PDF version of slides. - IRIS

Under the Sea:  

Ocean Bottom Seismology for 

Landlubbers" 

Douglas Wiens! 

Washington University in St. Louis!

Needed: Seismographs in the Oceans 

Exis%ng Permanent Seismic Sta%ons 

IRIS GSN 

 

Australia 

 

Canada 

 

International Federation of 

Digital Seismograph Networks 

 

 

6/2008 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

France 

 

 

Germany 

 

 

Italy 

 

Japan 

U.S. 

 

Other 

 

Proposed Ocean Seismic Network 

(Purdy and Dziewonski, 1989) 

Never Implemented!

Tectonic Processes Require Ocean Bo:om 

Observa=ons 

Seismogenic Zone 

Recycling and Magma Produc=on 

Sea Floor Spreading

Outline 

• Ocean Bo:om Seismograph Basics 

• Data Quality 

• How to Propose and Execute an OBS Project 

• Data Analysis and Results from OBS 

deployments

Two basic types of OBSs 

Broadband (Long Term) 

Short Period 

Broadband or semi-‐broadband sensor 

Sensor detaches from main package 

Dura=on up to 1.5 years 

Heavier, more expensive 

Generally 4.5 Hz sensor 

Dura=on 1-‐6 months 

Lighter, cheaper, and easier to deploy 

Used for ac=ve source and microseismicity

Typical Broadband OBS

US Broadband OBSs – Three types 

Woods Hole Scripps Lamont-‐Doherty 

Guralp CMG-‐3T sensors 

Quanterra Q330 datalogger 

Uses somewhat more ba:eries 

Nanometrics T240 sensors 

Custom datalogger 

10 OBSs have syntac=c foam 

MP L4 1-‐Hz sensors 

(with custom amplifier) 

Custom Datalogger 

Q330 customized 

In glass sphere 

All Provide 4 data channels: 

BHZ, BH1, BH2 (horizontals unoriented) 

DPG – differen=al pressure gauge

Innova=on – new developments 

Trawl Resistant OBSs 

for Shallow Water 

A:aching Magnetometer 

For MT Data Collec=on 

SIO Abalone 

LDEO TRM

Data Quality – Seismic Noise 

Borehole Seafloor Seismograph – OSN1 

High Noise 

Model (land) 

< 1 s – very quiet 

2-‐10 s -‐ microseism peak 

10-‐30 s – quiet 

> 30 s -‐-‐ noisy 

Seafloor instruments show 

more noise than the borehole 

at T < 1 s and T > 30 s. 

Buried sensors perform 

almost as well as borehole 

LP noise caused by 

-‐ Currents & =lt on horizontals 

-‐ Pressure varia=ons on ver=cal

Long-‐Period Noise on the Ver=cal 

Component 

Comparison of Land and Seafloor Noise 

Coherence-‐ Displacement and Pressure 

Water waves Low noise band Microseisms 

Water 

waves 

Microseisms 

Low noise 

band 

Bromirski, et al, 2013 

Red -‐ coherence during Rayleigh arrival 

Blue -‐ coherence when no earthquake arrival 

Bell and Forsyth, in prep

Removal of LP Water Wave Noise -‐ 

Examples 

• Calculate transfer func=on between pressure from DPG and Ver=cal displacement 

• Use transfer func=on to remove noise from pressure fluctua=ons 

• Transfer func=on (compliance) contains informa=on about elas=c proper=es 

Webb and Crawford [1999] 

Bell and Forsyth, in prep 

25 – 125 s bandpass 67 – 125 s bandpass

Data quality -‐ =ming 

• OBS’s have low power high quality clocks with drim rates 0.3 – 1 s/yr 

• Clocks are synced with GPS before amer recovery to get total drim 

• Time is then corrected assuming a linear drim rate. 

