北京南口-孙河断裂带(北段)的结构及活动性

通过可控源音频大地电磁测深(CSAMT)、浅层地震和高密度电法地球物理探测手段建立的联合剖面对比,同时开展钻探工程及古地磁样品测试,对南口-孙河断裂带(北段)结构及活动性进行研究。南口-孙河断裂带(北段)由1条主断裂和1条次级断裂组成,断裂带宽约400m,表现为阶梯状断层,向上延伸至第四系。第四纪以来,断裂带活动显著,体现为松散层浅部引张的特点。根据断裂两盘第四纪以来各阶段累积垂直落差,计算出主断裂及次级断裂的活动速率。主断裂在早更新世、中更新世、晚更新世、全新世活动速率分别为0.161mm/a、0.072mm/a、0.468mm/a、0.52mm/a,次级断裂在早更新世、中更新世、晚更新世、全新世活动速率分别0.049mm/a、0.052mm/a、0.223mm/a、0.04mm/a。

A study of structure and activity of the north part of Nankou-Sunhe fault in Beijing

In this paper, three geophysical exploration methods, i.e., controlled source audio-frequency magnetotelluric sounding (CSAMT), shallow seismic and high density resistivity method, were used to establish combined profile for comparison together with drilling engineering and paleomagnetic sample tests, to study the structure and activity of the north part of Nankou-Sunhe fault. The north part of Nankou-Sunhe fault consists of one main fault and one secondary fault. The fault zone is as wide as 400m, exhibiting a step fault extending upwards to the Quaternary strata. Since Quaternary, the activity of fault zone has been remarkable, which reflects the extensional stress environment in the shallow loose layer. According to the accumulated vertical drop of the two plate of the fault in various stages of the Quaternary period, the activity rate of the main fault and its secondary faults were calculated. The main fault in the Early Pleistocene, Middle Pleistocene, Late Pleistocene and Holocene were 0.161mm/a, 0.072mm/a, 0.468mm/a and 0.52mm/a respectively. The secondary fault in the Early Pleistocene, Middle Pleistocene, Late Pleistocene and Holocene were 0.049mm/a, 0.052mm/a, 0.223mm/a and 0.04mm/a respectively.