Seismic anisotropy in the upper mantle beneath continental interiors is generally complicated, with contributions from both the lithosphere and the asthenosphere. Previous studies of SKS splitting beneath the eastern United States have yielded evidence for complex and laterally variable anisotropy, but until the recent arrival of the USArray Transportable Array (TA) the station coverage has bee...

[1] We use Rayleigh and Love wave Green’s functions estimated from ambient seismic noise to study crustal structure and radial anisotropy in the tectonically complex and seismically active region west of the Sichuan Basin and around the Eastern Himalaya Syntaxis. In agreement with previous studies, low velocity zones are ubiquitous in the mid‐lower crust, with substantial variations both latera...

The D′′ region in the lowermost mantle beneath the Caribbean and Central America is investigated using shear waves from South American earthquakes recorded by seismic stations in North America. We present a large-scale, composite study of volumetric shear velocity heterogeneity, anisotropy, and the possible presence of a D′′ discontinuity in the region. Our data set includes: 328 S(Sdiff )-SKS ...

[1] Finite temperature ab initio molecular dynamics calculations were performed to determine the high temperature elastic and seismic properties of the perovskite and post-perovskite phases of pure endmember Al2O3. The post-perovskite phase exhibits very large degrees of shear-wave splitting. The incorporation of a few mole percent of Al2O3 into MgSiO3 is predicted to have little effect on the ...

3-D migrations of time-lapse seismic monitor data acquired during steam injection show dramatic and complex changes in the reservoir zone over a wide area, compared to baseline seismic data recorded prior to steam injection. Anticipated large decreases in seismic P-wave velocity Vp near the injection well correlate with the presence of a hot desaturated steam zone. Unanticipated large increases...

We present ab initio calculations of the high-temperature axial c/a ratio of hexagonalclose-packed (hcp) iron at Earth’s core pressures, in order to help interpret the observed seismic anisotropy of the inner core. The calculations are based on density functional theory, which is known to predict the properties of high-pressure iron with good accuracy. The temperature dependence of c/a is deter...