关键词: 大陆强震, 碰撞带, 影响区, 地震活动特征

Abstract: China's continent lies at the southeastern corner of the Eurasian Plate. It is squeezed by N-NNE-trending compressional force of the Indian Plate in the southwest, influenced by the NW- NNW -trending subduction zone of the Pacific and Philippine Plates in the east, and confined by the Siberian- Russian block of Eurasian Plate in the northwest. According to the data obtained from 22 GPS stations in 1994 and in 1996, it is suggested that the horizontal relative motion of China's continent is mainly compressional in north-south direction, and weakly tensile in east-west direction. Taking the North-south seismic belt as a boundary, the crustal movement is stronger in the west and weaker in the east, while the motion along block boundaries is dominated by sinistral compressional shearing. This situation may indicate that the crustal motion of China's continent is dominated by the northeastward squeezing of Indian plate. In addition, it is suggested that the most prominent and most important tectonic motion in China's continent should be the India-Eurasia collision, which causes crustal deformation in a vast regions including the rise of the Qinghai-Xizang Plateau and the formation of a series of seismic belts. Considering the west China and its surrounding regions as a uniform seismic zone, we discuss in this paper the control and influence of the joint action of the surrounding plates on continental strong earthquakes of China. In addition, the characteristics of seismic activities in West China and its surrounding regions are discussed as well. We find that the temporal distribution of strong earthquakes in this seismic zone is characterized by rhythmicity. According to the spatial migration of strong earthquakes, this region can be geologically divided into two seismic zones: the collision zone and the influenced zone, bounded by the suture zone between Lasa and Qiangtang blocks. We find that the earthquake activities in these two zones are interactively increased and decreased. The discovery of this feature will be useful in the assessment of the intensity of seismic activity in the broad North China.

Key words: Continental strong earthquake, Collision zone, Influenced zone, Seismic activity