【摘要】 采用浅层高分辨率多次覆盖共中心点地震反射技术,对2003年10月25日民乐—山丹地震隐伏发震构造:民乐—永昌断裂和童子坝河断裂,进行了地球物理勘探研究.地震勘探剖面揭示,民乐—永昌隐伏断裂与先前推测的断裂性质基本一致,为逆冲断层,倾向北东,倾角越往深部越缓,约在30°—45°之间,测线处上断点深度小于15m;童子坝河隐伏断裂根据地震剖面结合地貌特征及区域应力分析,可判定具正断层特性,倾向南西,倾角约77°,并非以前所认为的逆冲断层.上述两条断裂于晚第四纪表现出了一定的新活动性,其共同作用导致了2003年10月25日民乐—山丹MS6.1和MS5.8地震的发生.更多还原

【Abstract】 Shallow high-resolution P-wave CMP reflection method was used to investigate Minle-Yongchang fault and Tongzibahe fault,which are considered to be the causative faults for the October 2003 Minle-Shandan earthquakes. The reflection seismic images show that the faulting style of Minle-Yongchang fault is basically the same as the style inferred from structural geology investigation and hydro-geological information. This fault section has the characteristics of reverse fault and dips toward NE with a dip angle of about 30°—45°,being a little steep in shallow part and gentle at depth. Upper bounds of the fault lie at less than 15 m depth along the survey line. Meanwhile,based on a combined analysis on seismic profile data,geomorphic features and regional stress information,we conclude that the Tongzibahe fault is not a reverse fault but a set of normal faults,dipping toward SW with a dip angle of about 77°. These two faults have showed a certain amount of seismic activity in late Quaternary era,and the 2003 MS6.1 and MS5.8 Minle-Shandan earthquakes are the result of joint action of the two faults.更多还原