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Characterizing the Calico Fault Damage Zone Using Seismic and Geodetic Data Elizabeth S. Cochran (University of California, Riverside), Yong-Gang Li (University of Southern California), Peter M. Shearer (Scripps Institution of Oceanography), Sylvain Barbot (Scripps Institution of Oceanography), Yuri Fialko (Scripps Institution of Oceanography), John E. Vidale (University of Washington) During earthquakes slip is often localized on preexisting faults, but it is not well understood how the structure of crustal faults may contribute to slip localization and energetics. Growing evidence suggests that the crust along active faults suffers anomalous strain and damage during large quakes. Seismic and geodetic data from the Calico fault in the eastern California shear zone reveal a wide zone of reduced seismic velocities and effective elastic moduli. Using seismic travel times, trapped waves, and interferometric Synthetic Aperture Radar observations, we document seismic velocities reduced by 40 - 50% and shear moduli reduced by 65% compared to wallrock in a 1.5-km-wide zone along the Calico fault [Cochran et al., 2009]. Observed velocity reductions likely represent the cumulative mechanical damage from past earthquake ruptures. No large earthquake has broken the Calico fault in historic time, implying that fault damage persists for hundreds or perhaps thousands of years. These findings indicate that faults can affect rock properties at substantial distances from primary fault slip surfaces, and throughout much of the seismogenic zone, a result with implications for the portion of energy expended during rupture to drive cracking and yielding of rock and development of fault systems. References Cochran, E.S., Li, Y.-G., Shearer, P.M., Barbot, S., Fialko, Y., and Vidale, J.E., Seismic and Geodetic Evidence for Extensive, Long-Lived, Fault Damage Zones, Geology, 37(4), 315-318, 2009. Acknowledgements: This research was supported by NSF (EAR-0439947) and SCEC (contribution number 1185). Figure 1. (A) A shaded relief map of the Mojave Desert region. Regional faults are shown by dashed gray lines and the Landers and Hector Mine ruptures are shown by solid gray lines. Light and dark blue circles indicate local earthquakes used in the fault zone trapped wave and travel-time analyses, respectively. Light blue circles with a dark blue outline were used in both analyses. Red stars denote shots. Black triangles and circles show seismic stations. The gray square outlines the region in Figure 1B. (B) High-pass-filtered coseismic interferogram from the 16 October 1999 Hector Mine earthquake that spans the time period from 13 January 1999 – 20 October 1999 (after Fialko et al., 2002). Colors denote variations in the line of sight (LOS) displacements. Black triangles and red circles are intermediate-period and short-period seismic stations. (C) Best fit model of P-wave low velocity zone with a 40% reduction in velocity estimated from seismic and geodetic data. II-110 | 2010 IRIS Core Programs Proposal | Volume II | Fault Structure
Temporal Variations in Crustal Scattering Structure Near Parkfield, California, Using Receiver Functions Pascal Audet (University of California Berkeley) We investigate temporal variations in teleseismic receiver functions using 11 yrs of data at station PKD near Parkfield, California, by stacking power spectral density (PSD) functions within 12-month windows. We find that PSD levels for both radial and transverse components drop by ~5 dB following the 2003 San Simeon (M 6.5) earthquake, with a persistent reduction in background levels of ~2 dB, relative to the pre-2003 levels, after the 2004 Parkfield (M 6) earthquake, corresponding to an estimated decrease in shear-wave velocity of ~0:12 and ~0:06 km/sec, respectively, or equivalent negative changes in Poisson’s ratio of ~0:02 and ~0:01. Our results suggest that the perturbation originates at middle to lower crustal levels, possibly caused by the redistribution of crustal pore fluids, consistent with increased and sustained tremor activity near Parkfield following both earthquakes. This study shows that we can resolve temporal variations in crustal scattering structure near a major seismogenic fault using the receiver function method. References Audet, P., 2010. Temporal variations in crustal velocity structure near Parkfield, California, using receiver functions, Bull. Seismol. Soc. Amer., 100. Ozacar, A. A., and G. Zandt (2009). Crustal structure and seismic anisotropy near the San Andreas fault at Parkfield, California, Geophys. J. Int., 178, 1098–1104 Acknowledgements: This work was supported by the Miller Institute for Basic Research in Science (UC Berkeley). Data was made available by the Northern California Earthquake Data Center (NCEDC). Moho piercing points of receiver functions grouped in two back-azimuth ranges of incoming wave fields (black, 0–200°; gray, 225–360°) at station PKD near Parkfield, California, with respect to study region (inset, major faults in gray). This grouping also corresponds to sampled volumes exhibiting different contrasts in VP/VS of the upper to middle crust with lower values in the west (Ozacar and Zandt, 2009) . San Andreas Fault is indicated by the gray lines near Parkfield. Stars in inset indicate the location of the 2003 San Simeon (SS) and 2004 Parkfield (PK) earthquakes. Temporal variations in receiver functions at station PKD for back azimuths 0–200°. Top panels show power spectral density of receiver functions binned within 95% overlapping, 12-month windows for (a) radial and (b) transverse components. (c) Corresponding variations in total power (black line, radial; gray line, transverse). Distribution of the 284 events with respect to (d) back azimuth and (e) slowness of incoming wavefields is presented in bottom panels. The thick vertical lines in (a) and (b) indicate times of the San Simeon (2003) and Parkfield (2004) earthquakes. 2010 IRIS Core Programs Proposal | Volume II | Fault Structure | II-111
