Background Seismicity and its Application to Seismic Hazard Assessment in the North China Region

Historic earthquake activity in the north China region has been intense.However,no moderate earthquake has occurred in the last more than ten years in the region since the 1998 MS6.2 Zhangbei earthquake.The quietness of moderate to strong earthquake is quite prominent in the region.In this paper,we use the small earthquake record between 1970 and 2009 to study the background seismic activity in the north China region.We presented the spatial distributions of seismic parameters including b-value,maximum magnitude and annual probability of occurrence of an earthquake equal to or larger than M6.0.Our results show that the regions with low b-value include the Yunchen region in the Shanxi rift,the Shuqian region located in the Tanlu Fault Zone and the Shijiazhuang region in the Taihangshan block.The analysis by synthesis shows that seismicity in the north China region is mainly affected by the regional dynamic factors in depth.