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Attenuation and Anisotropy in the Northern Apennines, Italy J. Park (Yale University), D. Piccinini (INGV), I. Bianchi (INGV), M. Di Bona (INGV), F. P. Lucente (INGV), N. Piana Agostinetti (INGV), V. Levin (Rutgers University) The Northern Apennines of Italy is marked by continental convergence and a downgoing slab derived from the Adriatic microplate. Seismicity is sparse, shallow, and lacks historical M>7.5 shallow thrust events. Has subduction ceased? Geodesy indicates nearzero present-day convergence, and fission-track thermochronology suggests that vertical uplift has superseded fold-and-thrust tectonics since 5-10 Ma in a large segment of the orogen. The RETREAT project (REtreating-TRench Extension and Accretion Tectonics) explored this region with broadband seismometers from the IRIS PASSCAL program, the Czech Academy of Sciences and the Istituto Nazionale de Geofisica e Vulcanologia (INGV). Attenuation estimates from both S and P waves reveal high attenuation on the "backarc" side of the Apennines orogen (Figure 1), near coastal geothermal areas but extending inland. Pleistocene volcanism is found here, but there is no present-day subduction-arc activity. A crude inversion of t-star (Δt*) suggests comparable Q values (
Stress-Induced Upper Crustal Anisotropy in Southern California Zhaohui Yang (University of Colorado at Boulder), Anne Sheehan (University of Colorado at Boulder) We use an automated method to analyze shear-wave splitting from local earthquakes recorded by the Southern California Seismic Network (SCSN) between 2000 and 2005. The observed fast directions of upper-crustal anisotropy are mostly consistent with the direction of maximum horizontal compression σHmax, suggesting that anisotropy in the top 20 km of crust under southern California is stress-induced anisotropy. At some stations, fast directions are aligned with the trends of regional faulting and local alignment of anisotropic bedrock. Delay times range widely from 0.02 s to 0.15 s. These upper-crustal anisotropy observations, together with previous studies of SKS shear-wave splitting and receiver functions, show different mechanisms of anisotropy at different depths under southern California. Anisotropy in the upper crust and upper mantle appears to be in response to the current horizontal maximum compression σHmax, whereas lower crustal anisotropy may be caused by the anisotropic schist accreted during the subduction of Farallon plate, which is frozen in the lower crust. We also explore possible temporal variations in upper-crustal anisotropy associated with pre-earthquake stress changes or stress changes excited by surface waves of great earthquakes. However, we do not observe any clear temporal variations in fast directions or time delays. References Yang, Z., A. F. Sheehan, and P. Shearer, Stress-Induced Upper Crustal Anisotropy in Southern California, submitted to J. Geophys. Res., 2010. Gripp, A.E., and R.G. Gordon (1990), Current Plate Velocities Relative to the Hotspots Incorporating the NUVEL-1 Global Plate Motion Model, Geophysical Research Letters, 17(8), 1109-1112. McQuarrie, N., and B.P. Wernicke (2005), An animated tectonic reconstruction of southwestern North America since 36 Ma, Geosphere, 1(3), 147-172. Porter, R., G. Zandt, and N. McQuarrie (2010), Pervasive lower crustal seismic anisotropy in southenr California: Evidence for underplated schists, Submitted. Acknowledgements: The data used in this study were made available by the Southern California Seismic Network, and we are grateful to E. Hauksson for his assistance in creating a waveform database. We thank J. Polet for providing a digital table of his Southern California SKS measurements, R. Porter for sharing a preprint of his Southern California receiver function work, and M. Savage for her comments. The figures were made using GMT software by P. Wessel and W. Smith. AFS gratefully acknowledges a Green Foundation Fellowship that supported her sabbatical at IGPP/SIO. This work is supported by SCEC project 08129 and NSF EAR grant 0409835, and by U.S. Geological Survey award number G09AP00052. Map showing average fast directions of upper-crustal anisotropy (solid bars), SKS shear-wave splitting anisotropy (blue bars), and stress vectors (gray bars). The inset rose diagram summarizes the trends of anisotropies from three different depths in the area of the map: Top 20 km of crust (black), the fast directions are consistent with the direction of current maximum horizontal compression (gray arrows); and upper mantle, SKS shearwave splitting show a preferred fast direction orienting E-W (blue bars). The orange arrows are Farallon plate subduction directions during 59-42 Ma [McQuarrie and Wernicke, 2005]. The trends of anisotropy in the lower crust (below 20 km), after rotation back to 36 Ma [Porter et al., 2010], are consistent with the Farallon subduction directions during 59-42 Ma. The black arrow indicates the absolute plate motion (APM) of the North American plate [Gripp and Gordon, 1990]. 2010 IRIS Core Programs Proposal | Volume II | Upper Mantle Structure and Dynamics | II-195
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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
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The 2010 Mw7.2 El Mayor-Cucapah Ear
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Effects of Kinematic Constraints on
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Imaging of the Source Properties of
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Teleseismic Inversion for Rupture P
