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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Radial anisotropy in the northeastern Tibetan Plateau
from Surface Wave Tomography
Three-dimensional anisotropic shear wave velocity structure and radial anisotropic model of lower crust and upper mantle beneath
NE Tibetan plateau are constructed from measurements of Love wave dispersions and previously obtained Rayleigh wave dispersion
in order to answer two important questions regarding the plateau dynamics: (1) whether the deformation in the crust and upper mantle is coupled; (2) whether asthenosphere upwelling exists beneath the NE Tibetan Plateau. We have analyzed Love waves recorded
at the Northeast Tibet Seismic (NETS) array and applied the two-plane-wave tomography method to compute average and 2-D phase
velocities. Transverse component seismograms from 66 events at 36 stations were filtered at 14 center frequencies with a narrow
bandwidth of 10 mHz. Average
phase
velocity varies from 3.55 km/s at 20 s to 4.55 km/s at 100 s, which are higher than previously
obtained Rayleigh wave
phase
velocities at corresponding periods. 2-D variation of Love
phase
velocity was calculated at the periods
from 20 s to 100 s using 2-D, Born sensitivity kernels. Low-velocity anomalies are imaged along and to the south of the Kunlun fault
at each period, similar as from Rayleigh wave tomography. However, the magnitude and size of the low
phase
velocity are much
stronger and larger in Love wave images than in the Rayleigh wave maps. We invert the 2-D
phase
velocities of Rayleigh and Love
waves in the period range from 20 to 100 s simultaneously, to construct a radially anisotropic shear wave velocity model. Such
anisotropic properties, which cannot readily be obtained from body wave studies only, can provide new insights into geodynamic
process in this tectonically actively region.