• Problem: the true drim may not be perfectly linear 

• Implica=ons: 

-‐-‐ Not significant for large-‐scale deployments for earth structure 

-‐-‐ Can become problema=c for microseismicity, closely spaced arrays 

• Atomic clocks are being inves=gated as a possible solu=on

Horizontal Component Orienta=on 

• Horizontal component orienta=ons are generally unknown at recovery 

• If airguns are used, then best results come from the par=cle mo=ons of the water wave 

• If no airguns, then P or Rayleigh polariza=ons from known earthquakes can be used 

• Rayleigh wave polariza=ons seem to work best 

• Stachnik et al [2012] outline a good method: 

-‐ assume some angle rela=ve to H1 and H2 is the radial component 

-‐ take the Hilbert Transform of the assumed radial component to remove phase shim 

-‐ compute the correla=on between the assumed radial component and the ver=cal 

-‐ loop over possible angles, highest correla=on coefficient gives the Rayleigh polariza=on

How to Propose and Execute an OBS 

Experiment 

• Good planning during proposal prepara=on is 

a key to success 

• Array planning: Need to carefully evaluate the 

scien=fic issues, the analysis techniques to be 

used, and the configura=on and # of OBSs 

needed 

• Fill out request forms for the OBS facility and 

the UNOLS ship facility and include in the 

proposal

Array Planning 

• Array planning for passive OBSs is similar to land 

experiment planning, but several differences 

• Cost: is a factor and limits the size of the arrays. The largest 

experiments are generally around 50 OBSs. Approx $12K/BB 

inst 

• Ship =me: is expensive and ships travel slowly (~ 12 knts) 

• Water Depth: Standard OBSs can be deployed from 1-‐5 km. 

Shallow (< 1 km) and deep (5-‐6 km) necessitate par=cular 

equipment. Currently cannot deploy at depths greater than 6 

km. 

• Dura=on: Some OBSs may technically be able to operate for 

18 months, but reliability and =ming accuracy goes down with 

dura=on. The normal limit is 12 months.

Addi=onal Considera=ons 

• There may not be any data return from a given OBS. 

Generally data return from recent experiments is 

about 90%, but can be < 50%. 

• The experiment must be designed so the complete 

failure of 10-‐20% OBSs does not undermine the 

objec=ves 

• Longer dura=on deployments, with a equipment swap 

amer one year, are possible but NSF may be reluctant 

to commit to a series of cruises in a remote area 

• OBSs can now record at high enough sample rates (~ 

100 sps) or change sample rate during the experiment 

so joint ac=ve-‐source/passive recording experiments 

are possible.

