System Sci. 116, No. 3, 171-177, 2007. 

Lal, D., Charles, C., Vacher, L., Goswami, J.N., Jull, A.J.T., McHargue, L. and R.C. Finkel, 

2006, Paleo-ocean chemistry records in marine opal: implications for fluxes of trace elements, 

cosmogenic nuclides (Be-10 and Al-16), and biological productivity. Geochimica 

Cosmochimica Acta, 70, 3275-3289, 2006.

Gabi Laske 

Associate Research Geophysicist 

Email: glaske@ucsd.edu 

Phone: 4-8774 

Research interests: seismic surface waves and global seismology; regional seismology; seismic 

recordings on the ocean floor; ocean noise; natural disasters and global change 

Gabi Laske’s main research area is the analysis of free oscillations and seismic surface 

waves and the assembly of global and regional models. 

Free oscillations, global and regional tomography: Free oscillation parameters provide 

invaluable constraints on Earth’s internal structure that remain elusive to other seismic 

techniques. The great 2004 Sumatra–Andaman earthquake and many more recent events allow 

the measurement of these parameters to unprecedented precision. Laske and colleagues 

continue to refine the free oscillation database that will define the new REM (Reference 

Earth Model). Laske’s global surface wave database has provided key upper mantle information 

in the quest to define whole mantle structure. Graduate student Christine Houser 

recently used her data to compile an improved model of mantle shear and compressional 

velocity and bulk sound speed. 

Laske has been involved in the DESERT project (Dead Sea Rift Transect) to image crustal 

and mantle structure beneath the Araba Valley south of the Dead Sea. An intriguing aspect 

of this research is to find the cause for the uplift of the Arabian Plateau east of the Dead 

Sea Transform Fault. Thermo-mechanical modeling suggests that a plume responsible for 

the Red Sea rifting could have eroded the Arabian lithosphere though Laske’s surface wave 

study does not appear to support this idea. All other seismic component of this project 

were either equivocal or inadequate to address this issue. 

The PLUME project: Laske is the lead-PI of the multi–institutional, multi–disciplinary 

Hawaiian PLUME project (Plume–Lithosphere–Undersea–Melt Experiment) to study the 

plumbing system of the Hawaiian hotspot (Figure 1). The project aims to address fundamental 

issues such as the geographical location of the plume head and conduit and whether 

or not the plume originates in the lower mantle. Before PLUME, little was known about 

the seismic structure beneath Hawaii due mainly to the fact that the nearly linear alignment 

of the Hawaiian islands does not allow seismologists to obtain complete and unbiased 

images. The PLUME project is driven by seismology and includes co-PIs from SIO (Laske, 

Orcutt), WHOI (Collins, Detrick), U. Hawaii (Wolfe), DTM (Solomon, Hauri) and Yale 

Univ. (Bercovici). The centerpiece of the project is a large broad–band OBS array which 

is augmented by a 10–station land array. Occupying a total of over 80 sites and having an 

aperture of over 1000km, this experiment is one of the largest in the world. It is one of the 

first large-scale, long-term broad–band OSB deployments. 

An initial 35–station array deployed in 2005 with small station spacing and aperture 

focussed on the island of Hawaii, where the plume head is assumed to be located. A second, 

wider 38-instrument array deployed in 2006 reached into the lower mantle and gathered 

off-swell reference data for the undisturbed Pacific Ocean. With instrument recovery rates 

of 91% and 79% the deployment phase was highly successful, especially considering that 

more than half the instruments were never deployed before. Both deployments collected 

nearly 200 earthquakes each, providing excellent azimuthal coverage. The surface wave 

analysis of the first deployment reveals a roughly 30km thick low-velocity anomaly in the 

lower lithosphere beneath the islands of Hawaii and Maui that may be manifest of the

Figure 1: Deployment plan of the two-stage 

PLUME experiment. Also shown are existing 

and planned permanent stations of the global 

seismic network. The SWELL pilot array collected 

data on differential pressure sensors between 

April 1997 and May 1998. 

Figure 2: Cross section of the 3-D shear 

velocity model from the SWELL pilot experiment. 

Velocities represent averages over a 

100 km wide corridor along the profile. Imaging 

capabilities are reduced toward the ends of 

the profile because of lack of data (e.g. the apparent 

thickening of the lithosphere east of sites 

#1 and #8). A rejuvenation of the lithosphere 

toward the island chain is clearly imaged. ”Distance 

from zero” refers to the distance from the 

northeastern end of the line marked in the map. 

165˚ W 160˚ W 155˚ W 150˚ W 

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existing permanent global st. 

planned permanent global st. 

sites of first deployment 

(Jan 05 - Jan 06) 

sites of second deployment 

(Apr 06 - Jun 07) 

joint sites 

land stations 

(Jan 05 - Jun 07) 

SHEAR VELOCITY PROFILE 

Distance from Maui 

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Distance from zero [km] 

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Vs [km/s] 

assumed plume head. Deeper imaged features suggest that the proposed plume conduit 

is not located to the southeast but to the west of Hawaii. These results are consistent 

with Laske’s earlier findings from the 97/98 SWELL pilot experiment that covered an area 

in the southwestern corner of PLUME. SWELL showed conclusively that the Hawaiian 

lithosphere has undergone a rejuvenation process though the idea of mechanical erosion 

appears inconsistent with the data (Figure 2). 


Houser, C., Masters, G., Shearer, P. and Laske, G., Shear and compressional velocity 

models of the mantle from cluster analysis of long-period waveforms, Geophysical 

Journal International, 174, 195-212, 2008. 

Laske, G., Weber, M. and the DESERT Working Group. Lithosphere Structure Across 

the Dead Sea Transform as Constrained by Rayleigh Waves Observed During the 

DESERT Experiment, Geophys. J. Int., 173, 593-610, 2008. 

Laske, G. and Widmer–Schnidrig, R., Normal Modes & Surface Wave Measurements, Treatise 

of Geophysics, vol.1, Seismology and Structure of the Earth, Ed. B. Romanowicz 

and A.M. Dziewonski, 67-125, 2007. 

Laske, G., The Hawaiian SWELL Pilot Experiment – Evidence for Lithosphere Rejuvenation 

from Ocean Bottom Surface Wave Data, GSA Special Paper 430 , doi: 

10.1130/2007.2430(11), 2007.

Guenter W. Lugmair 

Research Chemist 

E-mail: glugmair@ucsd.edu 


Alexander Shukolyukov 


E-mail: ashukolyukov@ucsd.edu 


Research Interests: Origin and evolution of the solar system - isotopic studies on extraterrestrial 

materials; extinct radionuclides; cosmochronology; nucleosynthesis; impact structures and impact 

deposits on Earth. 

The principal aim of our work is to improve our understanding of the earliest 

evolutionary period of our solar system (i.e. the first tens of millions of years). We 

continue to explore its chronology by using mostly short term chronometers (based on 

extinct radioactive nuclei), the bearing of short-lived nuclei on planetary heating and 

differentiation, and the addition of 'exotic' nuclei to solar system matter to help constrain 

models of nucleosynthesis. We have shown that the 53 Mn- 53 Cr system (T½( 53 Mn) = 3.7 Ma) is a 

powerful tool to obtain relative ages of meteorite formation and, more general, of early solar 

system processes with a time resolution of ~1 Ma or less. The use of very precise absolute Pb-Pb 

ages of the angrites LEW86010 and Angra dos Reis and the 53 Mn/ 55 Mn ratio in these meteorites 

at the time of their solidification allows us to map the relative Mn-Cr ages of other meteorites to 

an absolute time scale. In particular, we dated various classes of chondrites, achondrites, and 

unusual meteorites, determined the timing of planetary differentiation and other processes within 

early planetary bodies. 

Our main instrument in these investigations is high precision thermal ionization mass 

spectrometry. 

We continued in the last year our chronological investigations of differentiated meteorites. 

Measurements of 53 Сr excesses and Mn/Cr ratios in individual mineral phases yield isochrons 

from which crystallization ages of meteorites can be obtained [Figure 1]. Our results indicate that 

the ages of the eucrite CMS 04049 and the angrite NWA 2999 are ~4558 Ma, while the oldest 

basalts from the eucrite and angrite parent bodies are ~4564 Ma old. Thus, these two meteorites 

belong to a younger generation. The old cluster appears to be related to the primary activity on 

the angrite and eucrite parent bodies while the “young” age cluster is likely to be the result of 

collisional disruption of the primary crust. 

In order to further appraise the consistency of short-lived and long-lived isotope 

chronometers we initiated in the last year a thorough 53 Mn – 53 Cr investigation of another angrite 

NWA 4801. A very precise Pb - Pb age of this meteorite is now available and, thus, this study 

will provide an additional, even more precise marker for mapping relative 53 Mn – 53 Cr ages onto 

an absolute time scale.

Figure 1. 53 Mn- 53 Cr isotope systematics in the mineral fractions from the eucrite CMS 04049 

(filled symbols) and the angrite NWA 2999 (open symbols). ε(53) are given as the relative 

deviation from the terrestrial standard value and are expressed in ε - units (1 ε is one part in 10 4 ). 

Chr – chromite, TR – total rock, Sil – silicates. 

Another direction of our work is the use of the Cr isotopic composition as a tracer of 

extraterrestrial material on Earth. Our studies using the 53 Mn- 53 Cr isotope system during the last 

decade have shown that all meteorite classes analyzed so far have relative 53 Cr abundances that 

are clearly different from terrestrial and are characteristic for individual classes of meteorites. 

Thus, based on measurements of the Cr isotopic composition, we can unambiguously demonstrate 

an extraterrestrial component in geological samples on Earth that contain a significant proportion 

of meteoritic Cr. The Cr method was originally used to demonstrate that the Cretaceous/Tertiary 

boundary layer contains an abundant extraterrestrial component The K/T boundary sediments 

from Stevns Klint, Denmark, and Caravaca, Spain, have a Cr isotopic signature that is very 

similar to carbonaceous chondrites. The obtained results were the first isotopic evidence for the 

cosmic origin of the K/T layer and the type of the impactor. Subsequently, this method was 

successfully applied to other impact deposits and impact melt samples. In the last year we 

completed our work on a series of impact spherule samples from Late Eocene deposits. We have 

detected an extraterrestrial component and have shown that the projectiles were ordinary 

chondrite type bodies. 

Recent Relevant Publications 

Shukolyukov, A. and G.W. Lugmair, 2007, The Mn-Cr isotope systematics of bulk angrites. In 

Lunar and Planetary Science XXXVII, #1423. Lunar and Planetary Institute, Houston. 

Shukolyukov, A. and G.W. Lugmair, 2008, Mn-Cr chronology of eucrites CMS 04049 and 

angrite NWA 2999. In Lunar and Planetary Science XXXIX, #2094. Lunar and Planetary 

Institute, Houston. 

Kyte, F.T, Shukolyukov, A., Hildebrandt, Lugmair G.W., and J. Hanova, 2008, Chromiumisotopic 

data from Late Eocene spherules indicate a likely asteroid belt provenance (submitted 

to Geology) 

Koeberl, Ch., Shukolyukov, A., and G.W. Lugmair, 2007, Chromium isotopic studies of 

terrestrial impact craters: Identification of meteoritic components at Bosumtwi, Clearwater 

East, Lappajärvi, and Rochechouart. Earth and Planetary Science Letters 256, 534–546.

Todd Martz 

Assistant Professor 

Email address: trmartz@ucsd.edu 


Research Interests: Autonomous chemical sensor development, CO2 chemistry of natural 

waters, biogeochemistry. 

Interpreting sensor data 

Biogeochemical rates of production, respiration and export can be estimated directly from a 

chemical budget and it is now possible to observe these changes using autonomous chemical 

sensors. This approach allows better spatial and temporal coverage of the ocean than possible 

with ship-based incubations, bottle casts, and sediment trap deployments. A recent focus of my 

work is the analysis of depth-resolved time series of oxygen, carbon dioxide, and nitrate obtained 

from autonomous sensors (Figures 1 & 2). 

Figure 1. Time-series of oxygen for 1.5 yr in the upper 300 m observed by a 

profiling float in the South Pacific. The box represents the consumption zone 

during the production season. From December-April as a result of primary 

productivity and grazing, particulate matter exported from the surface fuels a 

seasonal depletion of oxygen between 50-200m. Integrating the rates of 

oxygen change over depth and time gives an estimate of export production 

(Martz et al., 2008). 

Sensor Development 

My group is currently working on new chemical sensing technologies for autonomous 

applications. The first major effort in my laboratory involves adapting a commercially available 

Ion Sensitive Field Effect Transistor (ISFET) for seawater pH measurement. This work will 

occur in collaboration with Ken Johnson at MBARI. I will also work with Andrew Dickson to 

develop calibration protocols for the pH sensors. We hope to deploy the first prototypes on 

surface moorings in 2009. Ultimately, we plan to integrate these sensors into profiling floats.

depth 

depth 

10 

20 

30 

10 

20 

30 

a 

b 

170 180 190 200 210 220 230 

yearday (2004) 


POC (mmol C m -3 ) 

DIC (µmol kg -1 ) 

30 

20 

10 

2100 

2080 

2060 

2040 

Figure 2. Particulate Organic 

Carbon, POC (estimated from 

calibrated beam attenuation and 

particulate backscatter sensors) 

and dissolved inorganic carbon, 

DIC (estimated from pCO2 and 

CTD sensors) during the Labrador 

Sea spring bloom. The transfer of 

carbon from the inorganic to 

organic pool is evident in the 

upper 30m (Martz et al. (in 

review); Strutton et al. (in 

review). 

