关键词: 苍梧M_S5.4地震, 重力场, 形变场, 地震危险性

Abstract: Based on the mobile gravity observation data in 2014-2016 in Guangxi and its adjacent areas, this paper systematically analyzed the changes of regional gravity field and its relation to the M_S5.4 Cangwu, Guangxi earthquake on July 31, 2016, and combined with GPS observation data and seismic geological survey results, discussed the temporal and spatial distribution characteristics of the changes of regional gravity field and its mechanism. The results show that:(1) Before and after the M_S5.4 Cangwu earthquake, the gravity anomaly changes near the earthquake area were closely related to the major faults in space, which reflects the crustal deformation and tectonic activities that caused the surface gravity change along the seismogenic fault in the period of 2014-2016; (2) The gravity changes near the epicenter before and after the M_S5.4 Cangwu earthquake showed an evolution process in which the positive gravity anomaly zone changed to the negative gravity anomaly zone, a gravity gradient belt appeared along NNE direction and the earthquake occurred in its reverse change process; (3) The epicenter of the M_S5.4 Cangwu earthquake located both near the gravity gradient belt and in the zero transition zone of the surface strain gradient and the edge of the high maximum shear strain rate area, the observational fact further proved that the dynamic image of gravitational field and deformation field have important instruction significance to the location prediction of strong earthquakes; (4) in recent years, the gravity dynamic change in northwestern Guangxi presented a four-quadrant distribution pattern, and there is the risk of generating earthquake of magnitude about 5 in the center of the quadrants.

Key words: M_S5.4 earthquake in Cangwu, gravity field, deformation field, seismic risk