Focal mechanism analysis and parameter estimation of Zhangbei-Shangyi earthquake from differential SAR interferometry

On 10 January, 1998 an earthquake of M s=6.2 occurred in the Zhangbei-Shangyi region of North China. The surface seismic deformation was measured in the previous study using the 3 pass ERS-1/2 SAR differential interferometric technology (D-INSAR). In this note the focal mechanism of Zhangbei-Shangyi earthquake is estimated from the D-INSAR measurement of surface deformation based on a standard elastic dislocation model for seismic displacement The inversion procedure is an iterative, linear least-squares algorithm. Through the relation between the focal parameters and displacement in the line of sight direction measured in the radar interferogram, the optimum focal parameter set is derived. The results show that the seismic fault of Zhangbei-Shangyi earthquake is a thrust fault dipping SW with a Large right-lateral displacement component. The strike and dip are 95° and 30° respectively on a fault patch of 12 km long by 14 km wide. Its hypocenter is located at N40°58′, E114°21′, and 7.5 km in depth. The estimated slip vector is 0.728 m with a rake of 105.95°, the trend of slip is NW13.26°, and M 0 2.69×1018N · m.