Martz, T.R, Johnson, K.S., Riser, S.C. 2008. Ocean metabolism observed with oxygen sensors on 

profiling floats in the South Pacific. Limnology and Oceanography Special Issue on 

Autonomous and Lagrangian Platforms and Sensors (ALPS), Vol. 53 (5, part 2), 2094-2111. 

Martz, T. R., DeGrandpre, M. D., Strutton, P., McGillis, W., Drennan, W. Sea surface pCO2 and 

carbon export during the Labrador Sea spring-summer bloom: an in situ mass balance 

approach (in review). 

Strutton, P, Martz, T. R., DeGrandpre, M. D., McGillis W., Drennan, W. Bio-optical 

observations in the Labrador Sea during the summer phytoplankton bloom (in review).

Guy Masters 


Email: gmasters@ucsd.edu 

Phone: 44122 

Research interests: Global seismic tomography using free oscillations, surface waves and body waves; 

interfacing seismology and mineral physics. 

In 2008, Guy Masters has continued to focus on improving global 3D models of the Earth using 

seismic tomography. We have paid particular emphasis to developing fast interactive techniques for measuring 

arrival times of long-period body waves using a cross-correlation/cluster analysis technique. The technique 

is described in Houser et al (2008a) along with new 3D whole-mantle models of P and S velocity built from 

our greatly enhanced data sets. Graduate student Urska Manners has adapted the technique to measure large 

data sets of travel times of core-diffracted waves to elucidate the nature and structure of the D" (core-mantle 

boundary) region. The addition of diffracted phases greatly improves sampling, particularly in the southern 

hemisphere and has allowed us to better define the "superplume" structures in the deep mantle. These new 

data sets have been jointly inverted with existing data sets to give improved models of deep mantle structure 

using both ray theory and finite frequency kernels (Manners and Masters, 2008a, Manners et al, 2008). 

One of the more intriguing aspects of these models is the anticorrelation of bulk sound speed 

anomalies to shear velocity anomalies seen in the superplume structures beneath Africa and the central 

Pacific. Almost all models show this feature in the D" region but there is little agreement on how high above 

the CMB (core-mantle boundary) it extends. It is important to nail this down since, if the anticorrelation 

is confined to the lowermost mantle, it could be related to the recently discovered post-perovskite phase 

transformation. However, if it extends signfiicantly above the CMB, we must invoke compositional variations 

to explain the signal. We have found that the variability among current bulk-sound speed models is largely 

explained by differences in how various researchers handle the signal from earthquake mislocation. This 

aspect is studied in Manners and Masters (2008c) where we determine which methods can give unbiased 

answers. Our best models now have the anticorrelation extending several hundred kilometers and the CMB, 

suggesting this must be a chemical effect rather than a result of the phase transformation. Finally, we note 

that Manners and Masters (2008b) introduce a novel technique to construct bulk-sound speed travel time 

residuals directly from S and P travel time residuals for the same source-receiver pairs. These bulk sound 

speed residuals also imply that the anticorrelation of bulk sound speed and shear velocity extends well above 

the CMB. 

During the last year, Masters has extended the cross-correlation/cluster analysis technique to work 

with surface wave envelope functions – essentially measuring relative group arrival times. The technique 

has allowed us to measure 300,000 relative arrival times for Rayleigh waves for each of several frequencies 

spanning 7.5mHz to 35mHz. The data can be very accurately represented by a group velocity map for each 

frequency which can reproduce the group arrival times very accurately. Fig 1. shows group velocity maps 

for a variety of frequencies. At the highest frequencies (top of Figure 1), the signal is primarily due to 

variations in crustal thickness and such maps can be used to improve our global crust and lithosphere models. 

A preliminary inversion reveals that our current global crustal model (CRUST 2.0) has many deficiencies and 

we can anticipate much better models in the near future. 


Houser, C., G. Masters, P.Shearer, and G.Laske., Shear and compressional models of the mantle from cluster 

analysis of long-period waveforms , Geophys. J. Int., 174, doi: 10.1111/j.1365-246X.2008.03763.x, 2008a. 

Houser, C., G. Masters, M. Flanagan, and P.Shearer, Determination and analysis of long-wavelength transition 

zone structure using SS precursors, Geophys. J. Int., 174, doi: 10.1111/j.1365-246X.2008.03879.x, 2008b. 

Gubbins, D., G. Masters and F. Nimmo, A thermochemical boundary layer at the base of Earth’s outer core

Figure 1: Group velocity maps for Rayleigh waves (perturbations in percent) at four different 

frequencies: from bottom to top, 15mHz, 20mHz, 25mHz, and 30mHz. At the lowest frequencies, slow 

anomalies can be identified in oceanic regions which disappear at higher frequencies but the most obvious 

features are associated with thick continental crust (Himalayas and Andes) and get extremely large in amplitude 

at short periods. 

and independent estimate of core heat flux, Geophys. J. Int., 174, doi: 10.1111/j.1365-246X.2008.03719.x, 

2008. 

Manners, U., and G. Masters, Analysis of core-mantle boundary structure using S and P diffracted waves, 

Geophys. J. Int., , submitted, 2008a. 

Manners, U., Q. Liu, G, Masters, and J. Tromp, Modeling the lowermost mantle using diffracted phases and 

finite frequency kernels, Geophys. J. Int., , submitted, 2008. 

Manners, U., and G. Masters, Relations between shear velocity and bulk sound speed in the lower mantle, 

Geophys. J. Int., , submitted, 2008b. 

Manners, U., and G. Masters, A comparison of methods for global teleseismic earthquake relocation, 

Bull.Seism. Soc. Am., , submitted, 2008c. 

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Stephen P. Miller 

Specialist in Marine Geophysics; Head, Geological Data Center 

Email address: spmiller@ucsd.edu 


Research Interests: digital archiving and preservation, marine geophysics, mid-ocean ridges, seafloor 

mapping, education and outreach. 

Data is the currency of 

science. Historical, recent, 

and real-time data drive 

discoveries and research on a 

global scale. Often, this data 

represents a relatively unmined 

resource. Principal 

Investigators are increasingly 

required to publish data, 

complete with contextual 

information (metadata). 

Research in the Geological 

Data Center (GDC) is 

focused on publishing data 

and derived products in webbased 

interfaces, which 

enable discovery and use. 

Figure 1. SIOExplorer captures the complete context of each expedition, preserving an authoritative 

version of all observations to meet the needs of future researchers. Examples are illustrated above, 

including seafloor maps and visualization scenes for every multibeam bathymetry sonar file, sound 

velocity profiles, and historic photographs. Other data include cruise reports, navigation, underway 

gravity and magnetics, subbottom profiler, current profiler, high resolution meteorology, as well as 

information on biological, chemical, dredged rock and sediment core samples. 

SIOExplorer (http://SIOExplorer.ucsd.edu) 

Operations have continued since 1970 to carefully archive and disseminate data from Scripps cruises. 

The SIOExplorer online digital library preserves the complete context of almost all types of data from 

more than 1000 cruises since the 1950’s, including cruise reports, navigation, underway gravity, 

magnetics and depth, temperature and current profiles, as well as multibeam swath bathymetry, maps and 

seafloor visualization files. SIOExplorer maintains five online collections: Cruises, Photo Archives, 

EarthRef Seamounts, Marine Geological Samples, and the Educator’s Collection. Public access is 

considerable, with 795,351 files (206 GB) downloaded over the last year. Public outreach has been 

provided through a number of national teacher workshops. 

Current SIOExplorer research focuses on automated methods for quality control, metadata generation, 

and publication of data. Efforts have been extended to develop a modified user interface, which includes

customized search options (beta version available at http://siox.sdsc.edu/search.php). Search results can 

be downloaded in bulk and viewed in Google Earth. 

Figure 2. Beta version of the SIOExplorer Interface. 

In addition to this interface for searching data, the GDC made the dynamic database of cruise ids 

available at http://gdc.ucsd.edu.Using this recently released search page, you can find a Scripps cruise id 

based on vessel, dates, principal investigator, ports, or scientific party. 

UNOLS Data Management Best Practices Subcommittee (http://data.unols.org/) 

As Co-Chair of the UNOLS Data Management Best Practices, I continue to identify best practices and 

make recommendations for improvements. The ad-hoc committee will report to the UNOLS Council on 

current community-wide practices in data and metadata capture when collecting data at sea. Existing data 

policies throughout the fleet have been identified, and work continues to develop methods for the 

community to meet reporting requirements. 

Site Survey Data Bank (SSDB, http://.ssdb.iodp.org) 

The GDC also operates the Site Survey Data Bank (SSDB) for the Integrated Ocean Drilling Program 

(IODP), a digital library with more than 6,000 data files that are used to support international panels as 

they review proposals for drilling. Approximately 90% of the holdings, including seismic sections and 

bathymetric map, are publicly available for research and education. 

Marine Metadata Interoperability (http://marinemetadata.org) 

The experiences of the GDC have been leveraged in the International community through the Marine 

Metadata Interoperability (MMI) Project. This collaboration has resulted in the publication of 

informative guidance material, development of controlled vocabularies, and continued involvement in a 

community of practitioners. 

The GDC functions under the Geosciences Research Division, leveraging partial institutional support 

with external awards from NSF and the Library of Congress. Further information is available at 

http://gdc.ucsd.edu

Jean-Bernard Minster 


Email address: jbminster@ucsd.edu 


Research Interests: Plate tectonics and plate deformation; Application of spacegeodetic 

techniques to study crustal dynamics; Satellite laser altimetry and 

Satellite Synthetic Aperture Radar applications to Earth studies; Earthquake 

source physics and large-scale supercomputer earthquake simulations; Earthquake 

prediction, pattern recognition; Multiscale modeling in geophysics & 

applications of IT technologies to earthquake modeling; Verification of nuclear 

Test Ban Treaties by geophysical means, seismic, imaging, ionosphere. Application 

of hyperspectral imaging to paleoseismology. Member of the ICESat science 

team since 1989. 

Hyperspectral images of paleoseismic trenches allow new approaches 

to extract paleoearthquake information from the geological record. Field 

Imaging Spectroscopy, as applied by Graduate Student Daniel Ragona, is a new 

methodology for data acquisition in the field using portable scanners. Analysis 

of such hyperspectral data in paleoseismology shows that high spatial and 

spectral resolution in the visible to short wave infrared provide a way to 

enhance subtle or even invisible stratigraphic and structural features. The use 

of neural networks and nai"ve Bayesian classifiers to automatically classify 

hyperspectral image data, yields an objective mapping of the structure of 

cores, samples and field exposures. In this way, asystem that integrates a 

hyperspectral scanner with pattern recognition algorithms can work as an 

enhanced eye and an objective classifier. This provides the geologist with 

additional information to facilitate the final description, interpretation and correlation 

of the geology in paleoseismic exposures and cores. Coupled with a 

spectral library of the materials observed in the excavation this approach 

also offers a new way to archive paleoseismological data for future analysis. 

Given the scarcity of near-source recordings for large earthquakes, 

numerical simulations play an important roll in the prediction of possible 

ground motion from future events. Simulations also give insight to physical 

processes of fault rupture that are difficult or impossible to empirically measure. 

Graduate Student Geoffrey Ely developed a novel finite difference simulation 

capability based on Support Operators. The implementation is highly 

scalable, enabling large scale, multi-processor modeling of earthquake rupture 

and wave propagation in realistic three-dimensional earth models with 

nonplanar interfaces and nonplanar ruptures. The method is used to simulate 

large (Mw7.6) earthquake scenarios along the southern San Andreas fault. 

The overall distribution of simulated peak ground velocities is consistent 

with those derived from the current empirical models, but important deviations 

associated with basin wave-guide and directivity effects have important 

consequences in terms of seismic hazard assessment (Figure 1). These 

simulations--which have been dubbed TeraShake simulations--have now been 

performed on a variety of computing platforms which involve hundreds to 

tens of thousands processors. This work is highly collaborative, involving 

scientists of the Southern California Earthquake Center in many Earth Science 

and Information Science disciplines.

Figure 1: Distribution of peak ground velocities calculated from a supercomputer 

simulation of a magnitude 7.7 earthquake on the Southern San Andreas fault. 

Note the high level of shakingg predicted in sedimentary basins of ghe Los Angeles 

area. 

The salar de Uyuni in the Bolivian Altiplano is the largest salt flat on Earth, a 

surface whose size and almost complete absence of topography make it an 

ideal reference target for satellite-based altimeters. Graduate Student 

Adrian Borsa modeled that surface using a detailed kinematic GPS survey 

of the salar collected by a team of investigators in support of the ICESat 

satellite laser altimetry mission. This revealed decimeter-amplitude topography 

on scales of 5˜50 km across the salar. The salt topography closely follows 

an equipotential surface of Earth’s gravity field. Solution transport of 

salt by surface and subsurface water is a likely mechanism for this correlation. 


Ragona, Daniel, Bernard Minster, Thomas Rockwell, and Jouni Jussila, Field imaging 

spectroscopy: A new methodology to assist the description, interpretation, and 

archiving of paleoseismological information from faulted exposures, J. Geophys. 

Res., 111, B10309-2006, doi:10.1029/2006JB004267, 2006. 

Ely, Geoffrey P. Steve M. Day and Jean-Bernard Minster, Asupport-operator method 

for viscoelastic wave modeling in 3-D heterogeneous media, Geophys. J. Int., 

doi:10.111/j.1365- 246X.2007.03633.x, 2007. 

