关键词: 双差地震成像, 重新定位, 速度结构, 海城余震区, 盖州震群

Abstract: In this study, the earthquake observation reports recorded by 34 regional seismic stations during the period from August 1975 to Dec 2017. Source the method of double difference tomography inversion. We got the Velocity structure and the Earthquake location of the Southbern Liaoning area by TomoDD. Nodes methed is used in model parameterization of seismic tomography and ART-PB is used in forward calculation. Damped least square method is used in inversion. Many people care about the Evaluation of solutions ,the result of checkerboard test is given in this study. We calculated all seismic relocations in Liaonan area and got the positioning results, better distribution of P wave velocity on several layers 4km,13km,24km,33km.We got the results of the P wave velocity structure.At same time we got the location of almost the earthquake has been recorded. We found the location of earthquake mainly concentrated in two areas: Haicheng aftershock area and Gaizhou earthquake swarm activity area. The distribution of seismicity in this area is obvious in NW direction The results of P-wave tomography show that the shallow velocity structure is consistent with the geological structure in southern Liaoning .Haichenghe fault in Haicheng aftershock area has high velocity body in the shallow layer and low velocity body in the depth of 4-12km, and the intrusion of low velocity body is deepening eastward The result of P wave velocity structure and wave velocity ratio elaborated the affect of Reservoir seepage to Wen Chuan M8.0 earthquake .We find the affect of Reservoir seepage in the southwest of zipingpu Reservoir closest to the epicenter in Wenchuan is not more than 8km in depth. We found neither obvious low velocity anomaly in Wenchuan main shock depth,nor obvious high value anomaly of Vp/Vs ratio.Which means penetration of water haven’t reached the depth of Wenchuan main shock,and showed that the water was not the direct factor caused Wenchuan Earthquake.There is a high velocity body at the end of different segments of Jinzhou fault, and the Gaizhou earthquake swarm at the end of the fault occurs in the high velocity body area. It is speculated that the activity of the Gaizhou earthquake swarm may be caused by the rise of water saturation of rocks due to the intrusion of liquid under the condition of stress accumulation.

Key words: Double difference seismic imaging, seismic relocation, velocity structure, Haicheng aftershock area, Gaizhou earthquake swarm