Estimation of ground motion distribution during the 1920 Haiyuan earthquake using Ground motion model considering site effects and the uncertainty of magnitude

The 1920 Haiyuan earthquake occurred on 16 Dec. 1920, almost one hundred year ago. The epicenter of the earthquake is located in Haiyuan County, Ningxia Hui Autonomous Region, China. The magnitude of the earthquake is estimated to be M_s8.5, but M_w is estimated between 7.6-8.3, with a large uncertainty. Since lack of detailed investigation on damage of the earthquake, the seismic intensity distribution estimated for the earthquake are also variated.

In this study, based on the information of the active faults caused the earthquake, the distribution of V_S30 estimated in the area, we employ an ground motion models proposed by Si and Midorikawa (1999) to estimate the distribution of seismic intensity caused by the earthquake. Since moment magnitude of the earthquake is estimated with a large uncertainty, we use Mw between 7.6 to about 8.3 for the calculation, and check which one makes the best fit for the estimated and investigated seismic intensity.