Shear velocity structure of crust and uppermost mantle in China from surface wave tomography using ambient noise and earthquake data

摘要

We present a 3D model of shear velocity of crust and upper mantle in China and surrounding regions from surface wave tomography.We combine dispersion measurements from ambient noise correlation and traditional earthquake data.The stations include the China National Seismic Network,global networks,and all the available PASSCAL stations in the region over the years.The combined data sets provide excellent data coverage of the region for surface wave measurements from 8 to 120 s,which are used to invert for 3D shear wave velocity structure of the crust and upper mantle down to about150 km.We also derive new models of the study region for crustal thickness and averaged S velocities for upper,mid,and lower crust and the uppermost mantle.The models provide a fundamental data set for understanding continental dynamics and evolution.The tomography results reveal significant features of crust and upper mantle structure,including major basins,Moho depth variation,mantle velocity contrast between eastern and western North China Craton,widespread low-velocity zone in midcrust in much of the Tibetan Plateau,and clear velocity contrasts of the mantle lithosphere between north and southern Tibet with significant E–W variations.The low velocity structure in the upper mantle under north and eastern TP correlates with surface geological boundaries.A patch of high velocity anomaly is found under the eastern part of the TP,which may indicate intact mantle lithosphere.Mantle lithosphere shows striking systematic change from the western to eastern North China Craton.The Tanlu Fault appears to be a major lithosphere boundary.