Borsa, Adrian, Bruce G. Bills, and Jean-Bernard Minster, Modeling the topography 

of the salar de Uyuni, Bolivia, as an equipotential surface of Earth’s gravity field, 

J.Geophys. Res., In Press, 2008. 

Olsen, K. B., S. M. Day, J. B. Minster, Y. Cui, A. Chourasia, D. Okaya, P. Maechling, 

and T. Jordan, TeraShake2: Simulation of Mw7.7 earthquakes on the southern 

San Andreas fault with spontaneous rupture description, Bull. Seism. Soc. Am, 98, 

doi:10.1785/0120070148, pp. 1162 -1185, 2008.

Walter Munk 

Research Professor 

Email address: wmunk@ucsd.edu 


Research Interests: Ocean Acoustics and Physical Oceanography. 

AN INCONVENIENT SEA-TRUTH: Spread, Steepness and Skewness of Surface Slopes. In 

press in Volume 1, No 1 of Annual Reviews on Marine Science. 

I have worked on waves in the 1 mm to 1 m scales, straddling the transition from gravity to 

surface tension. These scales have received very little attention as compared to the longer 

surface waves, yet these are the scales at which momentum is transferred from atmosphere to 

ocean (wind stress). The incentive for this study came from a recent French compilation of 8 

million satellite images of sun glitter. The compilation raises more questions than it answers, 

hence the title. Significant information concerning the short waves comes (surprisingly) from 

measurements of pressure on the deep-sea bottom (the microseism problem) reported separately 

in a short paper with William Farrell, a former IGPP student. 

GLIMPSES OF OCEANOGRAPHY IN THE POSTWAR PERIOD, to be published by The 

Oceanographic Society in celebration of their 20th anniversary. The article reviews two recent 

books on the subject. My personal memories differ from the published accounts. 


1. Munk, W. (2006) From Ocean Acoustics to Acoustic Oceanography. EOS Transactions 

AGU 87: Ocean Sciences Meeting Supplement, Abstract OS51A-02. 

2. Munk, W. and D. Rudnick (2006) Penetrating the Deep Sound Channel; A Geometric 

Measure. EOS Transactions AGU 87: Ocean Sciences Meeting Supplement, Abstract 

OS52J-02. 

3. Colosi, J.A., and W. Munk (2006) Tales of the Venerable Honolulu Tide Gauge. J. Phys. 

Oceanogr., 36(6): 967-996. 

4. Munk, W. and B. Bills (2007) Tides and the climate; some speculations. J. Phys. Ocean., 

37(2): 135-147. 

5. Munk. W. (2008) An Inconvenient Sea-Truth: Spread, Steepness and Skewness of 

Surface Slopes. Annual Review of Marine Science. in press. 

6. Farrell, W.E. and W. Munk (2008) What Do Deep Sea Pressure Fluctuations Tell about 

Short Surface Waves? Geophysical Research Letters, in press. 

7. Munk, W. and D. Day (2008) Glimpses of Oceanography in the Postwar Period. 

Oceanography, in press.

Richard D. Norris 

Professor of Paleobiolgy and Paleoclimatology 

Email address: RNorris@ucsd.edu 


Research Interests: Dynamics of large-scale diversification in the history of life, Paleogene 

and Cretaceous warm climates including rapid climate change during greenhouse climates. 

The past year, my laboratory group has focused on biological evolution, ecology and climate 

change in the oceans. Evolutionary studies include work on the oceanographic mechanisms of 

extinction in pelagic organisms in the Pliocene (~3 Ma) and the patterns of evolution of species 

of planktic foraminifera (with student Pincelli Hull and post doctoral researcher, Phil Sexton). 

Ecological studies include work with graduate students Flavia Nunes and Jessica Carilli on 

living Atlantic corals, both to understand the genetic connectivity between Caribbean and 

eastern Atlantic corals and how corals have been affected by recent climate change. My studies 

of climate include work with post doctoral students Olli Friedrich and Andre Bornemann on 

the dynamics of unusually warm climates in the Cretaceous (~91 million years ago) and studies 

of extreme warm periods in the Paleogene by Sandra Kirtland and Johnnie Lyman. Two 

examples of this work are described below: 

Glaciation during the Cretaceous Super-greenhouse 

It is generally accepted that there were no large glaciers on the poles prior to the development of 

the Antarctic ice sheet about 33 million years ago which initiated the “Icehouse world”. Before 

this, the world was in a “greenhouse” state which reached the warmest temperatures of the past 

~300 million years during the “Cretaceous Thermal Maximum” about 91 million yeas ago. We 

have found that despite very warm conditions during the Cretaceous, with tropical ocean 

temperatures of 35-37°C [95-98.6°F], an ice sheet about 50-60% the size of the modern Antarctic 

ice cap existed for about 200,000 years, 91.2 million years ago. The common assumption that 

substantial ice could not have existed during past super-warm climates is apparently wrong. 

Figure 1: Geochemical studies of well preserved foraminifera [left] from Demerara Rise (western 

Atlantic) reveal the presence of a short lived glaciation at the time (~91 Ma) that the spectacular 

chalk cliffs of France [right] were forming. See Bornemann et al. 2008, Science 391:189-192.

We used geochemical data from exceptionally well-preserved marine microfossils in deep sea 

cores to infer the growth and eventual melting of large Cretaceous ice sheets. Our results are 

consistent with independent evidence for ice growth from Russia and New Jersey. If we are 

correct, it seems that even the super-warm climates of the Cretaceous Thermal Maximum were 

not warm enough to always prevent ice growth. 

Distribution of Living Mesopelagic Foraminifera in the Monterey Bay 

What kinds of weird and wonderful creatures live in the deep? My graduate student, Pincelli 

Hull, Karen Osborn (Post doctoral student with Greg Rouse) and I have been using video transect 

data taken with a submersible at the Monterey Bay Research Institute to look at the depth 

distribution and seasonal occurrence of mesopelagic foraminifera off California. We find that 

these spectacular species have consistent year-round distributions in a narrow depth range 

centered 300 m below the surface. The video data, collected monthly over 10 years by MBARI’s 

Bruce Robison, a collaborator on our study, show that foraminifera are concentrated near the top 

of the oxygen minimum zone and seem to maintain their depth habitat throughout the year. Other 

species of pelagic zooplankton have similarly precise depth distributions suggesting that they are 

using sensitive cues to locate fairly specific horizons in the ocean depths. 

Figure 2: Living mesopelagic foraminifera, Hastigerinella digitata, from the Monterey Bay. We 

suspect that the extensive spine network around the shell is used in prey capture. Note the 

extensive bubble network around the specimen [right], possibly a buoyancy control mechanism. 

Some Recent Publications 

Bornemann, A., Norris, R.D., Friedrich, O., Beckmann, B., Schouten, S., Sinninghe Damsté, J.S., Vogel, J., 

Hofmann, P., Wagner, T., 2008. Isotopic evidence for glaciation during the Cretaceous super 

greenhouse. Science 319 (189) DOI: 10.1126/science.1148777. 

Nunes, F., Fukami, H., Vollmer, S.V., Norris, R.D., Knowlton, N., 2008. Re-evaluation of the systematics 

of the endemic corals of Brazil by molecular data. Coral Reefs DOI 10.1007/s00338-007-0349-0 

Quillévéré, F., Norris, R.D., Kroon, D., Wilson, P.A., 2008. Transient ocean warming and shifts in carbon 

reservoirs during the early Danian. Earth and Planet. Science Letters 265: 600-615. 

Sexton, P., Norris, R.D., 2008. Dispersal and biogeography of marine plankton: long distance dispersal of 

the foraminifer Truncorotalia truncatulinoides. Geology. 36 (11) 899–902; doi: 10.1130/G25232A.1

John A. Orcutt 

Distinguished Professor of Geophysics 

Email address: jorcutt@ucsd.edu 

Phone Extension: 42887 IGPP; 26378 California Institute for Telecommunications & Information Technology 

(Calit2) 

OBSIP - Jeff Babcock and I operate the Scripps’ Institutional Instrument Center for the NSF Ocean Bottom 

Seismograph Instrument Pool (OBSIP; http://obsip.ucsd.edu ). The other major facility is at Woods Hole 

and Lamont Doherty Earth Observatory re-joined the OBSIP in 2007. The purpose is to serve the entire 

US marine seismology community by providing instrumentation and expertise in collecting marine seismic 

data through the standard NSF proposal process. In addition, we have built substantial numbers of identical 

instruments to initiate similar programs in the United Kingdom (National Oceanography Centre, Southampton), 

France (Institut de physique du globe de Paris [IPGP]) and Spain (Unidad Techologia Marina [UTM]). The 

instrumentation available globally is extensive. 

The current fleet comprises approximately 69 short period units and 41 long period (or broadband) instruments. 

The broadband units make use of new 250s natural period Nanometrics accelerometers for recording low 

frequency and broadband data. These instruments have been used recently in the Hawaii Plume experiment 

(see the Laske article in this report) as well as several others. During the Plume experiment Laske observed 

normal modes including 0S6 (≈1.04mHz) and others that were 

unobservable on many island stations. This was the first time 

such observations at very low frequencies have been observed by 

seafloor seismographs. 

Figure 1: Catastrophic failure of broadband 

OBS at ≈ 6km depth. 

During a summer 2007 recovery cruise at the Plume site, several 

Scripps and Woods Hole instruments were not recovered. In order 

to understand the failure modes, an expedition with Woods Hole’s 

Remotely Operated Vehicle (ROV) Jason was scheduled in October. 

Figure 1 shows one of the Scripps’ instruments in about 6 km of 

water. The glass balls used for floatation imploded and the “hard 

hats” surrounding the missing balls are crumpled. The implosion 

of the floats buckled the aluminum instrumentation pressure cases 

and, in this case, blew out the end caps and parts are strewn around the seafloor. The implosions did not always 

occur at the landing time, but in some cases months later implying an aging process in the glass that inevitably 

leads to failure under high pressure. As the numbers of seafloor instruments and the length of deployments 

have increased markedly, we find new failure modes, which require changes in engineering, construction and 

operations. 

Cyberinfrastructure – HiSeasNet ( http://hiseasnet.ucsd.edu ) is a satellite communications network 

operated by Jon Berger and myself at IGPP, which is designed to provide continuous Internet connectivity for 

oceanographic research ships and platforms. Access to the Internet is an integral part of nearly every research 

lab and office on land; extending this access to oceanographic ships – our seagoing laboratories – broadly 

impacts seagoing research activities. Scientists have been going to sea in ships now for approximately 250 

years. While the nature of ships has changed during that period of time making oceanographic research at sea 

increasingly productive, future changes in ship design will have only incremental impacts on the field. On the 

other hand, tools including the use of the global positioning system (GPS) with accuracies at sea now on the 

order of one meter or even better and the extension of the Internet to sea are highly disruptive technologies

that change the way oceanography is conducted. In May, Scripps added the 15 th ship in the US academic fleet 

to HiSeasNet comprising all the largest ships as well as the intermediate ships. The system relies upon C-Band 

and Ku-Band antennae located on the roof of UCSD’s San Diego Supercomputer Center. Real-time position 

and photographs from the R/V Roger Revelle can be viewed at http://mercali.ucsd.edu/rtapps/rtimbank. 

php?camera=SIO_Revelle_Axis2 . 

The NSF Ocean Observatories Initiative (OOI) comprises three types of interconnected observatories spanning 

global, regional and coastal scales. I am the Project Director for the cyberinfrastructure (CI) component of the 

OOI and Frank Vernon serves as Deputy Project Director. Matt Arrott, at Calit2, is the CI Program Manager. 

The functional scope of the cyberinfrastructure architecture is unusual and extensive: 

• Interactive Ocean Observing 

• Interactive Ocean Modeling & Data Assimilation 

• Computer-controlled Automated Data Product Generation 

• Discipline-Driven Semantic Organization of Data 

• Interactive Instrument Network 

• Integrated Observatory Management 

• 

User-Controlled Integration of Resources 

The data are available in near-real-time (latencies of seconds) and to anyone interested in the data streams. 

The data streams are continuous and pushed to the users placing a premium on computing methods that are 

stream-based and not file-based as has been the case for decades. Figure 2 provides an overall view of the 

cyberinfrastructure. 

SENSOR PLATFORMS PHYSICAL INTERFACE 

RESEARCH 

PLATFORMS 

FIXED 

CORE 

MOBILE 

CORE 

Marine 

User 

Cyber 

Operational Authority 

Proposed CyberPoPs 

MARINE OPERATIONS SHORE SIDE OPERATIONS OBSERVATORY OPERATIONS USER OPERATIONS 

Marine Net 

Observatory Net 

MARINE MANAGEMENT OBSERVATORY MANAGEMENT USER MANAGEMENT 

MARINE OPERATOR 

CYBER OPERATOR 

RESEARCH SCIENCE & EDUCATION TEAM 

RESEARCH ADMINISTRATOR 

Figure 2: The ocean sensors are to the left including PI-owned instruments and users of the system are to the 

right. The Marine Net can be either seafloor fiber optic cables or satellite communications. The Observatory 

Net includes a 10Gbps fiber optic backbone from the National Lambda Rail connecting UCSD to Portland, the 

University of Washington, Chicago, Boston, and McLean, VA. 

