长垣断陷的地壳浅部结构和构造——地震反射剖面结果

摘要

为研究长垣断陷的地壳浅部结构和断裂浅部构造特征,跨长垣断陷完成了一条长度49 km的中深层地震反射剖面和一条长度7 km的浅层地震反射剖面.根据获得的地震反射剖面,结合区域地质资料,分析研究区的地壳浅部结构和断裂活动特征.结果表明,长垣断陷是一个东深、西浅的箕状断陷;黄河断裂为西倾的铲形正断层,其浅部错断了埋深约190 m的第四纪地层,其下部错断了多组反射地层和盆地基底,属第四纪以来的隐伏活动断裂;长垣断裂浅部错断了新近纪地层的底界,向下延伸至基底之下,属前第四纪断裂.本文研究成果为新乡市及其邻区的活动构造研究和地震危险性评价提供了地震学证据.%In order to investigate crustal shallow structures and fault shallow tectonic features crossing the Changyuan fault depression,we completed a 49 km multiple shallow seismic reflection profile and a 7 km shallow seismic reflection profile.According to the seismic reflection profiles and combined with the regional geological data,we analyze the crustal shallow structures and the fault shallow tectonic features in the study area.The results show that Changyuan fault depression is a deep east and shallow west dustpan-like subsidence,and the Cenozoic basement of the fault depression plunges from west to east;Huanghe fault is the west dipping spade shaped normal fault,and this fault disrupts 190 m Quaternary strata in the shallow part,disrupting multi-group Cenozoic lays and the crystalline basement.Therefore,it is a buried active fault in the Quaternary period;Changyuan fault disrupts the bottom of Neogene strata in shallow part,and it extends below the crystalline basement,therefore it is a Pre-Quaternary fault.The result provides seismological evidence for active tectonic research and seismic risk evaluation in Xinxiang and its neighboring districts.