电阻率层析成像在沉积区隐伏断层探测中的应用

The application of high density electrical method to concealed fault detection in sedimentary plain

电阻率层析成像是开展城市活动断层探测的方法之一。本文以天津蓟运河断裂探测为例,对电阻率层析成像在沉积区隐伏断裂探测中的应用进行了尝试。野外施工中采取了多项针对性措施,获得了较可靠的电阻率层析成像剖面;在详细分析测区钻孔资料的基础上进行剖面的地质解释,并与浅层人工地震结果进行了对比。探测结果显示,蓟运河断裂为一条第四系断裂并表现出一定的分段性,北段最浅上断点深达25 m,为一条晚更新世活动断层,南段为55 m左右,是一条中更新世中晚期断层。本次探测工作表明,利用电阻率层析成像在沉积区进行隐伏断层探测可以获得良好的效果。

Resistivity tomography is a part of the methods for conducting fault detection in urban areas.In this paper,the application of resistivity tomography to the detection of concealed faults in sedimentary areas was attempted with the fault detection of the Tianjin Canal as an example.The Wenner symmetrical quadrupole device(Wenner α)was employed to data acquisition.In order to obtain higher quality raw data,the authors adopted a number of targeted measures in the field construction.Data processing and inversion adopted a wide range of engineering circles.Using the RES2DINV software,the authors obtained a more reliable resistivity tomography profile.In the geological interpretation of the section,detailed analysis was carried out based on borehole data of the survey area in comparison with the results of shallow artificial earthquakes.The results show that the Jiyunhe fault is a Quaternary fault and shows a definite segmentation.The shallowest upper fault point in the northern section is about 25 m deep,which is a late Pleistocene active fault,and the southern section is about 55 m,which is a middle late Pleistocene fault.This probing work shows that the use of resistivity tomography for the detection of concealed faults in the sedimentary area can achieve good results,but in the process of geological interpretation,the sedimentary evolutionary environment,the geological structure of the basement,and the conductive ion density of the formation should be closely combined with each other.The impact is particularly dependent on other detection results to ensure the harmonization of relevant consequences.