Uppermost mantle structure beneath eastern China and its surroundings from Pn and Sn tomography

摘要

The Pn and Sn residuals from regional events provide strong constraints on the structure and lithological characteristics of the uppermost mantle beneath eastern China and its surroundings. With the dense Chinese Digital Seismic Network in eastern China, separate Pn and Sn tomographic inversions have been exploited to obtain P and S velocities at a resolution of 2 degrees x 2 degrees or better. The patterns of P velocities are quite consistent with the S velocities at depth of 50 and 60 km, but the amplitude of P wave speed anomalies are a little larger than those of S wave speed. The low P wave speed, high S wave speed, and low V-p/V-s ratio beneath the northern part of Ordos Basin are related to upwelling hot material. Abrupt changes in material properties are indicated from the rapid variations in the V-p/V-s ratio.