The Marine network provides communications at sea and a link to shoreside operations including oservatory 

management. Users and observatory management can use the near-real-time data for real-time analysis 

including assimilation into models. The knowledge created from the data can, in turn, be used to modify the 

marine network as needed. For example, autonomous vehicles can be directed to sample data in areas in which 

the model variance is large in order to improve model estimates in the future. In most cases, the interactions will 

necessarily be machine-to-machine to reduce delays associated with human interactions.

Robert L. Parker 

Professor of Geophysics, Emeritus 

Email: rlparker@ucsd.edu 

Phone: 42475 

Research Interests: Inv erse theory, geomagnetism, spectral analysis, electromagnetic 

induction. 

While his student Ashley Medin continued to work on the more difficult, general 

inverse problem of electromagnetic induction in two dimensions, Bob Parker 

devoted some effort to studying the very simplest 1- and 2-D systems in order to calibrate 

and validate her general numerical computer codes. In magnetotelluric (MT) 

surveys the complex function of frequency, the admittance c = E y /iωB x is measured 

at the Earth’s surface when a horizontal time-periodic magnetic field induces currents 

in the ground. In the simplest case electrical conductivity in the Earth is vertically 

stratified, that is σ = σ (z), and is terminated with a perfect conductor at the known 

depth h. The first question we ask is, What are the allowed values of c for such a 

structure, if the only other thing we know about σ (z) is that it is positive? The surprisingly 

simple answer is that c must always lie within a semicircular region in the 

complex plane, with diameter h on the real axis and the permissible zone below it, 

called the green zone. As ω increases from zero, the admittance of any bounded onedimensional 

conductivity structure traces a smooth curve inside the green zone, starting 

at c = h, and ending at c = 0; see Figure 1. 

Next consider the following minimalist inverse problem: we measure c at 

exactly one frequency; what can we say with certainty about σ (z)? A common way 

of selecting from among the infinite number of possible conductivities is to pick the 

one with the smallest L2 norm, σ with the smallest value of 

½ 

⎛ h 

|| σ || 2 = ⎜∫ 

⎝ 0 

σ (z)2 ⎞ 

dz⎟ 

. (1) 

⎠ 

This strategy, regularization, is often adopted to stabilize numerically delicate inverse 

problems with many data, but the most elementary problem appears to have escaped 

previous attention. By the classical variational method, we find the Euler-Lagrange 

differential equation for the complex electric field: 

E′′ = ⎧ iωμ0|λ| Re(E 

⎨ 

⎩ 

2 e iφ ) E, Re(λE 2 ) ≥ 0 

0, otherwise. 

where λ is a complex parameter and φ = arg λ. The norm minimizing conductivity is 

given by σ = Re(λ E 2 ) when positive, and zero otherwise. From these equations we 

can discover the solution to the 1-D inverse problem with the smallest L 2 norm that 

matches a single admittance value. The results are summarized in Figure 2 which 

Figure 1: The green zone and the locus of admittances for a uniform layer. 

(2)

Figure 2: Contours of the smallest ||σ || 2ω µ 0h 3/2 in the complex c plane. Below 

the red line σ >0 throughout; above it there is an insulating layer at the top. 

shows the value of the smallest possible norm at each allowed admittance. These 

solutions have been used as checks on the regularized 2-D numerical codes. 

For quality control of MT measurements, it has been suggested that at each 

observation site it should be possible to construct a 1-D conductivity structure compatible 

with the admittances measured at that site: points lying far from the 1-D 

response are treated with caution and may be rejected. This is known to be only 

approximately correct, but the discrepancies between the best-tting 1-D prole and a 

given set of data belonging to a 2-D structure have always been found to be tiny. 

Parker has discovered a class of 2-D systems in which the deviation can be extremely 

large: a thin conducting sheet with horizontally varying conductance τ (x) (vertically 

integrated conductivity) above an insulating layer, of thickness h lying over a perfect 

conductor. The system is excited by a horizontal magnetic eld in the y direction in 

transverse electric (TE) mode induction. In the example illustrated below 

τ (x) = τ 0(1 + a e −|x|/b 

) 

with a = 1 and b = ½h; the admittances are measured at x = 0. If the measured 

admittances are to be compatible with a 1-D prole, the trajectory of c(ω ) should 

remain inside the green zone as we discussed earlier; see Figure 1. However, for this 

2-D conducitivity model, the admittance lies outside the zone for every frequency 

except zero and innity. Different choices of a and b yield even larger violations, but 

it is not known at this time if they can be made arbitrarily large. In any case, the idea 

that all 2-D structures have approximate 1-D responses at a single station must be 

reconsidered. A paper on this work is in preparation. 

Figure 3: Admittances at x = 0 from a thin sheet conductor with conductance 

given by (3) and a = 1, b = ½h. The dimensionless frequency = ω µ 0hτ 0. 

( 3)

David T. Sandwell 


Email: dsandwell@ucsd.edu 

Phone: 47109 

Research Interests: Geodynamics, global bathymetry, crustal motion modeling 

During the 2008 academic year, Dave Sandwell's research was focused on solid Earth Geophysics 

with an emphasis on understanding the dynamics of the crust and lithosphere. Our group 

comprises three graduate students Karen Luttrell, Meng Wei, and Xiaopeng Tong as well as Post 

Doc. J.J. Becker. Our research is mostly supported by three grants; two are from the National 

Science Foundation with titles Observations and Modeling of Shallow Fault Creep Along the San 

Andreas Fault Zone and High-Resolution Gravity, Topography, and Seafloor Roughness while 

the third is from NASA to perform Geodetic Imaging and Modeling of the San Andreas Fault 

System. 

Radar Interferometry - After two years in orbit, the L-Band synthetic aperture radar 

(SAR) aboard the Japanese ALOS spacecraft is performing beautifully and is providing global 

interferometric crustal motion measurements. Dave Sandwell, Xiaopeng Tong, Rob Mellors 

(SDSU) and Yuri Fialko, are using theses data to investigate the coseismic and postseismic 

deformation associated with the major (Mw 7.9), and highly destructive, earthquake which 

occurred on May 12, 2008 in the eastern Sichuan province of China (Figure 1). We are 

developing new methods for mosaicking the numerous interferograms covering the 400 km by 

400 km zone of deformation. This involves the development of new ScanSAR interferometry 

methods and code 

Global Bathymetry - David Sandwell and Water Smith (NOAA - Silver Spring Maryland) 

continued their collaboration on retracking the raw radar altimeter waveforms from ERS-1 and 

Geosat to further improve the accuracy and resolution of the global marine gravity field 

(Sandwell and Smith, 2008). In addition they continue to advocate a new altimeter mission with a 

5-fold improvement in accuracy (Sandwell et al., 2006). J.J. Becker has designed a program for 

editing the 40-year archive of ship soundings and has used the edited data to estimate the slope of 

the ocean floor in relation to the critical slope needed to convert tidal energy into internal waves 

(Becker and Sandwell, 2007). This research helps to resolve the issue of, where and how, deepocean 

mixing occurs. 

Crustal Motion Modeling - Bridget Konter-Smith (now at the University of Texas, El 

Paso) continued her development of a semi-analytic model for the deformation of western North 

America that is consistent with the growing array of continuous GPS and InSAR measurements 

(Smith and Sandwell, 2006). This model was used to predict the crustal stress at seismogenic 

depth and at various times in the past. Karen Luttrell performed a series of GPS measurements in 

the Salton Trough area of California in order to measure the viscoelastic rebound of the 

lithosphere in response to unloading of Lake Cahuilla 300 years ago. Cyclic loading from Lake 

Cahuilla changes the stress field along the San Andreas Fault and could perhaps trigger a major 

rupture (Luttrell et al., 2007). 

More information is provided at http://topex.ucsd.edu.

Figure 1. Six swaths of 

radar interferometry from 

the ALOS L-band 

spacecraft reveal the 300km 

long zone of ground 

deformation associated 

with the M w 7.9 earthquake 

in Sichuan Province, China 

that killed more than 

70,000 people and left 

374,000 injured. One 

fringe is 11.6 cm of 

deformation in the line of 

sight direction of the 

spacecraft. Black line is 

mapped surface rupture. 

Over the next few months 

we will develop 

viscoelastic models for the 

postseismic response from 

this major rupture in order 

to understand the temporal 

evolution of the crustal 

stresses. 


Becker, J. J., D. T. Sandwell, Global estimates of seafloor slope from single-beam ship 

soundings, J. Geophys. Res., 113, C05028, doi:10.1029/2006JC003879 30 May 2008. 

Luttrell, K., D. Sandwell, B. Smith-Konter, B. Bills, and Y. Bock, Modulation of the earthquake 

cycle at the southern San Andreas fault by lake loading, J. Geophys. Res., 112, B08411, 

doi:10.1029/2006JB004752, 2007. 

Sandwell, D. T., D. Myer, R. Mellors, M. Shimada, B. Brooks, and J. Foster, Accuracy and 

resolution of ALOS interferometry: Vector deformation maps of the Father's Day Intrusion at 

Kilauea, IEEE Trans. Geosciences and Remote Sensing, in press, 2008. 

Sandwell, DT; Smith, WHF; Gille, S; Kappel, E; Jayne, S; Soofi, K; Coakley, B; Geli, L., 

Bathymetry from space: Rationale and requirements for a new, high-resolution altimetric 

mission. Comptes Rendus Geoscience. 338 (14-15) : 1049-1062, 2006. 

Sandwell, D. T., and W. H. F. Smith, Global marine gravity from retracked Geosat and ERS-1 

altimetry: Ridge segmentation versus spreading rate, J. Geophys. Res., accepted, September, 

2008. 

Smith, B., and D. T. Sandwell, A Model for the Earthquake Cycle Along the San Andreas Fault 

System for the Past 1000 Years, J. Geophys. Res., 111, B01405, 2006. 

Wei, M., D. T. Sandwell and Y. Fialko, Creep episodes on the Superstition Hills fault: A silent 

M5.0 event October 3-6, 2006, J. Geophys. Res., submitted September, 2008.

Annika Sanfilippo 

Specialist in Paleontology, RTAD 

Email address: asanfilippo@ucsd.edu 

Phone extension: 4-2049 

Research Interests: Radiolarian evolution, taxonomy and stratigraphy, magnetobiostratigraphic 

chronology and correlation of Cenozoic marine sequences, extinction and diversification associated with 

climate change. 

My primary work over the past year has been to provide age determinations based on 

radiolarians to solve stratigraphic, tectonic and structural problems. The presence of radiolarians in 

outcrops from Northern California and Peru, from bore holes offshore Uruguay, and sediments from 

equatorial Africa, the Gulf of Mexico, the Atlantic and Pacific Oceans have provided useful results for 

ongoing investigations at other universities. 

Fossil collections are the fundamental source of almost all paleontological science. My 

paleontological research and interests are intimately linked to the geological collections and their 

proper curation. As a curator for the U.S. West Coast Repository for the DSDP/ODP 

Micropaleontological References Centers I have inventoried 1200 new diatom and radiolarian slides, 

and continue to work on the MRC database. Work over the past year also includes revitalization and 

inventory of unique, retired and/or orphaned paleontological collections acquired by SIO Geological 

Collections as an important contribution to future paleontologist. 

My most current work is participation in a workshop, the first workshop like this, stimulated 

by the World Registry of Marine Species, who hopes to get a catalog of all living marine organisms by 

next year. They have poor coverage of protists and mollusks, and this workshop will hopefully 

accelerate the production of an authoritative list of radiolarian species. The Encyclopedia of Life 

(EOL) also has an interest, because they use the names of organisms to index information for inclusion 

on the EOL website. The agenda for the upcoming workshop is to try to gather as many names as we 

can, and then group together the names that refer to the same species (we call these groups because 

they include not only synonyms but mis-spellings, vernacular names and so on). A goal is to assist the 

radiolarian community with its on-line presence. One general view is that it is best to create central 

communal repositories of information where all experts are able to contribute. EOL is building some 

software called 'LifeDesk' which is designed for use by biologists. It will be released in December, but 

some components will be available for the workshop participants. Radiolarian experts will work on the 

single classification with all names using our on-line tools, with the goal of moving towards a 

consensus classification. The environment will be on-line, and experts will be able to continue to make 

contributions to this after the workshop. 


Brabb, E. E., Ristau, D., Bukry, D., McDougall, K., Almgren, A. A., Saul, L.-E., and Sanfilippo, A., 

2008. Newly discovered Paleocene and Eocene rocks near Fairfield, California, and correlation with 

rocks in Vaca Valley and the so-called Martinez Formation or Stage. USGS Open Files. Submitted 24 

June, 2008. Online: http://pubs.usgs.gov/of/2008/1228

Nigrini, C., Sanfilippo, A., and Moore, T. C., Jr., 2006. Cenozoic radiolarian biostratigraphy: A 

magnetobiostratigraphic chronology of Cenozoic sequences from ODP Sites 1218, 1219 and 1220, 

equatorial Pacific. In: Wilson, P. A., Lyle, M., and Firth, J. (eds.), Proc. ODP, Sci. Results, 199: 

College Station, TX (Ocean Drilling Program) 199 [Online] Available from World Wide Web: 

http://www-odp.tamu.edu/publications/199_SR/225/225.htm. [Cited YYYY-MM-DD] 

Moore, T. C., Jr., Backman, J., Raffi, I., Nigrini, C., Sanfilippo, A., Paelike, H., and Lyle, M., 2004. The 

Paleogene tropical Pacific: Clues to circulation, productivity and plate motion. Paleoceanography, 19, 

PA3013, doi10.1029/2003PA000998 

Sanfilippo, A., Hakyemez, A. and Tekin, U. K., 2003. Biostratigraphy of late Paleocene-Middle Eocene 

radiolarians and foraminifera from Cyprus. Micropaleontology, 49(1):47-64. 