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volume ii - accomplishments Facilit
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volume ii - accomplishments Facilit
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CONTENTS Introduction..............
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Non-Volcanic Tremor along the Oaxac
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Detecting the Limit of Slab Break-o
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Lower Mantle, Core-Mantle Boundary
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• Non-Earthquake Seismic Sources
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acoustics community by permitting a
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Near-Surface Environments - Hazards
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Why Do Faults Slip? Emily Brodsky (
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Another probe of fault evolution is
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to provide a best match with the Gl
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tectonic disruption and mass accumu
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W3 ∆ 5 . A number of intriguing r
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thermal and compositional effects r
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Towards a Global School Seismic Net
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On-Line Seismology Curriculum for U
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Teachers on the Leading Edge: Earth
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USArray Education and Outreach in S
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From an IRIS Lecture Tour to a Gene
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Explorer Series Robert Bartolotta (
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Workshop “Earth System Science fo
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The IRIS Internship Cycle: From Int
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Community-Outreach Efforts in Data
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Site Reconnaissance for Earthscope
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jAmaseis: Seismology Software Meeti
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Near Real-Time Simulations of Globa
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FuncLab: A MATLAB Interactive Toolb
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Five Years of Distributing the Seis
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IRIS DMS Data Products, Beyond Raw
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Local Earthquakes in the Dallas-Ft.
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Epicentral Location Based on Raylei
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Analysis of Spatial and Temporal Se
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Exceptional Ground Motions from the
Page 71 and 72: The 2010 Mw7.2 El Mayor-Cucapah Ear
Page 73 and 74: Effects of Kinematic Constraints on
Page 75 and 76: Imaging of the Source Properties of
Page 77 and 78: Teleseismic Inversion for Rupture P
Page 79 and 80: The Global Aftershocks of the 2004
Page 81 and 82: The 17 July 2006 Java Tsunami Earth
Page 83 and 84: Seismic Cycles on Oceanic Transform
Page 85 and 86: Migration of Early Aftershocks Foll
Page 87 and 88: Apparent Stress Variations at the O
Page 89 and 90: Automated Identification of Telesei
Page 91 and 92: Evaluating Ground Motion Prediction
Page 93 and 94: Tremor Monitoring Aaron Wech (Unive
Page 95 and 96: Slow Slip and Tremor in the Norther
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Page 99 and 100: Intimate Details of Tremor Observed
Page 101 and 102: Global Search of Triggered Tremor a
Page 103 and 104: Slab Morphology in the Cascadia For
Page 105 and 106: Source Analysis of the Memorial Day
Page 107 and 108: Iceberg Tremor and Ocean Signals Ob
Page 109 and 110: Elucidating the Stick-Slip Nature o
Page 111 and 112: Probing the Atmosphere and Atmosphe
Page 113 and 114: Volcanic Plume Height Measured by S
Page 115 and 116: Eruption Dynamics at Mount St. Hele
Page 117 and 118: A Search for the Lunar Core Using A
Page 119 and 120: Seismic Imaging of the Mt. Rose Fau
Page 121: Structure of the California Coast R
Page 125 and 126: High-Resolution Locations of Trigge
Page 127 and 128: Adjoint Tomography of the Southern
Page 129 and 130: Crustal Structure of the High Lava
Page 131 and 132: Controlled Source Seismic Experimen
Page 133 and 134: Structural Interpretations Based on
Page 135 and 136: Optimized Velocities and Prestack D
Page 137 and 138: 40 Crustal Structure beneath the Hi
Page 139 and 140: Controlled-Source Seismic Investiga
