西宁盆地北西缘南门峡—台子地区断裂构造地球物理探测

摘要

The temporal-spatial distribution characteristics of fault structures on the northwestern margin of Xining basin were investiga-ted by using the audio-magnetotelluric method and 2D seismic exploration,with the purpose of providing the hydrogeological borehole properly so as to carry out the comprehensive investigation and evaluation of hydrogeology,environmental geology and engineering geolo-gy in eastern cities of Qinghai Province,find out the stratigraphic structures and geological structures,and study geophysical characteris-tic parameters in the key region.The results show clearly that there exists Xiamen thrusting-nappe fault on the northwestern margin of Xining basin,which dips NW,with dip angle about 65°.The other two fractures were found in the river valley,away from mountains,and both are presumably associated with Nanmenxia strike-slip fault.In addition,the response characteristics of stratigraphic lithology,appar-ent resistivity and the velocity of seismic reflection wave were summarized.The hydrogeological borehole was drilled to verify the exist-ence of Xiamen thrusting-nappe fault.The drilling coring is quite consistent with the results from the geophysical exploration methods. Several fault fracture zones exist in this borehole penetrating the Neo-Proterozoic crystalline limestone.%为开展青海省东部城市重点地区水文地质、环境地质和工程地质综合调查评价,查明重点地区地层结构和地质构造,进行地球物理特征参数研究,采用EH-4音频大地电磁法和二维地震勘探两种技术方法探测西宁盆地北西缘南门峡—台子地区断裂构造空间展布特征.探测结果查明了南门峡—台子地区发育倾向NW,倾角约65°的硖门逆冲推覆断裂;河谷内远离山前发育规模较小的两条裂隙,推断与南门峡走滑断裂相关.与此同时,总结了南门峡—台子地区地层岩性、视电阻率和地震反射波波速之间的响应特征.硖门逆冲推覆断裂经钻孔取芯验证,与物探勘查成果吻合,钻孔内发育多处断层破碎带,穿透新元古界花石山群克素尔组结晶灰岩.