Regional characteristics of stress field in the southern part of the north-south seismic belt in China and its relation with plate movement

Abstract

The regional characteristics of stress field in the southern part of the north-south seismic belt (NSB) have been analyzed in detail based on the mechanism solutions of 134 medium and large earthquakes from 1933 to 1991. The results show that the southern part of the NSB is a shallow earthquake zone where most earthquakes are caused by the strike-slip faulting. There is a systematic distribution of the directions ofP- andT-axes in the western and the eastern regions of the southern part of the NSB.P- andT-axes in the western region are in the NE-SW direction and in the NW-SE direction.P- andT-axes in the eastern region are oriented in NW-SE and NE-SW, respectively. The directions ofP-axes in the western and the eastern regions show a pattern of a reversal “V” as a whole. The boundary between the eastern and western regions coincides with that between the Tibetan Plateau and the Yangtze crustal block. Based on a lot of mechanism solutions, the result indicates that the direction ofP-axes roughly shows the consistent distributions from the Himalayan collision zone to the eastern region and from the eastern coast collision zone in Taiwan to the eastern region of southern part of the NSB, respectively. It is suggested that the tectonic force due to relative movement between the Indo-Australian and the Eurasian plates is transmitted from the Himalayan collision zone to the western region of the southern part of NSB, simultaneously, the tectonic force due to the relative movement between the Philippine Sea and the Eurasian plates is transmitted from the eastern region coast in Taiwan to the eastern region of the southern part of NSB, and control the stress field there, respectively.