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The Global Aftershocks of the 2004
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The 17 July 2006 Java Tsunami Earth
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Seismic Cycles on Oceanic Transform
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Migration of Early Aftershocks Foll
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Apparent Stress Variations at the O
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Automated Identification of Telesei
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Evaluating Ground Motion Prediction
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Tremor Monitoring Aaron Wech (Unive
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Slow Slip and Tremor in the Norther
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0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2
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Intimate Details of Tremor Observed
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Global Search of Triggered Tremor a
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Slab Morphology in the Cascadia For
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Source Analysis of the Memorial Day
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Iceberg Tremor and Ocean Signals Ob
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Elucidating the Stick-Slip Nature o
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Probing the Atmosphere and Atmosphe
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Volcanic Plume Height Measured by S
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Eruption Dynamics at Mount St. Hele
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A Search for the Lunar Core Using A
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Seismic Imaging of the Mt. Rose Fau
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Structure of the California Coast R
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Temporal Variations in Crustal Scat
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High-Resolution Locations of Trigge
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Adjoint Tomography of the Southern
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Crustal Structure of the High Lava
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Controlled Source Seismic Experimen
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Structural Interpretations Based on
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Optimized Velocities and Prestack D
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40 Crustal Structure beneath the Hi
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Controlled-Source Seismic Investiga
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Northward Thinning of Tibetan Crust
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An Integrated Analysis of an Ancien
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Crustal Velocity Structure of Turke
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Ambient Noise Tomography of the Pam
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Ambient Noise Monitoring of Seismic
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Mushy Magma beneath Yellowstone Ris
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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
Page 173 and 174: 3-D Isotropic Shear Velocity Model
Page 175 and 176: Seismic Anisotropy Associated with
Page 177 and 178: Anisotropy in the Great Basin from
Page 179 and 180: Source-Side Shear Wave Splitting an
Page 181 and 182: S-Velocity Structure of the Upper M
Page 183 and 184: Velocity Structure of the Western U
Page 185 and 186: Segmented African Lithosphere benea
Page 187 and 188: Imaging the Mantle Wedge in the Cen
Page 189 and 190: A Slab Remnant beneath the Gulf of
Page 191 and 192: Imaging the Southern Alaska Subduct
Page 193 and 194: Opposing Slabs under Northern South
Page 195 and 196: Effect of Prior Petrological Constr
Page 197 and 198: Global Azimuthal Seismic Anisotropy
Page 199 and 200: The Stratification of Seismic Azimu
Page 201 and 202: Upper Mantle Anisotropy beneath the
Page 203 and 204: The Teleseismic Signature of Fossil
Page 205: Seismic Anisotropy under Central Al
Page 209 and 210: Tau-p Depropagation of Five Regiona
Page 211 and 212: Mapping the Upper Mantle with the S
Page 213 and 214: Upper Mantle Structure of Southern
Page 215 and 216: The Africa-Europe Plate Boundary in
Page 217 and 218: The Isabella Anomaly Imaged by Eart
Page 219 and 220: Tomographic Image of the Crust and
Page 221 and 222: Small-Scale Mantle Heterogeneity an
Page 223 and 224: Mantle Heterogeneity West and East
Page 225 and 226: New Geophysical Insight into the Or
Page 227 and 228: The Plume-slab Interaction beneath
Page 229 and 230: Imaging the Shear Wave Velocity "Pl
Page 231 and 232: Slab Fragmentation and Edge Flow: I
Page 233 and 234: Mantle Shear-Wave Velocity Structur
Page 235 and 236: Discordant Contrasts of P- and S-Wa
Page 237 and 238: Upper Mantle Discontinuity Topograp
Page 239 and 240: Edge-Driven Convection beneath the
Page 241 and 242: Imaging Attenuation in the Upper Ma
Page 243 and 244: Three-Dimensional Electrical Conduc
Page 245 and 246: Core-Mantle Boundary Heat Flow Thor
Page 247 and 248: Constraints on Lowermost Mantle Ani
Page 249 and 250: Localized Double-Array Stacking Ana
Page 251 and 252: Waveform Modeling of D" Discontinui
Page 253 and 254: Absence of Ultra-Low Velocity Zones
Page 255 and 256: 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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