Sanfilippo, A. and Fourtanier, E., 2003. Oligocene radiolarians and diatoms form the Great Australian 

Bight (Site 1128, ODP Leg 182). In: Feary, D. A., Hine, A. C., Malone, M. J. et al. (eds.), Proc. ODP, 

Sci. Results, 182: College Station, TX (Ocean Drilling Program). http://wwwodp.tamu.edu/publications/182_SR/004/004.htm 

Sanfilippo, A. and Blome, C. D., 2001. Biostratigraphic implications of mid-latitude Paleocene-Eocene 

radiolarian faunas from Hole 1051A, Ocean Drilling Leg 171B, Blake Nose, western North Atlantic. 

In: Kroon, D., Norris, R. D., and Klaus, A. (eds.), Western North Atlantic Paleogene and Cretaceous 

Paleoceanography. Geological Society, London, Special Publication, 183, pp. 185-224.

Glenn Sasagawa 

Associate Project Scientist 

Email address: gsasagawa@ucsd.edu 


Research Interests: Seafloor geodetic measurements. 

Glenn Sasagawa's research focuses on the design, development, and deployment 

of scientific instrumentation to investigate geodetic questions in the marine environment. 

In the 2007-2008 academic year. construction of a prototype seafloor pressure reference 

was completed. A prototype gravimeter for deployment on an Autonomous Underwater 

Vehicle (AUV) was also constructed and tested at sea. Data analysis for a continuously 

recording seafloor instrument was completed and the results were published, along with 

several other papers on seafloor gravity measurements and interpretation. The geodetic 

research is a group effort that includes Mark Zumberge. 

Seafloor Pressure Standard: Continuously recording seafloor pressure gauges have 

been used to monitor episodic vertical deformation on the seafloor. However, the 

instrument readings slowly drift in time, masking any slow signals due to seafloor deformation. 

We have built a laboratory prototype that can provide a stable pressure 

reference signal for geodetic applications. A fixed mass resting on a precisely machined 

hydraulic cylinder provides a known and stable pressure signal; standard pressure 

calibration systems use this technique. A seafloor pressure gauge would periodically 

measure, in situ, the reference pressure signal. In turn the pressure gauge drift would be 

determined and the uncontaminated slow deformation signals would be extracted. 

oil 

Piston 

Cylinder 

Single weight 

Valve #2 

Pressure 

gauge 

Valve #1 

Accumulator 

Figure 1. A schematic representation of the laboratory prototype hydraulic 

layout. The three-way valve #1 switches the pressure gauge between the piston 

gauge calibration pressure source and simulated seawater pressure simulated by 

accumulator (a bladder of oil inside a pressurized gas cylinder). The metering 

valve #2 pressurizes the piston until the weight is floated to its operating position; 

valve #2 is then closed. 

Oil

Figure 

Figure 2. The laboratory prototype. The hydraulic accumulator is the black 

cylinder in the background. The three-way and metering valves are labeled 

actuator 1 and 2, respectively. The piston gauge mass is the gray weight stack to 

the right; an optical pattern is attached for use with an optical tachometer. The 

spin-up motor assembly is mounted on the lever assembly; another motor lowers 

the spin-up motor onto the weights. The pressure gauge is kept in a blue 

insulated container in the background. 

The system was operated autonomously in a temperature-controlled laboratory for 

50 days. The calibrations were repeated every 2 hours initially, and then programmed to 

repeat every 12 hours. The nominal pressure generated by the weight is 139.305 bar. 

After correcting for the barometric pressure variation, the pressure repeatability as 

estimated by the pressure standard deviation of the values is 0.736 mbar (5.3 ppm), 

corresponding to seawater changes of 0.7 cm. 

We are now designing a follow-on system for autonomous deployment on the 

seafloor. A proposed target site is Axial Volcano on the Juan de Fuca ridge, which is an 

active area of seafloor volcanic deformation associated with eruptive cycles.

AUV Gravimetry 

Marine gravity measurements are almost always collected with gyroscopically 

stabilized instruments about surface ships. Surface measurements are, however, limited 

by physical laws to resolving seafloor features with dimensions greater than the water 

depth of the water. Surface measurements must also filter out the acceleration noise of 

the surface vessel motions. 

An autonomous underwater vehicle (AUV) is essentially a robotic submarine. An 

AUV can carry a gravimeter much closer to the features of interest. The underwater 

flight of an AUV is also much smoother than that of a surface vessel. On the other hand, 

an AUV presents challenges in terms of relatively limited endurance, payload capacity, 

and navigational uncertainties. With proper design, all of these problems can be 

overcome. 

We constructed and deployed a prototype gravimeter on board the SIO Bluefin 

AUV in June 2008. Initial results are encouraging, although the data analysis is still ongoing. 

Further testing and instrument improvements are being actively pursued. 

Figure 3. AUV and gravimeter checkouts during the June 2008 test cruise


Ballu, V., J. Ammann, O. Pot, O. de Viron, G. Sasagawa, G. Reverdin, M.N. Bouin, M. 

Cannat, C. Deplus, S. Deroussi, M. Maia and M. Diament. A seafloor experiment 

to monitor vertical deformation at Lucky Strike volcano, Journal of Geodesy, in 

press, 2008. 

Eiken, O., T. Stenvold, M. Zumberge, H. Alnes, G. Sasagawa, Gravimetric monitoring of 

gas production from the Troll field, Geophysics, in press, 2008. 

Nooner, S. L., Eiken, O., Hermanrud, C., Sasagawa, G. S., Stenvold, T., Zumberge, M. 

A., "Constraints on the in situ density of CO2 within the Utsira formation from 

time-lapse seafloor gravity measurements." Int. J. of Greenhouse Gas Control, 1, 

198-214. 2007. 

Sasagawa, G., M. Zumberge, O. Eiken, Long Term Seafloor Tidal Gravity and Pressure 

Observations in the North Sea: Testing and Validation of a Theoretical Tidal 

Model, Geophysics, in press, 2008. 

Zumberge, M., H. Alnes, O. Eiken, G. Sasagawa, T.Stenvold, Precision of seafloor 

gravity and pressure measurements for reservoir monitoring, Geophysics, in press, 

2008.

Peter Shearer 


Email address: pshearer@ucsd.edu 


Research Interests: seismology, Earth structure, earthquake physics 

Peter Shearer’s research uses seismology to learn about Earth structure and earthquakes, both 

globally and in California. His global seismology research has involved the development of new 

analysis approaches to handle efficiently the large digital data sets that have emerged from the 

global seismic networks during the last 15 years or so. In particular, he has applied stacking 

(averaging) methods to improve signal-to-noise ratios and make visible features in the waveforms 

that are not obvious on single records. This approach has proven particularly useful in studying the 

upper-mantle discontinuities and mapping their topography and other properties. Recent work with 

postdoc Jesse Lawrence (now at Stanford) mapped the transition zone thickness at higher resolution 

than previous studies by implementing finite-frequency sensitivity kernels (Lawrence and Shearer, 

2008). Work with graduate student Christine Houser and Prof. Masters applied cluster analysis to 

long-period waveforms to produce new models of 3D velocity structure in the mantle and joint 

inversions for upper-mantle discontinuity topography (Houser et al., 2008a,b). Shearer also studies 

seismic scattering in the deep Earth (see Shearer, 2007, for a recent review), which provides 

sensitivity to small-scale structures that cannot be resolved with seismic tomography. Working 

with former student Paul Earle (USGS–Golden), he has developed stacking methods that work with 

high-frequency data and a Monte Carlo implementation of radiative transfer theory for modeling 

whole-Earth scattering. 

Shearer’s southern California work has focused mostly on improving earthquake locations 

using robust methods and waveform cross-correlation. Graduate student Guoqing Lin (now a 

postdoc at Wisconsin) was involved in this research and completed her thesis last year. In 

collaboration with Egill Hauksson at Caltech, she produced a new 3D crustal P and S velocity 

model for southern California (Lin et al., 2007a) and a catalog with precise locations for over 

400,000 earthquakes from 1981 to 2005 (Lin et al., 2007b). These results delineate fault structures 

in unprecedented detail and suggest that the southernmost San Andreas Fault dips to the northeast, 

providing a likely explanation for the observed offset in strain across the fault. Lin also observes an 

interesting correlation between seismicity and low Vp/Vs ratios in her crustal tomography model. 

Lin and Shearer’s relocated earthquake catalogs for southern California are now used by a number 

of researchers. For example, the relocations were used by Plesch et al. (2007) to help create the 

Community Fault Model (CFM), a database of fault geometries for southern California. 

Another research topic has involved experimenting with applying backprojection (reverse time 

migration) to seismic records in order to directly image seismic radiation from earthquake ruptures. 

This method has some advantages over conventional finite-source modeling—it requires fewer 

assumptions about the fault geometry, it works with high-frequency data, and its computational 

efficiency makes it ideal for near-real-time applications. Former postdoc Miaki Ishii (now at 

Harvard) used backprojection to study the 2004 M9.1 and 2005 M8.7 Sumatra earthquakes (Ishii et 

al., 2007), using aftershocks as empirical travel-time correction points along these massive 

ruptures. Contrary to earlier reports, she found no evidence for anomalously slow slip for the 

northern part of the 2004 rupture. Graduate student Bettina Allmann adapted the backprojection 

approach to work with local strong motion data for the 2004 M6 Parkfield earthquake and solved 

for a fully three-dimensional image of the source (Allmann and Shearer, 2007). She identified a 

burst of high-frequency radiation that occurred about 13 km northwest of the hypocenter and 5 s 

after rupture initiation (see Fig. 1). This event occurred at the south end of a large area of moment 

release seen in long-period slip inversions and likely represents an asperity (strong patch) that, once 

broken, permitted greatly increased slip to the north.

Figure 1. Images of high-frequency radiation from the 2004 Parkfield earthquake obtained using 

a backprojection technique applied to local strong motion records. Station locations are shown as 

the yellow triangles; the surface trace of the San Andreas Fault as the red line. The left panel 

shows energy radiating from the hypocenter at the beginning of the earthquake. The right panel 

shows radiation from a distinct subevent occurring 5 seconds later and 13 km northwest along the 

fault. From Allmann and Shearer (2007). 


Allmann, B. P., and P. M. Shearer, A high-frequency secondary event during the 2004 Parkfield earthquake, 

Science, 318, 1279, doi: 10.1126/science.1146537, 2007. 

Bulow, R. C., C. L. Johnson, B. G. Bills, and P. M. Shearer, Temporal and spatial properties of some deep 

moonquake clusters, J. Geophys. Res., 112, doi: 10.1029/2006JE002847, 2007. 

Houser, C., G. Masters, M. Flanagan, and P. Shearer, Determination and analysis of long-wavelength 

transition zone structure using SS precursors, Geophys. J. Int., 174, 178–194, doi: 10.1111/j.1365- 

246X.2008.03719.x, 2008a. 

Houser, C., G. Masters, P. Shearer, and G. Laske, Shear and compressional velocity models of the mantle 

from cluster analysis of long-period waveforms, Geophys. J. Int., 174, 195–212, doi: 10.1111/j.1365- 

246X.2008.03763.x, 2008b. 

Ishii, M., P. M. Shearer, H. Houston, and J. E. Vidale, Teleseismic P wave imaging of the 26 December 2004 

Sumatra-Andaman and 28 March 2005 Sumatra earthquake ruptures using the Hi-net array, J. Geophys. 

Res., 112, B11307, doi: 10.1029/2006JB004700, 2007. 

Lawrence, J. F., and P. M. Shearer, Imaging mantle transition zone thickness with SdS-SS finite-frequency 

sensitivity kernels, Geophys. J. Int., 174, 143–158, doi: 10,1111/j.1365-246X.2007.03673.x, 2008. 

Lin, G., P. M. Shearer, E. Hauksson and C. H. Thurber, A three-dimensional crustal seismic velocity model 

for southern California from a composite event method, J. Geophys. Res., 112, doi: 

10.1029/2007JB004977, 2007. 

Lin, G., P. M. Shearer and E. Hauksson, Applying a three-dimensional velocity model, waveform cross 

correlation, and cluster analysis to locate southern California seismicity from 1981 to 2005, J. Geophys. 

Res., 112, B12309, doi: 10.1029/2007JB004986, 2007. 

Plesch, A., J. H. Shaw, C. Benson, W. A. Bryant, S. Carena, M. Cooke, J. Dolan, G. Fuis, E. Gath, L. Grant, 

E. Hauksson, T. Jordan, M. Kamerling, M. Legg, S. Lindvall, H. Magistrale, C. Nicholson, N. Niemi, M. 

Oskin, S. Perry, G. Planansky, T. Rockwell, P. Shearer, C. Sorlien, M. P. Suss, J. Suppe, J. Treiman, and 

R. Yeats, Community fault model (CFM) for southern California, Bull. Seismol. Soc. Am., 97, 1793– 

1802, 2007. 

Shearer, P. M., Seismic scattering in the deep Earth, in Treatise on Geophysics, Volume 1: Deep Earth 

Structure, Schubert, G. (ed.), Elsevier Ltd., Oxford, p. 695-730, 2007.

