Lithospheric structure of the Chinese mainland determined from joint inversion of regional and teleseismic Rayleigh-wave group velocities

摘要

We processed a large number of vertical-component seismograms recorded by broadband seismic stations in and around China and ultimately retrieved –33 140 regional and –10 360 teleseismic fundamental-mode group-velocity measurements at 40 s periods, with fewer measurements for shorter and longer periods. We directly inverted the processed group-velocity measurements for a three-dimensional lithospheric S-velocity model of the Chinese mainland. Synthetic test results and data fit or misfit analysis demonstrated the reliability of our surface-wave tomographic inversion. The imaged upper-crustal low velocities are consistent with variations in sediment thickness; for example, the Tarim Basin, which contains a great thickness of sediments, is characterized by a strong, shallow, low-velocity anomaly. High lithospheric velocities are observed to varying depths in the North China Craton, Yangtze Craton, and Tarim Craton, indicating varying thicknesses of the lithosphere beneath these cratonic areas. Low asthenospheric velocities are widely imaged in eastern and southern China, around the Tarim Basin, and along a roughly north-south belt in central China. The low asthenospheric velocities in eastern and southern China are attributed to partial melting of a subducted slab associated with the westward subduction of an oceanic plate, while those in central China and around the Tarim Basin are attributed to Indian-Eurasian collision.