3-D characteristics inversion of hypocenter fault-plane of the 1668 Tancheng great earthquake

The Tancheng M 8.1/2 great earthquake in 1668 was the largest seismic event recorded in history in eastern of China,which occurred in Shandong section of Tanlu fault zone,meanwhile,the small earthquakes at the hypocentral region are still frequent now.This study inversed and calculated the source fault's fracture form of the1668 Tancheng 81/2 earthquake based on the basic parameters of more than 100 small and medium re-positioning earthquakes occurred in nowadays around the hypocentral region.We get the results as follows:the strike of source fault is 21.6°,the dip angle is 89.5°,the slip angle is 148.9°,the fault length is about 180 km,the lower-boundary depth is about 32 km and the buried depth of upper boundary is about 4 km.All the parameters show that the focal fault is a NNE-trending upright right-lateral strike-slip fault And the surface projection of source fault is basically coincident with Anqiu-Juxian fault which is located at eastern-graben of Yishu fault belt(F5).The inversion is analyzed according to the results of the surface seismic fault and intensity distribution of 81/2 earthquake,and the basic parameters are discussed combining earthquake-depth distribution and seismic-wave velocity profile in the focal area and so on.They showed that all kinds of results could be verified by each other,and the inversion has reached the ideal results.This study indicated that,for the great earthquake region with abundant present-day seismic data,it is feasible to invert its fault characteristics.