Broadband Array Example 

Lau Basin Ridge2000 

Experiment 

• Two high-‐density lines for detailed 2D 

body wave tomography 

• 2D ac=ve source array along the 

Eastern Lau Spreading Center 

• Embedded in 2D array for lower res 

3D tomography, surface waves, EQs 

• Surrounded by land BB seismographs 

• Also included “add-‐on” Japanese OBEM 

experiment

A ship track and cruise 

=metable is required 

D. Lizarralde’s map and spreadsheet – Mariana Trench experiment 

Distance Time Time Cummulative 

Institution BB SP Teth notes (km) (Days) (Hours) Days Date 

OBS ship: Cruise 1 

Depart 1/26/12 10:00 

Transit Guam to B03 472 1.01 24.27 1.0 1/27/12 10:16 

OBS Deployment 

Rosette test 0.46 11.04 1.5 1/27/12 21:18 

Deploy B03 SIO 1 T240 0 0.03 0.75 1.5 1/27/12 22:03 

Deploy B04 LDEO 1 T sensor 59 0.16 3.78 1.7 1/28/12 1:50 

Deploy L01 SIO 1 14 0.05 1.22 1.7 1/28/12 3:03 

Deploy B05 LDEO 1 52 0.14 3.42 1.9 1/28/12 6:29 

Deploy W10 WHOI 1 20 0.06 1.53 1.9 1/28/12 8:01 

Deploy S01 WHOI 1 61 0.15 3.64 2.1 1/28/12 11:39 

Deploy S02 SIO 1 20 0.06 1.53 2.1 1/28/12 13:11 

Deploy S03 SIO 1 20 0.06 1.53 2.2 1/28/12 14:42 

Deploy S04 SIO 1 20 0.06 1.53 2.3 1/28/12 16:14 

Deploy S05 SIO 1 20 0.06 1.53 2.3 1/28/12 17:46 

Deploy S06 SIO 1 20 0.06 1.53 2.4 1/28/12 19:17 

Deploy S07 WHOI 1 1 20 0.10 2.30 2.5 1/28/12 21:36 

Deploy S08 LDEO 1 1 1-yr 20 0.10 2.30 2.6 1/28/12 23:54 

Deploy S09 WHOI 1 1 20 0.10 2.30 2.7 1/29/12 2:12 

Deploy S10 LDEO 1 1 1yr 20 0.10 2.30 2.8 1/29/12 4:30 

Deploy L04 WHOI 1 1 34 0.13 3.02 2.9 1/29/12 7:32 

Deploy B09 SIO 1 T40 35 0.11 2.55 3.0 1/29/12 10:05 

Deploy S11 WHOI 1 1 35 0.13 3.07 3.1 1/29/12 13:09 

Deploy B02 SIO 1 T240 35 0.11 2.55 3.2 1/29/12 15:42 

Deploy S12 WHOI 1 1 35 0.13 3.07 3.4 1/29/12 18:47 

Deploy S13 WHOI 1 1 20 0.10 2.30 3.5 1/29/12 21:05 

Deploy S14 SIO 1 20 0.06 1.53 3.5 1/29/12 22:37 

Deploy S15 SIO 1 20 0.06 1.53 3.6 1/30/12 0:08 

Deploy E12 SIO 1 45 0.12 2.81 3.7 1/30/12 2:57 

Deploy B01 SIO 1 T240 35 0.11 2.55 3.8 1/30/12 5:30 

Deploy E11 SIO 1 52 0.13 3.17 3.9 1/30/12 8:41 

Deploy S16 WHOI 1 20 0.06 1.53 4.0 1/30/12 10:12 

Deploy S17 WHOI 1 20 0.06 1.53 4.1 1/30/12 11:44 

Deploy S18 WHOI 1 1 20 0.10 2.30 4.2 1/30/12 14:02 

Deploy S19 WHOI 1 1 20 0.10 2.30 4.3 1/30/12 16:20 

Deploy B10 SIO 1 T240 30 0.10 2.29 4.4 1/30/12 18:38 

Deploy E09 SIO 1 39 0.10 2.51 4.5 1/30/12 21:08 

Deploy E08 SIO 1 20 0.06 1.53 4.5 1/30/12 22:40 

Deploy E07 SIO 1 20 0.06 1.53 4.6 1/31/12 0:12 

Deploy L05 WHOI 1 1 48 0.16 3.74 4.7 1/31/12 3:56 

Deploy E06 WHOI 1 50 0.13 3.07 4.9 1/31/12 7:01 

Deploy E05 SIO 1 20 0.06 1.53 4.9 1/31/12 8:32 

Deploy E04 SIO 1 20 0.06 1.53 5.0 1/31/12 10:04 

Deploy B11 SIO 1 T240 30 0.10 2.29 5.1 1/31/12 12:22 

Deploy N20 SIO 1 44 0.12 2.76 5.2 1/31/12 15:07 

Deploy N19 WHOI 1 20 0.06 0.03 5.3 1/31/12 16:39 

Deploy N18 WHOI 1 20 0.06 0.03 5.3 1/31/12 18:11 

Deploy B20 LDEO 1 88 0.22 5.28 5.6 1/31/12 23:27 

Deploy E01 SIO 1 35 0.10 2.30 5.7 2/1/12 1:45 

Deploy E02 SIO 1 20 0.06 1.53 5.7 2/1/12 3:17 

Deploy E03 SIO 1 20 0.06 1.53 5.8 2/1/12 4:49 

