基于浅层地震勘探与钻孔联合地质剖面探测的苏北盆地倪湖庄-七里墩断裂研究

浅层地震勘探与钻孔联合地质剖面探测是隐伏断层定位与活动性鉴定的基本手段，需在实际工作中不断总结完善。通过采用浅层地震勘探技术，查明了淮安市区附近隐伏断裂的基本格局，并结合钻孔联合地质剖面探测与第四纪年代学测定，确定了新发现的倪湖庄-七里墩断裂的最新活动时代及活动特征。倪湖庄-七里墩断裂为近南北走向、倾向西的高角度正断层，断层倾角72°～82°，探测断裂长度为43 km。浅层地震勘探揭示其断面具有近直立或呈S形的上下反倾特点，指示具有走滑性质。该断裂错断了北东走向淮阴-响水断裂与北西走向无锡-宿迁断裂，最新活动时代为中更新世中晚期。本次探测工作对技术方法进行了探索，并提出以下建议:针对新发现的隐伏断裂，宜采用从已知点向外逐次探测的方式，即完成上一条测线的设计、施工与解译工作后，根据探测结果布设下一条测线；基于地震时间剖面进行钻探设计时，既要考虑断层两盘反射波组延伸与变形特征，又要考虑物探解译上断点与实际上断点的埋深差异；在河流下游开展钻孔联合地质剖面探测与地层对比时，需充分考虑局部地貌条件差异与第四纪海平面对陆域地表过程的影响。

Nihuzhuang-Qilidun Fault Detecting Based on Shallow Seismic Exploration and Drilling Joint Geological Profile in Subei Basin

It’s a fundamental method for buried fault location and fault activity identification to carry out shallow seismic exploration and drilling joint profile works. Furthermore, the method needs to be constantly summarized and improved in practical work. This paper made a thorough investigation of basic pattern of buried faults in Huaian City urban district by means of shallow seismic exploration, combined with drilling joint geological profile detection and Quaternary chronology test. The latest activity age and characteristics of the newly discovered fault, named Nihuzhuang-Qilidun fault, are defined by then. Nihuzhuang-Qilidun fault is a high-angle normal fault, 43 kilometers investigated, trending nearly South-North and dipping west with dip angle of 72o to 82o. Shallow seismic exploration reveals the up-and-down anti-dip characteristics of the fault plane that is nearly upright or S-shaped. This indicates the strike-slip characteristic of the fault. The fault crosses the NE-trending Huaiyin-Xiangshui fault and the NW-trending Wuxi-Suqian fault. Its latest activity era traces to middle and late Middle Pleistocene. Exploration on the technical method is also carried out in the practical detecting process and the following three suggestions are summarized. It is advisable to take the approach of successive detection from the known point outwards studying newly discovered buried fault. The further survey line should be laid out according to the detection results after completing the design, construction and interpretation of a former survey line. It is necessary to consider not only the extension and deformation characteristics of the reflected wave groups on the two sides of the fault, but also the difference in the burial depth between the breakpoint on the geophysical interpretation and the actual breakpoint while designing drilling plan based on seismic time profiles. The effects of local differences in geomorphological conditions and Quaternary sea level on land surface processes need to be considered when carrying out drilling joint geological profile detection and stratigraphic correlation in the lower reaches of the river.