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Deep Mantle Plumes and Convective Upwelling beneath the Pacific Ocean Nicholas Schmerr (Carnegie Institution of Washington), Edward Garnero (Arizona State University), Allen McNamara (Arizona State University) The 410 and 660 km discontinuities arise from solid-to-solid phase changes in the mineral olivine, and lateral variations in temperature and composition incurred by dynamical processes in the mantle produce topography on each boundary. To query discontinuity structure in the presence of mantle downwellings and upwellings, we use underside reflections of shear waves, a technique that requires the stacking of hundreds to thousands of seismograms. This method has flourished from the deployment of global and regional seismic arrays, whose data are freely available from the IRIS DMC. We collected a dataset of over 130,000 broadband seismograms that sample beneath the Pacific Ocean. In our study, we resolve the discontinuities to be relatively flat beneath most of the Pacific, except under subduction zones and volcanic hotspots. We find the phase boundaries are closer together beneath the Hawaiian hotspot, and also in a larger region of the south Pacific that is flanked by a number of volcanic hotspots. This region overlies the southern part of the large-scale low shear velocity province in the lowermost mantle, indicative of a large plume head or cluster of several plumes originating in the lowermost mantle and impinging upon the south Pacific 660 km discontinuity. This feature may be related to large volume volcanic eruptions, such as the Cretaceous Ontong Java Plateau flood basalts, which have been proposed to originate in the south Pacific. References Schmerr, N., et al. (2010), Deep mantle plumes and convective upwelling beneath the Pacific Ocean, Earth Planet. Sci. Lett., 294, 143-151. Acknowledgements: NSF Grants EAR-0711401, EAR-0453944, EAR-0510383, EAR-0456356 Topography maps for discontinuity depths and transition zone thickness in our Pacific study region. The depths are plotted relative to average values of 418 km, 656 km, and an average transition zone thickness of 242 km. II-224 | 2010 IRIS Core Programs Proposal | Volume II | Upper Mantle Structure and Dynamics
Upper Mantle Discontinuity Topography from Thermal and Chemical Heterogeneity Nicholas Schmerr (Carnegie Institution of Washington), Edward Garnero (Arizona State University) Utilizing high resolution stacks of precursors to the seismic phase SS, we investigated seismic discontinuities associated with mineralogical phase changes at approximately 410 and 660 kilometers deep within the Earth beneath South America and the surrounding oceans. We utilized a dataset of over 17,000 broadband seismograms collected from the IRIS DMC and EarthScope. Our maps of phase boundary topography revealed deep 410- and 660-km discontinuities in the down-dip direction of subduction, inconsistent with cold material at 410-km depth. We explored several mechanisms invoking chemical heterogeneity within the mantle transition zone to explain this feature. In some regions, we detected multiple reflections from the discontinuities, consistent with partial melt near 410-km depth and/or additional phase changes near 660-km depth. Thus, the origin of upper mantle heterogeneity has both chemical and thermal contributions, and is associated with deeply rooted tectonic processes. References Schmerr, N., and E. Garnero (2007), Upper mantle discontinuity topography from thermal and chemical heterogeneity, Science, 318(5850), 623-626. Acknowledgements: NSF Awards EAR-0453944 and EAR-0711401 A cross section explaining our results, whereby iron is removed by melting in the mantle wedge and the Mg-enriched residue is swept into the transition zone along with the subducting lithosphere. This increases the pressure at which olivine transforms into wadsleyite, deepening the 410 km boundary. 2010 IRIS Core Programs Proposal | Volume II | Upper Mantle Structure and Dynamics | II-225
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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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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
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Developing a Database of ENA Ground
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Lithospheric Layering in the North
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eflective zones on depthmigrated se
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FischerFig05.pdf 1 2/8/10 12:31 PM
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S-Velocity Structure of Cratons, fr
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Seismic Structure of the Crust and
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Subducted Oceanic Asthenosphere and
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Detecting the Limit of Slab Break-o
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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
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 and 206: Seismic Anisotropy under Central Al
Page 207 and 208: Stress-Induced Upper Crustal Anisot
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: Discordant Contrasts of P- and S-Wa
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
Page 257 and 258: A Three-Dimensional Radially Anisot
Page 259 and 260: The Importance of Crustal Correctio
Page 261 and 262: Slabs Do Not Go Gentle Karin Sigloc
Page 263 and 264: Localized Temporal Change of the Ea
Page 265 and 266: Core Structure Reexamined Using New
Page 267 and 268: Large Variations in Travel Times of
Page 269 and 270: Observations of Antipodal PKIIKP Wa
Page 271 and 272: Regional Variation of Inner Core An
Page 273: Wide-Scale Detection of Earthquake
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