P-WAVE VELOCITY STRUCTURE OF THE UPPER MANTLE ON THE MAINLAND AND THE MARGINAL SEAS OF CHINA

In this pater, the authors have studied the velocity structures of the upper mantle beneath South China and the marginal seas of China by using the first arrivals and some secondary arrivals of p-wave and have contrasted them with that in other regions: North China, Qinghai-Tibet plateau (Qing Zang Gaoyuan) and the North-South Seismic Zone. We have found that there are significant differences in velocity structure in the upper mantle not only beneath the stable platforms and tectonic-active zones, but also in different quasi-platforms. The lateral heterogeenity in velocity may continue to a depth of about 700 km. The authors try to explain this lateral heterogenity from the point of view of tetonic evolution in this paper.