Strong, sharp, negative seismic discontinuities, velocity decreases with depth, are observed beneath the Pacific seafloor at ∼60 km depth. It has been suggested that these are caused by an increase in radial anisotropy with depth, which occurs in global surface wave models. Here we test this hypothesis in two ways. We evaluate whether an increase in surface wave radial anisotropy with depth is ...

[1] The Hoggar swell in Algeria is one of the significant massifs of northwest Africa. The paucity of high‐ resolution geophysical studies of the crust and mantle beneath the massifs is mostly responsible for the heated debates about the depth of the source region of the Cenozoic volcanism and the closely related uncertainty about the mechanism that formed and maintains the high elevation of th...

Tomograms of the upper mantle, which represent perturbations in P-wave, shear wave speed, and bulk-sound speed, image the Indo-Australian plate subducting beneath the Eurasian plate along the Sumatra–Andaman arc. The detailed images of the subducting slab are well constrained by the large number of intermediate depth earthquakes and moderate seismic station coverage along the entire Indonesian–...

[1] The seismic structure of the crust and upper mantle of the southwestern United States is examined using receiver functions calculated from teleseismic arrivals recorded in the Colorado Plateau–Rio Grande Rift–Great Plains Seismic Transect (LA RISTRA) experiment. We apply receiver function estimation and filtering methods developed by Wilson and Aster (2005) to produce receiver functions wit...

iran is located in a roughly triangular deforming region, consisting of relatively undeformed shield areas to the southwest (arabia) and northeast and the more recently deformed, though currently inactive, southwest afghanistan block in the east. the current geological and tectonic setting of iran is due to the ongoing convergence between the arabian and eurasian plates, which resulted in the f...

H-κ stacking is a routinemethod for determining crustal thickness (H) and Vp/Vs (κ) using P-to-S (Ps) receiver functions. In this paper we show that S-to-P (Sp) receiver functions may also be used to determine crustal parameters. Sp provides independent information, complementary to Ps. We develop a method called H-V (crustal thickness-velocity) stacking where Ps and Sp receiver functions are s...

S U M M A R Y This study applies high-resolution Radon transform to a large set of SS precursors and explores the mantle reflectivity structure beneath 17 potentially ‘deep-rooted’ hotspots. The combined reduced time (τ ) and ray parameter (p) information effectively constrains the depth, spatial distribution and sharpness of upper-/mid-mantle reflectors. The olivine to wadsleyite phase boundar...

Receiver functions derived from body waves recorded in Iceland and on the Hawaiian Islands reveal a seismic velocity discontinuity at about 1050 km depth beneath the two regions of presumed mantle upwelling. The waveforms of the converted phases from the mid-mantle discontinuity indicate a velocity increase with depth. The lack of consistent scattering found in recent systematic searches for se...