Abstract: A trial geochemical prospecting for active faults in urban area through the survey of soil gases has been conducted in Fuzhou City, China. This paper demonstrates the principal methodology and results of the trial prospecting. As compared with field investigation of active fault, the detection of buried active faults in urban area is more complicated since there are additional unfavorable environment and conditions such as road, constructions, refilled soils, rubbish dumps and soil/water pollution etc. The trial is aimed at the assessment of the effectiveness of soil gases survey for buried fault prospecting in urban area, and the identification of the surface locations of two buried faults in Fuzhou City. The trial includes the following comparative surveys: 1)different types of sites(soils); 2)different radon detectors and 3)different detecting items(adsorbed mercury, free mercury and radon in soil). Totally, 18 traverses of free mercury gas surveying have been conducted, along with 8 traverses of free radon gas and 1 traverse of adsorbed mercury surveying. The anomalies of different items are basically accordant, but it seems that radon gas is more sensitive to the influence of environmental factors such as groundwater level. The locations of two buried faults determined by soil gases are in good accordance with those determined by seismo-geologic investigation. The results of soils gases survey have also been compared with those of shallow seismic exploration. The comparison shows that the anomalies detected by the two different prospecting techniques are fairly coincident(the "fitting ratio" is about 70%); the false soil gas anomalies seem to occur in such a site as bridge side, abandoned construction bases and rubbish dumps.

Key words: radon, mercury, soil, buried fault, Fuzhou City

摘要： 在城市环境中进行隐伏断层地球化学探测试验是一次新的尝试.试验探测内容包括:不同地球化学测项(土壤气汞和土汞、土壤气氡等)、不同类型测氡仪器(FD-125,FD-3017RaA)、不同探测场地(稻田、菜地、林区、道路、回填土和市区街道绿化带等).地球化学与浅层地震勘探结果的比较表明,2类异常点的对应率约为70%,表明地球化学方法在福州市环境下的隐伏断层探测中是一种有效的方法;地球化学"伪异常"出现的可能部位是小桥边、废弃建筑物地基、路边垃圾堆放地等.

关键词: 地球化学探测, 土壤气, 隐伏断层, 福州市