多种物探方法在湘潭城区活断层勘探中的应用

杨梅洲—木鱼湖断裂位于湘潭城区,要查明其位置和性质,地球物理勘探干扰因素多,施工条件不好。调查中分别采用天然电场选频法、高密度电阻率法和地质雷达等方法进行勘探,并通过开挖等方式进行验证,3种物探方法各有特点:天然电场选频法仪器轻便、勘探线布置灵活,干扰因素较少,工作效率高,特别是利用其动态信息确定断层平面位置准确;高密度电阻率法勘探结果比较直观,特别是对断层性质的确定形象,但勘探布极的工作量较大,受地形等因素影响较大,在城区很多地方无法正常开展工作;地质雷达勘探成果形象直观,但设备成本高,勘探受地形等因素影响大,勘探深度有限,一般对表层效果较好。

EXPLORATION OF FAULT ZONE IN URBAN XIANGTAN WITH SELF-POTENTIAL FREQUENCY,HIGH DENSITY RESISTIVITY AND GEOLOGICAL RADAR METHODS

The Yangmeizhou-muyuhu Fault is situated just the inner urban area of Xiangtan City.There are many disturbance factors in process of geophysical prospecting.The site condition is not good to the use of a single geophysical method.Three methods of geophysical exploration were used to investigate and to identify the position and nature of the fault.They are the self-potential frequency method,the high density resistivity method,and the geological radar.Besides,the interpreted results from the geophysical methods are verified with logging of actual excavations It is found that the three methods have different characteristics as follows.The self-potential frequency method has the features: light equipment,exploration line layout flexibility and less interference factor.Especially it is precise to use the time-dependent data to determine fault plane location.The high density resistivity method has the features: it is easy visual observation and comparison of the fault zone;the exploration workload is extremely large;the topography has a large effect;testing in urabn area is difficult.The geological radar method has the features: image visual exploration results;high cost of equipment;topography has large effect;limited depth exploration;and the better results only for surface prospecting.