Abstract: To test the effectiveness of DC and TEM soundings for urban active faults, experiments were carried out in Fuzhou City, Fujian Province in 2001. This paper is focusing on the test results of the Bayishuiku-Shanggan Fault, which is the major fault crossing the downtown of Fuzhou City. Two DC(DC-Ⅰ-1 and DC-Ⅰ-23)and three TEM(TEM-Ⅰ-1, TEM-Ⅰ-2 and TEM-Ⅰ-3)traverses were deployed in Bayishuiku area. DC experiment used a RESECS equipment. An array of 96 electrodes(192m long)was employed for the measurement, while a 16 electrode string(32m long)is prepared for rolling ahead at the end of the array for a long traverse. Electrode spacing is 2m. TEM used EM-47 and EM-67 systems. For EM-47 the measurements were made at the center of the transmitter loop with a dimension of 40m×40m. A large fixed loop with side length of 100～200m was employed for EM-67. Two adjacent loops overlap half of the side length. Site spacing is 10m for both EM-47 and EM-67. DC models show the electric structures at a depth range of 1 to 30m, while TEM models indicate those of 10 to 300m depths. DC model coincides excellently with the TEM model in the same traverse. All the DC and TEM models represent a layered structure with a strong vertical low resistivity anomaly in the middle part of each profile, which is inferred to be the main strand of the Bayishuiku-Shanggan Fault in the area. The fault appears to be several ten meters wide dipping NNE into the basement. The experiments suggest that the results will be much improved by using the combined DC and TEM method.

Key words: multi-electrode direct current method, transient electromagnetic method, Bayishuiku-Shanggan Fault

摘要： 为了检验高密度电法和瞬变电磁法在城市活断层探测中的有效性,在福州市区及周围进行了试验探测^①,文中主要介绍对八一水库尚干断裂的探测结果.八一水库尚干断裂是一条穿过福州市区的主要断裂带,其主断裂在八一水库测区位于一条由新店通往古城的水泥马路东侧,在横向上表现为东西宽几十米的电阻率低异常带,在纵向上从盖层底部向下延伸到基底深处.试验表明,高密度电法和瞬变电磁法可以互相补充和验证,从而提高整体探测效果.

关键词: 高密度电法, 瞬变电磁法, 活断层, 八一水库-尚干断裂