Seismological Studies On The Characteristics Of Jiashi Source Region From 1997 To 2003

During the year of 1997, 1998 and 2003, three groups of strong earthquakes (total of 10 with magnitude equal or greater than Ms6.0) occurred in a small area between Jiashi and Bachu counties in Xinjiang autonomous region, western China (Hereinafter is called the Jiashi source region), separately. In order to get a more systematic knowledge about the characteristics of the source region for the whole time period, seismological studies are conducted on the seismic fault structures, the rupture process of strong earthquakes, the temporal-spatial migrating process of earthquakes, as well as the state of stress field. By applying double difference tomography method to the arrival time data recorded by two temporal seismic arrays, a high resolution velocity structure was imaged, providing us information of the medium environment in and around the source area. By relocating earthquakes occurred in the period from 1997 to 2003 systematically for the first time, combined with the focal mechanisms of the main shock, seismic fault structures and their rupture manners are revealed. Through performing the moment tensor inversion using 3-component broadband seismic waves at regional distances, the focal mechanisms for 54 moderate-sized earthquakes are determined, which offsets the gap of no moment tensor solutions for moderate-sized earthquakes in Jiashi source region previously. And furthermore, the state of stress field is investigated using stress tensor inversion method. Through the source rupture process inversion of three Ms6 earthquakes, some important conclusions have been obtained about the features of rupture process of events with different focal mechanisms, about the relationship between the main shock rupture and the aftershock location, as well as about the relationship between the main shock slip and the aftershock's focal mechanisms. The main results of this thesis are summarized as follows:According to the results of double difference tomography, low P velocity and low Vp/Vs are detected in the source region of 1997 strong earthquake swarm, suggesting the existence of fluids within high aspects fractures in and around the source region.1024 events from Apr. to Oct.1998 were precisely relocated by using 3-D velocity...