A5080033015- earthquake and tectonic studies
- Geological and Geochemical Analysis
- High-pressure geophysics and materials
- Seismic Waves and Analysis
- Seismic Imaging and Inversion Techniques
- Cryospheric studies and observations
- Seismology and Earthquake Studies
- Geological and Geophysical Studies
- Landslides and related hazards
- Geology and Paleoclimatology Research
- Methane Hydrates and Related Phenomena
- Winter Sports Injuries and Performance
- Hydrocarbon exploration and reservoir analysis
- Earthquake Detection and Analysis
- Geological Studies and Exploration
- Geophysics and Sensor Technology
- Arctic and Antarctic ice dynamics
- Geological and Tectonic Studies in Latin America
- Geological formations and processes
- Drilling and Well Engineering
- Polar Research and Ecology
- Reservoir Engineering and Simulation Methods
- Geophysics and Gravity Measurements
- Planetary Science and Exploration
- Astro and Planetary Science
Washington University in St. Louis
2016-2025
Planetary Science Institute
1987-2024
British Antarctic Survey
2023
Macquarie University
2021
University of Washington
2006-2015
St. Hedwig-Krankenhaus
2014
University of Southern California
1997
Southern California Earthquake Center
1997
Scripps Institution of Oceanography
1997
University of California, San Diego
1997
We have determined depths for 16 oceanic intraplate earthquakes using body wave modeling. A data set composed of these and 11 other well‐constrained shows that the maximum depth seismicity deepens with increasing lithospheric age appears to be bounded by a 700°–800°C isotherm. The which occur is approximately equal flexural elastic thickness but much less than seismic from surface dispersion. faulting consistent predictions rapid weakening at high temperatures dry olivine rheologies...
The marine portion of the West Antarctic Ice Sheet (WAIS) in Amundsen Sea Embayment (ASE) accounts for one-fourth cryospheric contribution to global sea-level rise and is vulnerable catastrophic collapse. bedrock response ice mass loss, glacial isostatic adjustment (GIA), was thought occur on a time scale 10,000 years. We used new GPS measurements, which show rapid (41 millimeters per year) uplift ASE, estimate viscosity mantle underneath. found much lower (4 × 1018 pascal-second) than...
Abstract We estimate the upper mantle temperature of Antarctic Plate based on thermoelastic properties minerals and S velocities using a new 3‐D shear velocity model, AN1‐S. Crustal temperatures surface heat fluxes are then calculated from assuming steady state thermal conduction. The at top asthenosphere beneath oceanic region West Antarctica is higher than dry solidus, indicating presence melt. From values, we generate depth maps lithosphere‐asthenosphere boundary Curie isotherm. show that...
Seismic tomography revealed a low seismic velocity (-5%) and high Poisson's ratio (+6%) anomaly covering about 300 square kilometers at the hypocenter of 17 January 1995, magnitude 7.2, Kobe earthquake in Japan. This may be due to an overpressurized, fluid-filled, fractured rock matrix that contributed initiation earthquake.
Source parameter inversion of P and SH waveforms amplitudes for 20 shallow earthquakes using a singular value decomposition technique provides important constraints on the tectonics relative plate motions Scotia Sea region. The derived focal mechanisms show both thrust strike‐slip faulting along North Ridge normal South Ridge. Two south Tierra del Fuego indicate diffuse convergence Antarctic western margin plate. Earthquakes are consistent with active subduction back arc spreading Shetland...
Seismic tomography and wave form inversion revealed that very slow velocity anomalies (5 to 7 percent) beneath the active Lau spreading center extend 100-kilometer depth are connected moderately (2 4 in mantle wedge 400-kilometer depth. These results indicate geodynamic systems associated with back-arc related deep processes, such as convective circulation dehydration reactions subducting slab. The regions Tonga arc back separated at shallow levels but merge depths greater than 100...
Shear-wave splitting analysis of local events recorded on land and the ocean floor in Tonga arc Lau backarc indicate a complex pattern azimuthal anisotropy that cannot be explained by mantle flow coupled to downgoing plate. These observations suggest direction rotates from convergence-parallel Fiji plateau north-south beneath basin arc-parallel arc. results correlate with helium isotopes map Samoan plume into through an opening tear Pacific
Australia and India are conventionally thought to be contained in a single plate divided from an Arabian by the Owen Fracture Zone. We propose instead that motion along nearly aseismic Zone is negligible Arabia within Indo‐Arabian plate, Australian diffuse boundary. This boundary, which trends E‐W Central Indian Ridge near Chagos Bank Ninetyeast Ridge, north Sumatra Trench, zone of concentrated seismicity deformation heretofore characterized as “intraplate”. Plate inversions F‐ratio test...
We have conducted a systematic study of oceanic intraplate seismicity in the period 1964–1983 occurring lithosphere younger than 35 million years. Focal mechanisms determined for 26 events using first motions, P wave modeling and surface amplitude radiation patterns, along with 13 previously mechanisms, indicate diversity faulting styles stress orientations young lithosphere. There is no evidence worldwide transition from extension to compression at specific lithospheric age. Tensional axes...
