Study On Two Dimensional Joint Inversion Of Direct Current Resistivity And Audio Magnetotelluric

Due to the limitations of multiple solutions and detection depth range of single geophysical exploration methods,Comprehensive geophysical method is generally selected for complex geological exploration,which is based on independent inversion of single method data for comprehensive interpretation.The Direct current resistivity sounding method(DCR)is a geometric sounding method to explore in the shallow layer with high resolution.The audio magnetotelluric method(AMT)is a frequen cy sounding method,which is applied to medium and deep exploration with relatively low resolution,and it is susceptible to local anomalies on shallow surfaces.Based on this,this paper takes a two-dimensional joint inversion research of Direct current resistivity sounding method and audio magnetotelluric method,and carries out the data synchronous processing and inversion of the two methods,then discusses the feasibility and practicability of the algorithm.It provides theoretical basis and reference f or DCR and AMT comprehensive exploration.This study applied Finitude difference method to realize forward modeling of DCR and AMT.Different data was taken from the same grid subdivision and discretization,LU algorithm was used to solve linear equations,and the sensitivity matrix was solved by fusion method.The OCCAM joint inversion research was then carried out based on that data space.We verified the feasibility of the proposed algorithm through the simple high and low resistance model response data of joint inversion,and then built three complex degree different geoelectric models,and analyzed the applicability by discussing different theoretical datas from joint inversion results.Furthermore,The influence of noise level,initial model,selection frequency,measuring point spacing and device type on joint inversion were also analyzed.The results of research show that: DCR and AMT combined inversion can take into account both shallow and deep geological information,which to some extent makes up for the shortcomings of these two methods in separate inversion,and helps to improve the resolution of shallow geological bodies in middle and deep electrical exploration.In DCR and AMT joint inversion,an appropriate initial model should be selected based on the resistivity changes of surrounding rock and target body.3.DCR device type has a small impact on joint inversion,but the density of measuring points directly restricts the horizontal resolution of inversion results,while the sparsity of frequen cy limits the vertical resolution of inversion results.