【摘要】 通过跨银川断陷盆地,完成了一条长68.9 km的高分辨深地震反射探测剖面,首次获得了银川盆地地壳精细结构、地堑型断陷盆地深部断裂系(黄河断裂、银川断裂、贺兰山东麓断裂)特征及深浅构造关系.结果表明:银川断陷盆地上地壳为双程走时8 s(深度约20km)反射面以上的区域,上地壳上部地层层位丰富,地层分段连续性较好,上地壳下部地层分层特征不明显,地质构造简单;下地壳(8～13 s)反射能量较弱,反射同相轴不明显;下地壳下部壳幔过渡带(13 s附近)由一组能量较强、持续时间较长(1.5 s)的反射波组组成,厚度约4.5 km.芦花台断裂、银川断裂分别于12～12.5 km、18～19 km深处交汇于贺兰山东麓断裂,贺兰山东麓断裂于28～29 km深处交汇于黄河断裂,黄河断裂为错断Moho面的深大断裂,银川地堑为以黄河断裂为主,其他断裂为辅组合而成的负花状构造.根据贺兰山东麓断裂和银川断裂的相互关系,认为贺兰山东麓断裂对1739年平罗银川8级地震起主要控制作用.更多还原

【Abstract】 A high resolution deep seismic reflection profile of 68.9 km long across the Yinchuan faulted basin has been accomplished which for the first time yields the fine crustal structures, characteristics of deep fault system (Yellow River fault, Yinchuan fault and eastern piedmont fault of Helanshan) of faulted basin of graben style, and the relationship between shallow and deep structures in Yinchuan basin. The results show that the upper crust is the region above a reflector with 8 s two-way traveling time (about 20 km deep), there are many strata in the upper part of upper crust where the continuity of different segment of stratum is good, and there is no obvious layered feature in the lower part of upper crust, where the geological structure is simple. The reflection energy is weak in the lower crust (8～13 s), where reflection events are not obvious. The crust-mantle transitional zone (around 13 s) below the lower crust consists of a group of reflection sequences that have stronger energy and longer duration (1. 5 s), and the thickness is about 4.5 km. Luhuatai fault and Yinchuan fault merge into the eastern piedmont fault of Helanshan in the depth of 12～12. 5 km and 18～19 km, respectively, the eastern piedmont fault of Helanshan merges into Yellow River fault in the depth of 28～29 km, and Yellow River fault is a deep fault cutting the Moho. Yinchuan graben is a negative flower structure that is assembled mainly by Yellow River fault and secondarily by other faults. Based on the relationship between the eastern piedmont fault of Helanshan and Yinchuan fault, it is thought that the eastern piedmont fault of Helanshan plays a controlling role in 1739 M=8 Pingluo-Yinchuan earthquake.更多还原