The November 20, 1960, Peru, October 1963, Kurile and June 10, 1975, earthquakes are classified as tsunami based on anomalously large excitation relative to earthquake magnitude. Long‐period surface wave analysis indicates double‐couple (faulting) mechanisms for all three events rather than single‐force indicative of submarine landslides. have shallow depths (< 15 km) located near the trench axis seaward most other thrust zone beneath accretionary prism. Body waveform inversion very...
Abstract Since 2007/2008, seismographs were deployed in many new locations across much of Antarctica. Using the records from 122 broadband seismic stations, over 10,000 Rayleigh wave fundamental‐mode dispersion curves have been retrieved earthquake waveforms and ambient noise. processed data set, a 3‐D S ‐velocity model for Antarctic lithosphere was constructed using single‐step surface tomographic method, Moho depth map estimated model. derived crustal thicknesses, average ratio...
We have studied 40 earthquakes on seven major transforms along the Mid‐Atlantic Ridge. The majority show expected transform‐parallel strike‐slip motion steeply dipping fault planes. Some “anomalous” mechanisms, suggesting either unusually shallow dip or a component of dip‐slip motion, occur near ridge‐transform intersections. vertical tectonism suggested by transform morphology may thus be restricted to intersections where thermal contrast across is greatest and stress orientations can...
The Cameroon Volcanic Line (CVL) consists of a linear chain Tertiary to Recent, generally alkaline, volcanoes that do not exhibit an age progression. Here we study crustal structure beneath the CVL and adjacent regions in using 1-D shear wave velocity models obtained from joint inversion Rayleigh group velocities P-receiver functions for 32 broad-band seismic stations deployed between 2005 January 2007 February. We find (1) thickness (35–39 km) is similar Pan African Oubanguides Belt south...
Abstract The upper mantle and transition zone beneath Antarctica the surrounding oceans are among poorest‐imaged regions of Earth's interior. Over last 15 years, several large broadband regional seismic arrays have been deployed, as new permanent stations. Using data from 297 Antarctic 26 additional stations south ~40°S, we image structure using adjoint tomography. course 20 iterations, utilize phase observations three‐component seismograms containing P , S Rayleigh, Love waves, including...
P‐to‐S receiver functions (PRFs) from the Polar Earth Observing Network (POLENET) GPS and seismic leg of POLENET spanning West Antarctica Transantarctic Mountains deployment seismographic stations provide new estimates crustal thickness across Antarctica, including Antarctic Rift System (WARS), Marie Byrd Land (MBL) dome, (TAM) margin. We show that complications arising ice sheet multiples can be effectively managed further information concerning low‐velocity subglacial sediment may...
Abstract We construct a new seismic model for central and West Antarctica by jointly inverting Rayleigh wave phase group velocities along with P receiver functions. Ambient noise tomography exploiting data from more than 200 stations deployed over the past 18 years is used to velocity dispersion maps. Comparison between ambient maps those constructed using teleseismic earthquakes confirms accuracy of both results. These maps, together function waveforms, are 3‐D shear (Vs) crust uppermost...
Abstract The seismic velocity structure of Antarctica is important, both as a constraint on the tectonic history continent and for understanding solid Earth interactions with ice sheet. We use Rayleigh wave array analysis methods applied to teleseismic data from recent temporary broadband seismograph deployments image upper mantle central West Antarctica. Phase maps are determined using two–plane tomography method inverted shear Monte Carlo approach estimate three‐dimensional structure....
Abstract We summarize new observations of the deceleration and stick–slip motion Whillans Ice Stream (WIS), Antarctica. refine location large sticky spots that resist between slip events, locations which are controlled by patterns subglacial water flow. Our examination long-term velocity time series for ice stream reveals decadal-scale is not occurring at a steady rate, but varies sub-decadal timescale. This unsteady modulates temporal evolution broad (~50 km across) surface-elevation bulge...
Abstract The geothermal heat flux (GHF) is an important boundary condition for modeling the movement of Antarctic ice sheet but difficult to measure systematically at a continental scale. Earlier GHF maps suffer from low resolution and possibly biased assumptions in tectonism crustal generation, resulting significant uncertainty. We present new map Antarctica constructed by empirically relating upper mantle structure known United States. map, compared with previously seismologically...
Abstract The Antarctic mantle and lithosphere are known to have large lateral contrasts in seismic velocity tectonic history. These suggest differences the response timescale of flow across continent, similar those documented between northeastern southwestern upper North America. Glacial isostatic adjustment geodynamical modelling rely on independent estimates variability effective viscosity. Recent improvements imaging techniques distribution stations now allow resolution both vertical...
Abstract We develop a 3‐D isotropic shear velocity model for the Alaska subduction zone using data from seafloor and land‐based seismographs to investigate along‐strike variations in structure. By applying ambient noise teleseismic Helmholtz tomography, we derive Rayleigh wave group phase dispersion maps, then invert them structure Bayesian Monte Carlo algorithm. For stations, perform joint inversion of receiver functions curves. The forearc crust is relatively thick (35–42 km) has reduced...