Deploy N16 SIO 1 20 0.06 1.53 5.8 2/1/12 6:20 

Deploy N15 WHOI 1 1 20 0.10 2.30 5.9 2/1/12 8:39 

Deploy N14 WHOI 1 1 20 0.10 2.30 6.0 2/1/12 10:57 

Deploy N13 WHOI 1 1 20 0.10 2.30 6.1 2/1/12 13:15 

Deploy B12 SIO 1 T240 26 0.09 2.09 6.2 2/1/12 15:20 

Deploy B08 LDEO 1 50 0.14 3.32 6.4 2/1/12 18:39 

Deploy L03 LDEO 1 1 1-yr 45 0.15 3.59 6.5 2/1/12 22:15 


Deploy L02 SIO 1 20 0.06 1.53 6.7 2/2/12 2:04 

Deploy W08 SIO 1 57 0.14 3.43 6.8 2/2/12 5:30 


Deploy W07 SIO 1 20 0.06 1.53 6.9 2/2/12 8:39 

Deploy W06 SIO 1 20 0.06 1.53 7.0 2/2/12 10:11 

Deploy L06 WHOI 1 36 0.10 2.35 7.1 2/2/12 12:32 

Deploy W05 WHOI 1 43 0.11 2.71 7.2 2/2/12 15:15 

Deploy N01 SIO 1 61 0.15 3.64 7.4 2/2/12 18:53 

Deploy N02 SIO 1 20 0.06 1.53 7.4 2/2/12 20:25 

Deploy B14 LDEO 1 24 0.08 1.98 7.5 2/2/12 22:24 

Deploy N03 WHOI 1 15 0.05 1.27 7.6 2/2/12 23:40 

Deploy N04 SIO 1 20 0.06 1.53 7.6 2/3/12 1:12 

Deploy N05 SIO 1 20 0.06 1.53 7.7 2/3/12 2:43 

Deploy N06 SIO 1 20 0.06 1.53 7.8 2/3/12 4:15 


Deploy N07 SIO 1 co-loc w B13 0 0.02 0.50 7.9 2/3/12 6:32 

Deploy N08 WHOI 1 1 20 0.10 2.30 8.0 2/3/12 8:50 

Deploy N09 LDEO 1 1 1-yr 20 0.10 2.30 8.0 2/3/12 11:08 

Deploy N10 WHOI 1 1 20 0.10 2.30 8.1 2/3/12 13:26 

Deploy N11 LDEO 1 1 1-yr 20 0.10 2.30 8.2 2/3/12 15:45 

Deploy N12 WHOI 1 1 20 0.10 2.30 8.3 2/3/12 18:03 

Deploy B19 SIO 1 T40 28 0.09 2.19 8.4 2/3/12 20:14 

Deploy B18 SIO 1 T240 49 0.14 3.27 8.6 2/3/12 23:30 

Deploy L08 WHOI 1 1 35 0.13 3.07 8.7 2/4/12 2:35 

Deploy B17 LDEO 1 33 0.10 2.45 8.8 2/4/12 5:02 

Deploy B16 SIO 1 T sensor 41 0.12 2.86 8.9 2/4/12 7:53 

Deploy L07 SIO 1 20 0.06 1.53 9.0 2/4/12 9:25 

Deploy B15 LDEO 1 68 0.18 4.25 9.2 2/4/12 13:40 

Deploy W01 WHOI 1 20 0.06 1.53 9.2 2/4/12 15:11 

Deploy W02 WHOI 1 20 0.06 1.53 9.3 2/4/12 16:43 

Deploy W03 SIO 1 20 0.06 1.53 9.3 2/4/12 18:15 

Contingency 0.00 0.00 9.3 2/4/12 18:15 

20 65 21 2,434 

Transit to Guam from W03 570 1.22 29.31 10.6 2/5/12 23:33 

Locked recovery contingency, weather 2.00 48.00 12.6 2/7/12 23:33 

Locked contingency, instrument problems 1.00 24.00 13.6 2/8/12 23:33 

Contingency 0.35 8.43 13.9 2/9/12 8:00 

13.92 

1 UNOLS day at the dock 1.00 2/9/12 8:00 

Total ship days needed 14.92 

Transit days 2.23 

Science days 12.68 

SP OBS totals = 32 SIO, 28 WHOI

Number of Instruments per deployment: 

OBSIP request web 

form: 

www.obsip.org 

OBSIP Instrument Request Form 

Date of Request: 

1. PROPOSAL INFORMATION 

Project Name (short): 

Lead PI Name: (should be 

consistent with UNOLS 

request) 

Institution: 

Address: 

Telephone: 

Fax: 

Email: 

Co-PI's: 

OBSIP Instrument Use Policies and Procedures 

Name: 

Institution (abbr): 

Need to specify: 

• Number & type of instruments 

(ie short period, broadband) 

• Number of deployments (ac=ve source) 

• Dura=on of deployment 

• Probable ports and dura=on of cruises 

• Water depths 

Full NSF Proposal Title: 

Short Description of the Project with emphasis on logistics and objectives of field 

work: 

Funding Agency: 

Submission Deadline: 

Special Program (e.g. 

