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Upper Mantle Shear and Compressional Velocity Structure of the Central US Craton: Shear Wave Low‐Velocity Zone and Anisotropy
Author(s) -
Rodgers Arthur,
Bhattacharyya Joydeep
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2000gl012112
Subject(s) - geology , shear wave splitting , shear velocity , anisotropy , shear (geology) , mantle (geology) , geophysics , velocity gradient , longitudinal wave , s wave , low velocity zone , seismology , shear waves , wave propagation , physics , mechanics , petrology , lithosphere , tectonics , optics , turbulence
One‐dimensional upper mantle velocity structure is estimated by modeling P, SV and SH body‐waveforms sampling the central United States. The resulting model features a thick mantle lid with a positive velocity gradient. A significant shear wave low‐velocity zone (6% velocity reduction) is required below the lid however the compressional velocities are not reduced. The paths studied lie along the fast axes of teleseismic shear wave splitting measurements and absolute plate motion. We observe splitting of upper mantle refracted shear‐waves, with the transverse component slow relative to the radial component. In order to fit the shear wave arrivals and satisfy teleseismic shear‐wave splitting observations we infer azimuthal anisotropy (maximum 1.6%) distributed throughout the mantle lid and low‐velocity zone, with increasing anisotropy with depth.