Hubert Staudigel 

Research Geologist, Lecturer 

Email address: hstaudigel@ucsd.edu 

Personal website: http://earthref.org/whoswho/ER/hstaudigel/index.html 


Research Interests: Seamounts, Volcanology, Biogeoscience, Science Cyberinfrastructure and 

Education 

Seamounts have been a central theme in Hubert Staudigel’s research since his PhD work on 

the seamount series of La Palma, Canary Islands (Staudigel and Schmincke, 1984). Since then he 

has worked on numerous aspects of seamount science, from petrology and isotope geochemistry to 

their Mn encrustations, macrobenthic communities and microbiology, their magnetic properties, 

density distribution (gravity) and seismic structure. Over the last few years most of his seamount 

research focused on the geochronology, geochemistry and the microbial communities colonizing 

them, in particular around active hydrothermal vents. Recent papers include: (1) the source region 

characteristics of the Samoan Islands and the discovery of the of the most radiogenic (extreme) EM 

II composition of Samoa (Jackson et al.,2007), (2) the demonstration of a systematic age 

progression and the “hot-spot” origin of Savaii (Samoa; Koppers et al., 2008 ), and (3) An isotopic 

investigation of previously dated seamount samples in the Western Pacific (Konter et al., in press) 

showed that three recently active hot spot volcanoes in the Cook-Austral island chain have been 

consistently producing isotopically extreme magmas suggesting an origin by long-lived hot spots. 

Hubert Staudigels’ involvement in volcanology includes interests in submarine volcanism 

and dike intrusions and he also teaches a class in volcanology whereby the next class will be in 

2009 (the 2008 class was postponed due to Kilauea’s eruptive activity in the main caldera). Recent 

volcanological studies include the discovery of potentially the oldest ophiolite on earth in the Isua 

Supracrustal Belt (Furnes et al., 2007) and volcano-based paleomagnetic research in Antarctica in 

the McMurdo volcanic series (http://earthref.org/ERESE/projects/GOLF182/index.html, in 

collaboration with Lisa Tauxe, Cathy Constable and Kristin Lawrence). The key objective of the 

latter is to study the fine scale (secular) variation of the magnetic field, where the HS explores field 

relationships and the potential for volcano-tectonic disturbance of a paleomagnetic signal. 

Hubert Staudigel collaborates Brad Tebo, Alexis Templeton, Katrina Edwards, Craig 

Moyer and Dave Emerson and graduate students Brad Bailey and Lisa Sudeck (Haucke) to study 

the chemical and biological controls of water-rock interaction during seafloor alteration of the 

oceanic crust. Current work focuses on the characterization and isolation of microbes that facilitate 

these processes (Santelli et al., 2008) and the mechanisms by which microbes may dissolve in 

particular volcanic glass. In collaboration with H. Furnes (U. Bergen, Norway) and others Hubert 

Staudigel studied characteristic corrosion that is imposed by microbial activity on natural basaltic 

glass, and they could show that the majority of glass alteration is caused by microbial activity, in 

the upper 300m of the oceanic crust of all ages in the ocean basins, back through time to almost 3.5 

Ba (Staudigel et. al., 2008). Hubert Staudigel recently obtained funding to study microbe-rock 

interaction in the McMurdo extreme environments of Antarctica, where he will lead three field 

seasons in the 2008/9, 20010/11 and 20012/13 seasons, with co-PI Laurie Connel of U. Maine. 

Hubert Staudigel is also involved in efforts creating a Cyberinfrastructure for earth science 

and science education, in collaboration with A. Koppers, J. Helly, C. Manduca and D. Mogk. Key

data base components include the reservoir data base for the Geochemical Earth Reference Model 

(GERM) initiative, the Seamount Catalog for the Seamount Biogeoscience Network (SBN) and the 

ERESE project (Enduring Resources for Earth Science Education), all accessible at earthref.org. 

Collaboration with K. Manduca of the Science Education Resource Center (SERC) at Careleton 

College (http://serc.carleton.edu/sp/erese/activities.html). Hubert Staudigel’s website includes a 

more complete bibliography (http://earthref.org/whoswho/ER/hstaudigel/index.html). 


Banerjee N.R., A. Simonetti, H. Furnes, K. Muehlenbachs, H. Staudigel, L. Heaman and M. J. Van 

Kranendonk (2007). Direct dating of Archean microbial ichnofossils. Geology. Geology, June 

2007; v. 35; no. 6; p. 487–490; doi: 10.1130/G23534A.1. 

Furnes, H., M. de Wit, H. Staudigel, M. Rosing, K. Muehlenbachs (2007) A Vestige of Earth's 

Oldest Ophiolite. Science 23 March 2007: 1704-1707. DOI: 10.1126/science.1139170 

Furnes, H., M. de Wit, H. Staudigel, M. Rosing, K. Muehlenbachs, 2007, Response to Comments 

on Vestige of Earth's Oldest Ophiolite”. Science 2 Movember 2007: 746E. 

Jackson et al., 2007 Jackson, M. G., S. R. Hart, A.A. P. Koppers, H. Staudigel, G., J. Konter, J. 

Blusztjan, M. Kurz, and J.A. Russell, The return of subducted continental crust in Samoan lavas. 

Nature 448, 684-687| doi:10.1038 

Konter, J.G., B. Hanan; J. Blichert-Toft; A. Koppers; T. Plank, H. Staudigel, 2008, One hundred 

million years of mantle geochemical history suggest the retiring of mantle plumes is premature., 

Earth Planet. Sci. Lett., 2008 in press. 

Koppers, A.A.P, Staudigel, H. J. Phipps Morgan, Robert A. Duncan, 2007, Non-linear 40Ar/39Ar 

Age Systematics Along the Gilbert Ridge and Tokelau Seamount Trail and the Timing of the 

Hawaii-Emperor Bend. G-cubed VOL. 8, Q06L13, doi:10.1029/2006GC001489, 2007 

Koppers, AAP, J.A. Russell, M. G. Jackson, J. Konter, H. Staudigel, S. R. Hart, 2008, Samoa 

reinstated as a primary hotspot trail, Geology, v. 36; no. 6; p. 435–438; doi: 10.1130/G24630A.1; 4 

fi gures; Data Repository item 2008102008 . 

Reisberg, L., O. Rouxel, J. Ludden, H. Staudigel, C. Zimmermann, 2008, Re-Os results from ODP 

Site 801: Evidence for extensive Re uptake during alteration of oceanic crust. Chemical Geology, 

248 256–271 

Santelli, CM, B. N. Orcutt, Banning, E., Bach, W., Moyer, C.L., Sogin, M.L., Staudigel, H., 

Edwards, KJ, 2008, Abundance and diversity of microbial life in ocean crust Nature Vol 453|29 

May 2008| doi:10.1038/nature06899 

Staudigel, H., H. Furnes, N. McLoughlin, N. R. Banerjee, L. B. Connell, A.Templeton, 2008, 3.5 

billion years of glass bioalteration: Volcanic rocks as a basis for microbial life? Earth-Science 

Reviews (2008), doi:10.1016/j.earscirev.2008.04.005

Lisa Tauxe 


Email address: ltauxe@ucsd.edu 


Research Interests: My research over the past year has been in a few major themes: 1) obtaining new data 

to contrain the statistical properties of the secular variation of the geomagnetic field, 2) applications of 

statistical models of the geomagnetic field for purpose of diagnosing and compensating for sedimentary 

errors in magnetic recording processes, 3) variations in the strength of the geomagnetic field over the past 

seven millennia as recorded in Israeli and Jordanian copper mining slag heaps, 4) and developing the 

theory, practical experimental design and assembling the data sets of paleointensity records of the 

geomagnetic field. 

We finished a major effort in topic #1 above by compiling data from over 100 lava flows 

sampled in three field seasons since 1965 (Lawrence et al., 2008; see Figure 1). Data from lava flows 

originally collected in the 1965/1966 field season by Ed Mankinen and Alan Cox were reanalyzed by 

Tauxe et al. (2004) and re-interpreted and combined with data from two field seasons conducted in 

2003/2004 and 2006/2007 in 

Lawrence et al. (2008). 

Figure 1: Shaded relief map of the 

southern portion of the Western 

Ross Embayment projected as conic 

equal area and illuminated from 

N/NW. Red (yellow) circles 

represent data collected in the 

2003/04 (2006/2007) field season 

and presented in this study. Blue 

circles represent data presented in 

Tauxe et al. [2004]. Small inset is 

the same projection of the 

Antarctica continent. [Figure from 

Lawrence et al., 2008.] 

There are several reasons why paleomagnetic data from high latitudes are important. The first 

is that models of paleosecular variation have long sought to explain the distributions of paleomagnetic 

directions (and their equivalent virtual geomagnetic poles). These are strongly constrained by scatter in 

directions observed at high latitude. A second reason is that the first order prediction for variations in 

field strength as a function of latitude is that polar regions should be, on average, twice as strong as 

equatorial regions. 

Despite their value, data from high latitudes (> ±70°) were scare and intensity data were 

entirely absent before we began our work. Our data revealed two surprises. First, scatter from 

paleosecular variation was larger than that predicted by all recent statistical paleosecular variation 

models (see e.g., Johnson et al., 2008). Second, and more startling, was that the expected increasing 

trend in intensity data with latitude was absent (see data in Figure 2a) which if anything suggest a 

weakening of the field at latitudes greater than ± 65°.

The explanation for this entirely unexpected behavior is not known. It could arise from 

inadequate temporal and geographic sampling of the geomagnetic field. It is also possible that the 

influence of the presence of a solid inner core on the generation of the geodynamo in the fluid outer 

core. The convective regimes inside a cylinder parallel to the spin axis that is tangent to the inner core 

(the tangent cylinder) are thought to be different (see Figure 2b) and it is possible that the suppression 

of field strength at high latitudes results from these differences. 

Figure 2: (a) Paleointensity vs. latitude of the Pint06 database (grey crosses) [Tauxe and Yamazaki, 

2007] and paleointensity estimates from Lawrence et al. (2008, red crosses) for data with ages less than 

5 Ma, dσB ≤ 15 µT, and Nsite ≥ 2. Mean paleointensity results (black diamonds) are calculated for 15◦ 

latitude bins and errors are shown as 2σ. The vertical dashed line is the surface expression of the edge of 

the tangent cylinder. The locations of the paleointensity results are shown in the inset with the Antarctica 

data set as a red triangle. Southern hemisphere data have been flipped to the Northern hemisphere. The 

blue dashed line represents the intensity associated with a geocentric axial dipole with a dipole term of 

30 µT. b) Sketch showing location of tangent cylinder, and different dynamical regimes. [Figure modified 

from Lawrence et al., 2008.] 


Johnson, C.L., Constable, C.G., Tauxe, L., Barendregt, R., Brown, L.L., Coe, R.S., Layer, P., Mejia, V., 

Opdyke, N.D., Singer, B.S., Staudigel, H., Stone, D.B., 2008, Recent investigations of the 0-5 Ma 

geomagnetic field recorded by lava flows, Geochem. Geophys. Geosyst., 9, Q04032, 

doi:10.1029/2007GC001696. 

Lawrence, K.P., Tauxe, L., Staudigel, H., Constable, C.G., Koppers, A., McIntosh, W., Johnson, C.L., 

2008, Paleomagnetic field properties near the southern hemisphere tangent cylinder, Geochem. 

Geophys. Geosys., in press, 2008. 

Tauxe, L., Kodama, K.P., Kent, D.V., 2008, Testing corrections for paleomagnetic inclination error in 

sedimentary rocks: a comparitive approach, Phys. Earth Planet. Int., doi:10.1016/j.pepi.2008.05.006. 

Tauxe, L. and Yamazaki, T., 2007, Paleointensities, in: Treatise on Geophysics, Schubert, G. (ed.), vol. 5, 

Geomagnetism, 509-564, Oxford: Elsevier Ltd.

Michael Tryon 


Email address: mtryon@ucsd.edu 


Web page: http://TryonLab.ucsd.edu 

Research Interests: The marine hydrogeology of cold seeps, mud volcanoes, and submerged faults, the 

physical processes associated with the structural evolution of convergent margins, and the development 

of new seafloor instrumentation for these purposes 

Michael Tryon’s research investigates the physical and chemical interactions between ocean margin 

tectonics and hydrologic systems through the use of novel instrumentation. This work is primarily 

focused on investigating the driving forces, rates of flow, sources of transience, geochemical 

characterization, and influence on biology of near-surface hydrologic systems. The foundation for this 

work is the instrument he developed which records a temporal record of fluid flow rates of as little as 

0.1 mm/yr along with time-series samples of the expelled fluid and dissolved gases for later analysis 

(Tryon et al., 2001). 

Michael is currently a PI on two large-scale field-research projects. The MARNAUT Project is an 

international collaboration utilizing a wide array of geophysical and hydrological techniques to study 

the manifestations of fluid expulsion associated with the Main Marmara Fault, the submerged western 

extension of the North Anatolian Fault Zone in Turkey, with the theme of understanding the 

relationship between seismic activity and fluid migration/expulsion processes along this active plate 

boundary. The first leg of this project was carried out in June of 2007 with the French research vessel 

l’Atalante and the submersible Nautile and deployed 7 Scripps flow meters for one year. This is the 

first exploratory stage of what is hoped to become a full-time seismic and hydrologic cabled 

observatory as part of a geohazards monitoring and warning system within the scope of the European 

ESONET program. Stage two begins in 2009 with deployment of 3 multidisciplinary observatories in 

the MARMARA-DM project. Our initial results confirm a direct relationship between seafloor faults 

and gas emissions with active expulsion tied to earthquake activity and seismic gaps associated with a 

lack of gas expulsion (Géli et al., 2008). 