Page 141 and 142: Northward Thinning of Tibetan Crust
Page 143 and 144: An Integrated Analysis of an Ancien
Page 145 and 146: Crustal Velocity Structure of Turke
Page 147 and 148: Ambient Noise Tomography of the Pam
Page 149 and 150: Ambient Noise Monitoring of Seismic
Page 151 and 152: Mushy Magma beneath Yellowstone Ris
Page 153 and 154: Imaging the Seattle Basin to Improv
Page 155 and 156: Developing a Database of ENA Ground
Page 157 and 158: Lithospheric Layering in the North
Page 159 and 160: eflective zones on depthmigrated se
Page 161 and 162: FischerFig05.pdf 1 2/8/10 12:31 PM
Page 163 and 164: S-Velocity Structure of Cratons, fr
Page 165 and 166: Seismic Structure of the Crust and
Page 167 and 168: Subducted Oceanic Asthenosphere and
Page 169 and 170: Detecting the Limit of Slab Break-o
Page 171 and 172: Pn Tomography of the Western United
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3-D Isotropic Shear Velocity Model
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Seismic Anisotropy Associated with
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Anisotropy in the Great Basin from
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Source-Side Shear Wave Splitting an
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S-Velocity Structure of the Upper M
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Velocity Structure of the Western U
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Segmented African Lithosphere benea
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Imaging the Mantle Wedge in the Cen
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A Slab Remnant beneath the Gulf of
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Imaging the Southern Alaska Subduct
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Opposing Slabs under Northern South
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Effect of Prior Petrological Constr
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Global Azimuthal Seismic Anisotropy
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The Stratification of Seismic Azimu
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Upper Mantle Anisotropy beneath the
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The Teleseismic Signature of Fossil
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Seismic Anisotropy under Central Al
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Stress-Induced Upper Crustal Anisot
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Tau-p Depropagation of Five Regiona
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Mapping the Upper Mantle with the S
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Upper Mantle Structure of Southern
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The Africa-Europe Plate Boundary in
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The Isabella Anomaly Imaged by Eart
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Tomographic Image of the Crust and
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Small-Scale Mantle Heterogeneity an
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Mantle Heterogeneity West and East
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New Geophysical Insight into the Or
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The Plume-slab Interaction beneath
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Imaging the Shear Wave Velocity "Pl
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Slab Fragmentation and Edge Flow: I
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Mantle Shear-Wave Velocity Structur
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Discordant Contrasts of P- and S-Wa
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Upper Mantle Discontinuity Topograp
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Edge-Driven Convection beneath the
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Imaging Attenuation in the Upper Ma
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Three-Dimensional Electrical Conduc
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Core-Mantle Boundary Heat Flow Thor
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Constraints on Lowermost Mantle Ani
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Localized Double-Array Stacking Ana
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Waveform Modeling of D" Discontinui
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Absence of Ultra-Low Velocity Zones
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Moving Seismic Tomography Beyond Fa
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A Three-Dimensional Radially Anisot
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The Importance of Crustal Correctio
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Slabs Do Not Go Gentle Karin Sigloc
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Localized Temporal Change of the Ea
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Core Structure Reexamined Using New
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Large Variations in Travel Times of
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Observations of Antipodal PKIIKP Wa
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Regional Variation of Inner Core An
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Wide-Scale Detection of Earthquake
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