重力剖面和激电测深联合勘测在涡河断裂研究中的应用
Application of Joint Exploration of Gravity Profile and IP Sounding Method to the Study of Guohe River Fault

为查明涡河断裂的位置、性质等参数,选择重力剖面和激电测深联合勘测方法,对指定区域进行物探勘测工作。结果表明:由密度差异引起的重力异常位置和岩石电阻率、极化率异常位置基本吻合,说明以重力剖面和激电测深为手段的联合勘测是查找断裂的有效方法。
The Guohe River fault originates from Bozhou,Anhui Province,passing through Guoyang to Mengcheng.According to regional geological inspection,this fault has an exclusive anomaly in gravity and magnetic aspect.In the light of being a hidden fault and thick upper crust,there are few investigations about it,and they tend to be more concerned about gravity and magnetic observations,remote sensing,and historical documents.Therefore,deep geophysical inspection is increasingly important to figure out its characteristics.In order to determine the horizontal location and feature of the Guohe River fault,both the gravity profile and IP sounding method are implemented in the research area's geophysical prospecting.The gravity profile is mainly based on the gravity anomaly,generally caused by density differences,which often indicates the existence of faults. It is easily operated,highly efficient,and low cost.In this paper,57 gravity points have been observed to detect the potential gravity anomaly in a relatively bigger area to narrow down the inspected region for the IP sounding method.During research,the gravity profile had a length of 4 500 m,in a northeast direction,crossing over Guohe River to the north,about 13 km away from Mengcheng county.Results show that gravity profile value has a very obvious decline between the 54th and 55th observing points with an amplitude of 1.0 × 105 m·s2,which could be possibly due to the surface elevation difference of 3 m.In any case,the values of the gravity profile increase from southwest to northeast,in the same direction of the Guohe River fault.Aside from the non-background gravity anomaly,there possibly exists a geological anomaly 500 m underground which has density differences that result in the gravity anomaly,located between the 49th and 53rd observing points,which could be the result of Guohe River fault.on the basis of this conclusion,the IP sounding method,which is based on the resistivity and polarizability change of the rock underground,is applied in this gravity-anomaly area.During the research,the symmetry quadrupole vertical sounding method is utilized,beginning at the 42nd gravity observing point and continuing for 1 600 m and 14 acquisition points.When it comes to data processing,the apparent resisitivity and apparent polarizability are considered to be the main parameters for this method.As for the apparent resistivity profile,there lies a tiny contour lift,about 300~500 m deep.This