RIDGE, MARGINS): 

Program Manager: 

2. INSTRUMENT REQUIREMENTS 

Type of Instrument Required: Short period 

Long period 

*If Other, Explain: 

Sampling Rate 

(samples/sec): 

Detailed deployment information 

Total Number of 

Deployments: 

Total Number of Instruments: 

DPG 

Other*

Informa=onal 

OBSIP Budget 

No. 0808 

OBSIP 

U.S. National Ocean Bottom Seismic Instrumentation Pool 

This is an informational budget provided to prospective users of instruments in the U.S. National Ocean Bottom 

Seismic Instrumentation Pool. The institutional instrument contributors (IICs) to the National Pool will provide 

complete engineering and technical support for OBS operations at sea. The cost of providing this support (e.g., 

instrument charges, personnel support, shipping and travel) will be funded directly through the Pool; these costs do 

not need to be included in individual science proposals. NSF does, however, require PIs to provide an informational 

budget estimating these costs in any proposal requesting OBSIP instruments. For more information on OBSIP, see 

http://www.obsip.org. 

Project title: 

Mantle serpentinization and water cycling throught the Mariana trench and forearc 

Principal Investigator(s): 

Funding Agency: 

Douglas Wiens, Dan Lizarralde 

NSF-OCE 

• A:ached to your proposal as a suppor=ng 

document 

• Provides an es=mate of the OBS costs of 

your proposal 

Submission deadline: 

Instruments: 

Date of prop. experiment: 

Logistics: 

Ports: 

65 SP OBS 4-component; 

20 BBOBS 4-component; 

85 deployments of 85 instruments 

The following is an estimate of the cost of supporting the OBS operations requested in this proposal. These costs 

are subject to change depending on the scheduling of this project, the length and ports of the deployment and 

recovery legs, and the OBSIP institution that supports this project. A final budget for OBS support operations for 

this project will be negotiated as part of the annual cooperative agreement between NSF and the Pool IICs. 

OBS Instrument drop charge: 4,342 per instrument* 

(includes batteries, deployment and, if applicable, redeployment costs) 

OBS engineering and technical support cost: 

(on shore and at sea) 

Shipping: 

Travel: 

July 1, 2008 

May 2010-May 2011 

Leg one, 44 days (R/V Langseth); Leg two, 14 days (medium R/V) 

Guam-Saipan; Saipan-Saipan 

369,077 

396,432 

53,920 

33,830 

Estimated total: 

$853,259 

* Varies from proposal to proposal based on the mix of instrument types and deployment lengths 

John Collins 

Chair, OBSIP Management Committee 

February 5, 2008

UNOLS ship request 

form 

www.unols.org 

Remaining 

Need to fill out ship request form and a:ach 

to your proposal as a suppor=ng document 

Informa=on needed: 

Size of ship (global, intermediate, etc) 

Number of science days needed, based on: 

# of OBSs 

depth of water (formulas in OBSIP docs) 

acous=c survey? 

transit =mes between sites 

con=ngency =me (for weather, failures) 

Likely ports and transit days to/from area 

Special equipment needed: 

mul=beam bathymetry 

MCS equipment 

airguns 

Characters: 500 

PI: Douglas Wiens, WUSTL Select PI * 

Remaining Characters: 300 

Washington University 

INSTITUTION: 1 Brookings Drive 

Select Institution * 

St. Louis, MO 63130 USA 




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Pre-‐cruise planning 

• Amount of pre-‐cruise planning depends on whether you are chief 

scien=st of the cruise 

• Assuming you are Chief Scien=st, you will need to submit a cruise 

plan to the ship operator (SIO, WHOI, etc) that: 

– Details all the objec=ves of the cruise (including how to spend 

“con=ngency =me”) 

– Gives a cruise track, with waypoints (need exact coordinates for OBS 

drops) 

– Provides a =meline for cruise opera=ons 

– Lists the scien=fic party (including the names of OBSIP techs) 

• You may also need to have conference calls or mee=ngs with the 

ship operator regarding the details of the cruise 

• As chief scien=st you are responsible for organizing the scien=fic 

party, and all the scien=fic decisions on ship opera=ons

OBS drop coordinates 

• You need to chose the exact OBS drop site coordinates 

• For broadband OBSs, if good bathymetry is available: 

-‐ Need to find rela=vely flat sites 

-‐ Far from hazards such as mudslides, volcanoes 

• If bathymetry is not available, bathymetry should be 

checked during the deployment cruise 

-‐ OBSs may drim as much as 500 m during descent 

-‐ Exact posi=on on the seafloor needs to be 

determined by acous=c ranging or airguns 

What you want 

to avoid 

Example of si=ng OBS on seamount

Deployment Cruise 

• If you are chief scien=st you will be responsible for represen=ng the science party 

and OBSIP in cruise decision making. For example, if weather causes changes in 

the cruise plan. 

