Three-dimensional velocity images beneath the Chinese continent

Abstract

In this paper three-dimensional velocity images beneath the Chinese continent and adjacent regions are reconstructed, using P-wave travel-time residuals of regional and distant earthquakes in seismic tomography method, supplied by Chinese seismic networks and ISC (International Seismic Center). The velocity images show lateral heterogeneity of the crust and upper mantle beneath the Chinese continent and adjacent regions, which persists down to at least 1100 km deep. The correlation between the velocity images and the known surface geological features can be traced down to a depth of 110 km. Below 220 km this correlation is not obvious. The images at 45⁻⁰ km (immediately above the Moho) and 45⁺⁰ km (below the Moho) show clearly that the crust of the Chinese continent can be divided into two parts approximately along the 102.5°E longitude. The eastern part of the crust is thinner than the western part. The velocity images at 400 km and 600 km also display differences between the eastern and western parts. This means that the tectonic differences between eastern and western China may exist in the whole upper mantle.