Mud volcanism is a common phenomenon in different continental margin settings, especially in deltaic 

depositional systems worldwide. Fluid formation and fluidization processes occurring at depths of 

several kilometers below the seafloor can be monitored in mud volcanoes acting as natural leakages for 

oil and gas reservoirs. To gain a better understanding of deep processes occurring in the West Nile 

Delta area Michael is carrying out a study on two mud volcanoes in collaboration with IFM-GEOMAR 

as part of The West Nile Delta Project. This project focuses on qualifying the chemical and isotopic 

composition of pore fluids as well as investigations of light volatile hydrocarbon gases and organic 

biomarkers and the quantification of the variability of dewatering and degassing through long-term 

flow rate and chemical flux measurements. Deployments of flow meters, gas and fluid samplers, pore 

pressure sensors, and heat flow surveys are scheduled for Fall 2008 through Summer 2010. 

Michael also has two instrument development projects ongoing. The first of these is the development 

of an ocean bottom 3-D strain meter, “GEOCE”, in collaboration with K. Brown, D. Chadwell, and U. 

Send, all at Scripps. Tryon’s portion of this project uses high resolution pressure measurements and a 

seafloor pressure standard to determine the vertical motion of the seafloor in response to deformation

and/or gravitational sliding. The second project is the development of a new generation of seafloor 

piezometers for both long-term monitoring of the hydrological response to tectonic strain and for 

geotechnical investigations. These instrumentation development programs will allow us to monitor the 

most critical properties (stress and strain) of continental margins to improve our understanding of the 

underlying tectonics and for evaluation of their potential for catastrophic failure. 

Relevant Recent Publications 

Tryon, M.D., 2008, Monitoring aseismic tectonic processes via hydrologic responses: An analysis of logperiodic 

fluid flow events at the Costa Rica outer rise, Geology, in press, September 2008. 

Géli, L., P. Henry, T Zitter, S. Dupré, M. Tryon, M.N. Çagatay, B. Mercier de Lépinay, X. Le Pichon, 

AMC Sengor, N. Görür, B. Natalyn, G. Uçarkus, S. Özeren, D. Volker, L. Gasperini, P. Bernard, S. 

Bourlange, and the Marnaut Scientific Party, 2008, Gas emissions and active tectonics within the 

submerged section of the North Anatolian Fault zone in the Sea of Marmara, Earth and Planetary 

Science Letters, 274, 34-39. 

La Bonte, A.L., Brown, K.M., Tryon, M.D., 2007, Monitoring periodic and episodic flow events at 

Monterey Bay seeps using a new optical flow meter, Journal of Geophysical Research, 112, B02105, 

doi:10.1029/2006JB004410. 

Brown, K.M., M.D. Tryon, H.R. DeShon, L.M. Dorman, and S. Schwartz, 2005, Correlated Transient 

Fluid Pulsing and Seismic Tremor in the Costa Rica Subduction Zone, Earth and Planetary Science 

Letters, 238, 189-203.

Frank Vernon 

Research Scientist 

Email address: flvernon@ucsd.edu 


Research Interests: Time Series Analysis, Earthquake Source Physics, Seismometer Design, Real-Time 

Sensor Networks, Ocean Observing Systems 

We operate the USArray Array Network Facility (http://anf.ucsd.edu), which is a key 

component for the NSF EarthScope MRE. This network currently has 434 seismic stations 

delivering real-time data to UCSD, which are redistributed to multiple sites. The ANF is 

responsible for real-time state-of-health monitoring for the network in addition to the real 

time data processing, archiving, and distribution. Data are acquired over multiple types of 

communication links including wireless, satellite, and wired networks. The large volumes of 

broad band waveform data from the transportable array element of 

USArray offers a unique opportunity for seismic imaging. Constraining structures on 

a range of length scales 

and understanding their 

physical and chemical 

causes is a prerequisite 

for understanding the 

relationship between 

near surface and deeper 

mantle processes. With 

existing methods, 

we can produce 3-D 

models of P wavespeed 

variations in the mantle 

beneath North America 

using travel times 

from the USArray 

TA . This is just one 

example of the many 

scientific opportunities 

provided by this unique 

experiment. 

S p e c t r a l 

analysis has undergone 

a revolution with 

the development of 

Figure 1. Results from body wave tomographic imaging using 

USArray. Top left the panels show grid resolution, top right checkboard 

test, bottom shows map views at 100 km and 200 km depth. 

The middle panel shows three cross-sections. 

sophisticated techniques in which the data are multiplied in turn by a set of tapers that are 

designed to maximize resolution and minimize bias. In addition to minimizing the bias while 

maintaining a given resolution, the multi-taper approach allows an estimate of the statistical 

significance of features in the power spectrum. We are developing a quadratic inverse theory 

that utilizes not only the spectral estimators, but also the time and frequency derivatives of

the spectrum, to generate much higher resolution spectra. We are extending the theory from a 

univariate to a generalized multivariate theory. While the specific applications researched here 

are seismic, it is clear that there are other geophysical, scientific, and engineering applications 

that will benefit from the proposed studies. 

Another result based on multitapers is are 

some unanticipated effects of the normal modes 

of the sun on engineering and scientific systems. 

Our results, based on extensive time-series 

studies of diverse data sources from operational 

communication and other engineered systems as 

well as the natural environment, show that much 

of the phenomena observed in space physics, 

including geomagnetic and ionospheric 

phenomena, exhibit a multitude of discrete 

frequencies over a wide frequency range 

superimposed on a noise background. We have 

hypothesized that these discrete frequencies 

can be explained in terms of the normal modes 

of the sun (solar theory, confirmed by data 

from helioseismology instruments that resolve 

spatial structure on the sun, shows that there 

are several million solar modes). That is, the Spectral peaks in seismic data at solar 

normal modes of the sun are a dominant driver 

of the discrete frequencies that are measured in 

mode frequencies. 

natural phenomena and also of the “noise” in engineered systems. 

A key research project is the ROADNet program (http://roadnet.ucsd.edu) which is 

focused on developing the real-time cyberinfrastructure to acquire, process, distribute, and 

archive data from environmental, oceanographic, geophysical, and structural monitoring sensor 

nets, many of which are accessed through HPWREN. 


Prieto, G. A. , D. J. Thomson, F. L. Vernon, P. M. Shearer and R. L. Parker (2006). 

Confidence intervals of earthquake source parameters, Geophys. J. Int., doi: 10.1111/j.1365- 

246X.2006.03257.x, Published online. Schulte-Pelkum, V., P. S. Earle, and F. L. Vernon (2004), 

Strong directivity of ocean-generated seismic noise, Geochem. Geophys. Geosyst., 5, Q03004, 

doi:10.1029/2003GC000520. 

G. A. Prieto, R. L. Parker, F. L. Vernon, P. M. Shearer and D. J. Thomson (2007). Uncertainties 

in Earthquake Source Spectrum Estimation using Empirical Green Functions. AGU Monograph 

on Radiated Energy and the Physics of Earthquake Faulting , R. E. Abercrombie, A. McGarr, 

H. Kanamori, and G. di Toro eds. Doi: 10.1029/170GM08 69-74. 

Prieto, G. A., R. L. Parker, D. J. Thomson, F. L. Vernon and R. L. Graham (2007). Reducing the 

bias of multitaper spectrum estimates. Geophys. J. Int., 171,1269-1281, doi: 10.1111/j.1365- 

246X.2007.03592.x 

Thomson, D. J., L. J. Lanzerotti, F. L. Vernon, III, M. R. Lessard, and L. T. P. Smith (2007). 

Solar Modal Structure of the Engineering Environment. Proc. IEEE, 95,1085-1132, Doi: 

10.1109/JPROC.2007.894712

Martin Wahlen 


Email address: mwahlen@ucsd.edu 


Research Interests: Reconstruction of paleoatmosphere from ice cores, global biogeochemical cycles 

of atmospheric trace gases 

Constraining the global budget of nitrous oxide through stable isotopes 

Nitrous oxide (N2O) in the atmosphere is a long lived (τ ~150 yrs) potent greenhouse gas and a 

stratospheric ozone regulator. The stable isotope composition ( 15 N/ 14 N, 18 O/ 16 O) in nitrous oxide from 

different sources is markedly different, and the stratospheric sink reactions considerably fractionate the 

stable isotopes. Therefore measurements of the stable isotope composition (besides the mixing ratios) 

and their time variations can help to estimate the strengths of sources and sinks. 

We observe consistent continuous trends in the isotopic composition of this trace gas over several years 

in "clean" air samples collected approximately weekly from the end of the SIO pier. N2O is separated 

from the whole air samples and the isotopes are measured by high precisioin isotope ratio mass 

spectrometry, and compared to international standards. The observed trends are towards lower (lighter 

and decreasing) isotope ratios in both N and O at ~-1 permil/year. This time trend is most likely caused 

by an increasing production of N2O by catalytic converters in cars (supported by additional auxiliary 

data), and/or from increasing N2O production in shallow waterlogged environments such as from rice 

cultivation and from tundra (permafrost melting in the Arctic). All these processes are influenced by 

human activities, and contribute to the rising atmospheric inventory. 


Rahn, T. and M. Wahlen, 2002, Mass spectrometric method for the determination of the stable isotopic 

content of nitrous oxide by the technique of direct injection, in: International Atomic Energy Agency 

TECHDOC-1268: Stable isotope measurement techniques for atmospheric green house gases, 47-57. 

Ahn, J., Wahlen, M., Deck, B.L., Brook, E.J., Mayewski, P.A., Taylor, K.C. and J.W.C.White, 2004, A 

record of atmospheric CO2 during the last 40,000 years from the Siple Dome, Antarctica ice core, J. 

Geophys. Res.-Atmos., 109 (D13), D13305. 

Keeling, C., Piper, S., Bacastow, R., Wahlen, M., Whorf, T., Heimann, M. and H. Meijer, 2005, 

Atmospheric CO2 and 13 CO2 exchange with the terrestrial biosphere and oceans 1978 to 2000: 

Observations and carbon cycle implications, in: A history of atmospheric CO2 and its effect on plants, 

animals and ecosystems, Ehleringer, J., Cerling, T., Dearing, M., eds., Springer Verlag, 83-113. 

Ahn, J., Headly, M., Wahlen, M., Brook, E., Majewsky, P. and K. Taylor, 2008, CO2 diffusion in polar 

ice: observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core, J. 

Glaciology, 54, 685-695.

Brad Werner bwerner@ucsd.edu ||| http://complex-systems.ucsd.edu 

Research interests: complexity, nonlinear dynamics and pattern formation; permafrost terrain; dynamics of 

human systems and human-landscape interactions; urban landscapes; dynamics of “western” and 

indigenous science; resistance movements; and independent media. 

Brad Werner and co-workers Seth Lutske and Navjeet Sarna in the Complex Systems Laboratory have 

been working to develop and refine the tools used to investigate complex systems, those systems for which 

simple and complicated descriptions, and often a range of intermediate representations, can be constructed. 

Earth’s Surface in 200 Years 

What will Earth’s surface look like in 200 y? The vast changes that have occurred over the past 200 y and 

the accelerating pace of change suggest that knowledge of the current state and trends are insufficient for 

answering this question. Great progress has been made for physical/chemical and ecological dynamics, but 

large gaps exist in understanding human systems and their relationship to nonhuman natural processes. 

One goal of the Complex Systems Laboratory is to help fill these gaps by developing the analysis and 

computational tools, within the framework of studies of complexity and nonlinear dynamics, that are 

necessary to make useful predictions for the future of the coupled human/Earth surface system. A second 

goal is to democratize knowledge of complexity analysis tools, so that a broader range of people can 

participate in analyzing and shaping the future of Earth’s surface and the role of humans within its systems. 

Human Dynamics 

Discussions of human systems, ranging from the philosophizing of Deleuze to scientific studies of 

consciousness, commonly fail to account for the severe constraints that nonlinear/dissipative dynamics 

places on their possible states and outcomes. Analyses based on complexity lead to a number of insights: 

Economics: That most human relations, except at the smallest scales, are now governed by profit-seeking, 

commodifying market dynamics permits remarkable simplification in describing the interaction of billions 

of people, each of whom potentially could exhibit complicated behavior. Agent-based models, in which the 

actions of individual or groups are represented by rule-following agents, capture the intermediate- to longtime-scale 

behavior of heterogeneous humans as constrained by the market system. 

Political Systems and Managers: From a dynamical perspective, political systems reflect the feedbacks and 

power relations established within the economic system, with some notable differences. To zeroth order, 

political decisions are based on economic considerations, often explicitly through the use of cost-benefit 

analyses. These analyses and decisions made by resource and other managers tend to act as filters, 

introducing longer time scales and lags into decision making (having a stabilizing or destabilizing 

influence). The inherent nonlinearity of political processes can introduce biases and thresholds, generally 

favoring wealthy, organized entities over medium and longer time scales. Over short time scales, these 

biases are much more random, tending to make them difficult to perceive, measure or oppose. 

Free Will: Much of the literature on management of Earth’s subsystems and resources explicitly or 

implicitly assumes that individuals or people collectively can freely make decisions to influence the course 

of events. From a dynamical perspective, if free will decisions nontrivially exist, they manifest as extradynamical 

phenomena at fast, stream-of-consciousness time scales. They affect longer-time-scale 

dynamics only when they are applied at or near transitions, where the structure of phase space is flattish 

and a range of time scales are dynamically coupled so that these nondynamical kicks can influence the 

pathway and basin of attraction into which the system moves. The ability of humans to affect outcomes 

consciously is dependent on the dynamical context and, most likely, highly limited. 