• OBSIP provides essen=al technicians but normally several addi=onal people are 

required in support roles (ie grad students, etc) 

• Support du=es typically involve: 

– Monitoring data logging during transits 

– monitoring bathymetry at drop sites 

– logging instrument drop coordinates (backup) 

– assis=ng with instrument prepara=on 

– manning tag lines during deployment/recoveries 

– helping with deck opera=ons, tying down equipment 

• The OBSIP technicians normally take responsibility for planning the layout of 

equipment on the deck and planning deck opera=ons. 

• Communica=on for deck opera=ons generally goes through the “research 

technician” provided by the ship operator to the bridge. 

• Assuming things go well, you may need to decide how to use “con=ngency” =me. 

Ac=vi=es may include bathymetric surveying, magne=c/gravity data logging, 

dredging/sampling

Recovery Cruise 

• Recovery cruise tasks are fairly similar to 

deployment cruise 

• Need to allocate =me based on the depth and 

rise rate of the OBSs 

• Need con=ngency =me to allow for delays in 

releasing from the bo:om 

• Science party should assist in loca=ng the OBS 

once it reaches the surface, as well as tagging, 

etc

Data handling 

• The OBSIP is responsible for organizing the data, =me 

correc=ng, and basic Q/C 

• OBSIP will usually provide you with a “raw” dataset in 

miniseed (or SEGY?) format when leaving the ship 

• OBSIP will submit the data to the IRIS-‐DMS 1-‐12 months 

later and provide you with the final Q/C’ed dataset 

• I like to keep my own spreadsheet with OBS loca=ons and 

known problems as a backup. 

• There is no be:er Q/C than doing research with the data. 

The science group should also track problems and 

communicate with OBSIP if problems are discovered.

Data analysis and Results 

• Most techniques widely used for land broadband seismic 

experiments can be directly applied to OBS data 

• This includes surface and body wave tomography, a:enua=on 

tomography, noise correla=on analysis, shear wave spli{ng, 

seismicity and seismic source studies. 

• One excep=on is receiver func=ons – the P reverbera=on in 

the water layer omen arrives in the early part of the coda and 

can obscure P-‐S conversions used in RF analysis 

• There has been some success in studying the 410 and 660 km 

discon=nui=es with LP receiver func=ons.

Structure of a mid-‐ocean Ridge – the 

MELT experiment 

S velocity structure from regional Love waves 

Summary Cartoon 

Dunn & Forsyth [2003] 

Forsyth et al. [1998]

P velocity structure of the Mariana Arc/Backarc 

= maximum 

anomaly 

Barklage et al., in prep 

• Strong slow velocity anomalies beneath the arc and backarc spreading center (~ 7.3 km/s) 

• Volcanic arc anomaly is deeper than the backarc anomaly, and depths are similar to 

final magma equilibration depths from Si & Mg thermobarometry: 

21-34 km for the backarc spreading center 

34-87 km for the volcanic arc [Kelley et al., 2010]

Shear velocity structure of the Lau Basin 

from Rayleigh wave phase veloci=es 

S. Wei et al, in prep

Cascadia Ini=a=ve – 4 year community 

deployment with open data 

Mul=-‐scale array with several 

components 

• Regional/Transportable array 

– Plate scale imaging 

• Monitoring array 

– Nominal sta=on spacing of 35 km along the 

thrust 

• 3 focused experiments 

– Grays Harbor (2011/2013) 

– Mendocino Triple Junc=on (2012) 

– Central Oregon segment boundary (2014) 

• Deployment cruises lead by PI team 

(Doug Toomey lead PI) 

• Data available at IRIS DMC as soon as 

recovered and processed 

49˚N 

48˚N 

47˚N 

46˚N 

45˚N 

44˚N 

43˚N 

42˚N 

Cascadia Design 

meters 

−100 

−200 

−300 

−400 

41˚N 

40˚N 

131˚W 130˚W 129˚W 128˚W 127˚W 126˚W 125˚W 124˚W 123˚W 122˚W 

2011 Nov 28 05:02:59

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