[1] Shear waves that traverse the lowermost mantle exhibit polarization anomalies and waveform complexities that indicate the presence of complex velocity structure above the core-mantle boundary. Synthetic seismograms for horizontally and vertically polarized shear waves (SH and SV, respectively) are computed using the reflectivity method for structures with low-velocity sheets (‘‘lamellae’’),...

[1] Broadband shear wave signals from 15 deep South American earthquakes reveal small-scale variations of the D00 shear velocity discontinuity beneath the Cocos Plate. Deconvolution by average event source wavelets allows multiple event and California station combinations to be double-array stacked in 4 geographically separate reflection point bins with lateral dimensions of about 200 km. Refle...

0031-9201/$ see front matter 2011 Elsevier B.V. A doi:10.1016/j.pepi.2011.10.001 ⇑ Corresponding author. Tel.: +81 92 642 2515; fax E-mail addresses: [email protected] [email protected] (S.-i. Karato). Viscosity of the D00 layer of the Earth’s mantle, the lowermost layer in the Earth’s mantle, controls a number of geodynamic processes, but a robust estimate of its viscosity has been hamp...

Received 30 January 2004; revised 14 May 2004; accepted 14 June 2004; published 13 August 2004. [1] Shear velocity properties of D00 beneath the central Atlantic Ocean are explored using predominantly European seismic recordings of intermediate and deep focus (>100 km) South American earthquakes. Broadband data are analyzed and, when possible, corrected for upper mantle models of receiver-side ...

[1] We have determined by first principles the athermal elastic constant tensor, single crystal and aggregated acoustic velocities, and anisotropy of the recently discovered post-perovskite MgSiO3 polymorph. This phase may be the most abundant mineral in the D00 region. We find that the post-perovskite phase has similar bulk modulus and larger shear modulus than perovskite at relevant pressures...

[1] The shear velocity structure in the lowermost 500 km of the mantle beneath the Caribbean and surrounding areas is determined by seismic tomography applied to a suite of Sd-SKS, ScS-S, (Scd + Sbc)-S, and ScS-(Scd + Sbc) differential times, where (Scd + Sbc) is a pair of overlapping triplication arrivals produced by shear wave interaction with an abrupt velocity increase at the top of the D00...

Received 10 December 2004; revised 27 July 2005; accepted 5 October 2005; published 9 March 2006. [1] Velocity heterogeneity and seismic anisotropy in the D00 region beneath the southern Pacific Ocean is investigated using broadband shear waves from southwest Pacific and South American earthquakes recorded by permanent and temporary stations in Antarctica, Australia, South America, and on islan...