Resistance: How can those who are concerned about the pathway of the coupled global human-landscape 

system intentionally influence its course? Enduring course changes are unlikely to arise from deck chair 

rearrangements performed by those deeply embedded in the dominant global economic/political system, 

because of the strong feedbacks operating on them and the tenuous nature of their positions, or from

esistance movements originating from within the system, because they tend to co-evolve with and be coopted 

by it (as evidenced by the dilution, distortion and neutralization of socialist and communist 

resistance). The pathway determined by an adaptable, powerful, global political/economic system coevolving 

with internal resistance can only be diverted by groups with solid footing insulated from that 

system, such as indigenous cultures or those living outside the formal economic system in megacity slums. 

Information Systems: Information systems ranging from corporate media to blogs, books and research 

articles tend to reflect economic and political relations over medium to longer time scales, with 

considerable variability over shorter scales, because of the ability of those with greater resources and 

power to steer and co-opt information streams. The dominant focus of mainstream information streams is 

short-time-scale phenomena, stabilizing the network of economic and power relations and resisting 

change, because these fast phenomena are somewhat randomized and decoupled from longer-term trends. 

Human-Landscape Interactions 

Humans are impacting Earth surface systems via strong effects on the atmosphere, hydrosphere, oceans 

and ecosystems, driven primarily by economic and political positive feedbacks involving land, mineral and 

ecological resources. Earth surface systems impact humans through episodic natural disasters and through 

regional and global trends, such as ecosystem change, soil and sediment transport, sea level rise, climate 

change and microbial evolution and pathogenesis. Humans and landscapes are nonlinearly coupled most 

strongly where fluvial, oceanic or atmospheric processes render significant stretches of human-occupied 

land vulnerable to large changes and damage, and where market processes assign value to the land and 

drive political measures to protect it from damage. These processes operate over the medium scale of many 

years to decades over which landscapes become vulnerable to change and over which markets drive 

investment in structures, evaluate profits from those investments and respond to changes in conditions. 

The Complex Systems Laboratory currently is investigating human-landscape dynamics by coupling 

models of landscapes with agent-based models of economic development. In a model for the interaction of 

barrier islands with agent-based models of market-driven tourism and resort development, storm damage 

to resorts and coastal hazard protection measures, market dynamics destabilize barrier island response to 

rising sea level, giving rise to emergent, episodic boom and bust cycles that alternate in phase alongshore. 

At longer time scales, redistribution of sediment used to counteract erosion syncs the boom and bust 

cycles, leading to regional resort destruction. A model for economic development, river and hurricaneinduced 

flooding, and levee building in New Orleans approximately reproduces historical expansion, 

flooding and increase in levee heights (with storm surge levees lagging river flood levees), as well as the 

occurrence of Katrina-scale floods-predicted to continue into the future. In-progress modeling projects 

include: interaction between wildfires and home development at the urban-wildland boundary; coupling 

between resource development, greenhouse gas emissions and climate; and widespread development of 

slums in megacities, largely sited in locations subject to hazards, such as landslides, floods and fires. 

Democratizing Dynamics 

The Complex Systems Laboratory is working to broaden access to the tools of complexity and nonlinear 

dynamics by: participating in community workshops and meetings; organizing complexity-related 

discussion groups; sharing technical and knowledge skills and equipment with community activists; 

meeting with on-the-ground resource managers; developing a park exhibit; and writing popular books on 

urban complexity and the dynamics of resistance. 

--B. T. Werner & D.E. McNamara (2007) Dynamics of coupled human-landscape systems, Geomorphology, 91, 393-407. 

--D.E. McNamara & B. T. Werner (2008) Coupled Barrier Island-Resort Model: 1. Emergent instabilities induced by strong 

human-landscape interactions, JGR-Earth Surface, 113, F01016, doi:10.1029/2007JF000840. 

--D.E. McNamara & B. T. Werner (2008) Coupled Barrier Island-Resort Model: 2. Tests and Predictions along Ocean City and 

Assateague Island National Seashore, Maryland, JGR-Earth Surface, 113, F01017, doi:10.1029/2007JF00084. 

--L.J. Plug & B.T. Werner (2007) Modelling of ice-wedge networks, Permafrost & Periglacial Processes, 19, 63-69. 

--D.E. McNamara & B.T. Werner (2008) Flood evolution and human response in a coupled landscape and economic model for 

New Orleans, Geophysical Research Letters, in preparation.

Peter F. Worcester 

Research Oceanographer and Senior Lecturer 

Email address: pworcester@ucsd.edu 


Research Interests: acoustical oceanography, ocean acoustic tomography, underwater acoustics 

Peter Worcester’s research is focused on the application of acoustic remote sensing 

techniques to the study of ocean temperature structure and circulation and on improving our 

understanding of the propagation of sound in the ocean, including the effects of scattering from smallscale 

oceanographic variability. 

Acoustic Thermometry. Large-scale temperatures in the North Pacific Ocean were measured 

by long-range acoustic transmissions over the decade 1996–2006 [Worcester et al., 2005]. Acoustic 

sources located off central California (1996–1999) and north of Kauai (1996–1999, 2002–2006) 

transmitted to receivers distributed throughout the northeast and north central Pacific. The acoustic 

travel times are inherently spatially integrating, which suppresses mesoscale variability and provides a 

precise measure of range- and depth-averaged temperature. The interannual, seasonal, and shorter 

period variability is large, with substantial changes sometimes occurring in only a few weeks. Linear 

trends estimated over the decade are small compared to the interannual variability and inconsistent 

from path to path, with some acoustic paths warming slightly and others cooling slightly. The 

measured travel times are compared with travel times derived from four independent estimates of the 

North Pacific: (i) climatology, as represented by the World Ocean Atlas 2005 (WOA05), (ii) objective 

maps of the upper ocean temperature field 

derived from satellite altimetry and in situ 

profiles, (iii) an analysis provided by the 

Estimating the Circulation and Climate of 

the Ocean project as implemented at the 

Jet Propulsion Laboratory (JPL-ECCO), 

and (iv) simulation results from a highresolution 

configuration of the Parallel 

Ocean Program (POP) model. The 

comparisons provide a stringent test of the 

large-scale temperature variability in the 

models. The differences are sometimes 

substantial, indicating that acoustic 

thermometry data can provide significant 

additional constraints for numerical ocean 

models. 

Figure 1. Comparison of measured travel times for transmissions from the Kauai source to receiver k 

at a range of approximately 3500 km (blue) with travel times calculated using sound-speed fields 

derived from the World Ocean Atlas 2005, objective maps combining in situ temperature profiles and 

sea surface height from satellite altimetry (Argo+TOPEX Map), the JPL-ECCO model, and the POP 

model (gray). For comparison, the trend in travel time corresponding to a 5 m°C/year change in 

temperature at the sound-channel axis is also shown (red).

North Pacific Acoustic Laboratory (NPAL). Over the last twenty years, long-range, deep-water 

acoustic experiments have been performed almost entirely in the relatively benign northeast and north 

central Pacific Ocean [Worcester and Spindel, 2005]. The NPAL Group is now preparing to conduct a 

yearlong experiment in the much more variable northern Philippine Sea in 2010–2011, preceded by a 

short-term Pilot Study/Engineering Test in April-May 2009. The experiment in 2010–2011 will 

combine measurements of 

acoustic propagation and 

ambient noise with the use of 

an ocean acoustic tomography 

array to help characterize this 

highly dynamic region. The 

tomographic measurements, 

when combined with satellite 

and other in situ measurements 

and with ocean models, will 

provide an eddy-resolving, 4-D 

sound-speed field for use in 

making acoustic predictions. 

The receivers include a new 

Distributed Vertical Line Array 

(DVLA) receiver that spans the 

water column. 

Figure 2. Overall mooring geometry of the 2010–2011 Philippine Sea Experiment, consisting of six 

250-Hz acoustic transceivers (T1, T2, … T6) and a new DVLA receiver. The array radius is 330 km. 

The goals are to (i) understand the impacts of fronts, eddies, and internal tides on acoustic 

propagation in this complex region, (ii) determine whether acoustic methods, together with satellite, 

glider and other measurements and coupled with ocean modeling, can yield estimates of the timeevolving 

ocean state useful for making improved acoustic predictions and for understanding the local 

ocean dynamics, (iii) improve our understanding of the basic physics of scattering by small-scale 

oceanographic variability due to internal waves and density-compensated small-scale variability 

(spice), and (iv) characterize the ambient noise field, particularly its variation over the year and its 

depth dependence. The ultimate goal is to determine the fundamental limits to signal processing in 

deep water imposed by ocean processes, enabling advanced signal processing techniques to capitalize 

on the three-dimensional character of the sound and noise fields. 


Worcester, P. F., Munk, W. H., and Spindel, R. C., Acoustic remote sensing of ocean gyres, 

Acoustics Today, 1, 11–17, 2005. 

Worcester, P. F., and Spindel, R. C., North Pacific Acoustic Laboratory, J. Acoust. Soc. Am., 

117, 1499–1510, 2005.

Mark A. Zumberge 


Email address: zumberge@ucsd.edu 


Research Interests: Measurement of gravity in the marine and subaerial environments, development 

of new seismic instrumentation, optical fiber measurements of strain and pressure 

A borehole strainmeter using optical fibers 

The measurement of Earth strain provides insight into a wide variety of geophysical processes, 

including tectonic deformation associated with earthquakes, volcanoes, ocean ridge spreading, and sea 

floor subduction. Strain measurements can also be used to monitor the flow of glacial ice (a problem 

to which optical fibers have proven to be particularly well suited), and they are applicable in 

geotechnical arenas such as hydrocarbon reservoir monitoring and the observation of sediment 

movements on the sea floor. 

In strain measurements there is an advantage for the length of the sensor to be large. Because 

strain is defined as ΔL/L, strain noise is smaller for a given displacement (ΔL) noise if the instrument 

length L is long. In geophysical applications, noise in ΔL often results from imperfect coupling to the 

ground. Increasing the sensor length lessens this impact. Optical fibers have the advantage that optical 

methods can be applied to detect a very small ΔL even when L is large. They are therefore useful for 

strain measurements. The main drawback to optical fibers as strain sensors is the temperature 

coefficient of the index of refraction (about 10 -5 °C -1 ). 

Figure 1: This is a cut-away 

view of an optical fiber 

strainmeter deployed at the 

SAFOD (San Andreas Fault 

Observatory at Depth) 

borehole near Parkfield, 

California. First an outer 

casing was installed as the 

borehole was drilled to 

several km depth and then 

angled to pierce the San 

Andreas Fault. Later an inner 

casing was inserted, which 

extends to greater depths. We 

took this opportunity to install 

an experimental borehole 

strainmeter. Within the green 

cable shown at left, two 

optical fibers are stretched to 

800 m depth and cemented 

into the space between the 

inner and outer casings, where 

they won’t interference with 

other activity in the borehole.

Laser light is sent down one optical fiber and back up the other. At the surface the light 

interferes with a reference beam. As Earth strains and changes the length of the stretched optical 

fibers, the phase of the light that passes through them changes causing a fluctuation in light intensity 

recorded by a photodetector. These variations in light level are analyzed with a digital signal 

processor to yield a recording of the total length with nanometer resolution. 


An important target of 

this type of measurement is 

the seafloor, where conventional 

instrumentation is 

difficult or impossible to 

operate. It is hoped that 

optical fiber sensing techniques 

like this one will 

enable strain measurements to 

be made near seafloor tectonic 

features. 

Figure 2. We have received 

funding to build a second 

optical fiber borehole 

strainmeter at our high desert 

station: Piñon Flat 

Observatory. One problem 

with our SAFOD sensor is 

from thermal noise caused by 

air temperare variations above 

the ground, where the sensing 

fiber is exposed. In our new 

instrument, all of the sensitive 

parts of the instrument will be 

within the borehole, where the 

temperature is quite stable. 

Blum, J. A., Nooner, S. L., Zumberge, M. A., “Recording Earth strain with optical fibers.” IEEE 

Sensors Journal, 8 (2008): 1152 – 1160. 

Zumberge, M. A., “Geophysical applications of optical fiber sensors.” In: Fiber optic sensors and 

applications V, Eric Udd ed., Proc. SPIE, 6770, (2007);0, 67700Q-1, 67700Q-9.

Institute of Geophysics and Planetary Physics, SIO/UCSD 

9500 Gilman Drive, La Jolla, CA 92093-0225 

igpp.ucsd.edu 

Geosciences Research Division, SIO/UCSD 

9500 Gilman Drive, La Jolla, CA 92093-0220 

grd.ucsd.edu 

Image: Terrestrial LIDAR (LIght Detection And Ranging) scans of the sea cliffs along Torrey Pines State beach. Two geologic formations are imaged, the basal Del 

Mar Formation and the overlying Torrey Formation. Note the different styles of erosion for the two different formations. In addition to establishing a baseline from 

which future erosion can be assessed, we are surveying numerous failures to determine how fast they are reworked by wave erosion. Dark semicircles denote scanner location 

along the beach, and are 40 m apart for scale. Funding for this research was provided by California SeaGrant. The LIDAR images were collected by Michael 

Olsen and Elizabeth Johnstone.

Earth Section - Scripps Institution of Oceanography

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