The Uppermost Mantle Structure in China from Pseudowave Tomography

We have obtained pseudowave velocity images of the uppermost mantle beneath China by performing tomographic inversion of travel time differences between Sn and Pn. The arrival pairs were selected from the Annual Bulletin of Chinese Earthquakes from 1984 to 2005. The dataset includes 50,136 arrival pairs from 11,470 earthquakes recorded by 116 stations. The average pseudowave velocities are 10.6 km/s. The preliminary tomographic results show that 1) the pseudowave velocity is high in the Tarim and Junggar basins, the Ordos craton, the southern region of the Sichuan basin, and the Taiwan Strait; and 2) the pseudowave velocity is low in North China, the North-South Seismic Zone, and the central and western Tibetan Plateau. The pseudowave velocity pattern obtained is very similar to the distribution of Pn and Sn velocities in the study area.