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Title:: Strong Earthquake Risk in Wuzhong-Lingwu Region of Ningxia Based on b-value

Author(s):: ZENG Xianwei; LI Wenjun; MA Chongzhi; CAI Xinhua; (Ningxia Hui Autonomous Region Earthquake Agency,Yinchuan 750001,Ningxia,China)

Keywords:: Wuzhong-Lingwu region; b-value; the maximum likelihood method; seismic risk; sparse segment of small earthquakes

摘要:: 利用1970年1月至2018年10月吴忠—灵武地区的地震精定位目录,基于b值平面分布以及沿活动断裂的震源深度剖面和b值剖面图等,分析了研究区发生强震的潜在危险性。结果表明:①新华桥附近存在发生地震的潜在危险性,强度为M_S5.1～5.4,但b值时序曲线表明该区域短期内发生中强地震的紧迫性不强; ②吴忠/郭家桥—高闸地区很可能是1921年2月22日吴忠南M_S6.0地震的发震位置,该地震震源深度应在15 km左右,上地壳浅部很可能未破裂; ③吴忠/郭家桥—高闸地区地壳浅部依旧存在发生强震的危险,孕震强度为M_S6.2～6.3,孕震深度在10 km以内。

Abstract:: In the paper,we relocated the earthquakes in Wuzhong-Lingwu region from Jan.,1970 to Oct.,2018 based on Hypo2000 and HypoDD methods.Then,analyzing the horizontal distribution of b-value,focal depth profile and b-value profile along active fault,we studied the potential risk of strong earthquakes in the study region.The results show that:① There is a risk of M_S5.1～5.4 earthquakes near Xinhuqiao area.However,the b-value time series curve does not support the occurrence of medium-strong earthquakes in the region in a short time.② The Wuzhong M_S6.0 earthquake on Feb.22,1921 is likely to occur in Wuzhong-Gaozha region.The focal depth of the earthquake is about 15 km,and the shallow part of the upper crust is probably unbroken.③ There is still a risk of strong earthquakes with M_S6.2～6.3 in the shallow crust of the Wuzhong-Gaozha region and the focal depth is within 10 km.