The Study Of Two-dimensional Joint Inversion Of Gravity, Magnetic,electrical And Seismic Based On The Cross-gradient Constrains And Its Application

Geophysical methods can be divided into the gravity,magnetic,seismic and electrical method,etc.Each method can evaluate the petrophysical characteristics of underground medium from a single aspect,which can only reflect one profile of underground medium.In order to acquire underground information with greater accuracy,study on joint inversion has become a trend of recent research and development.The joint inversion can not only overcome the limitation of the single inversion,but also can reduce the multi-solution problem of inversion by inverting the underground medium simultaneously with the help of the rock physics relationship or the relationship between the spatial structure of rocks.This paper studied single inversions of four different physical methods including the magnetotelluric sounding,gravity,magnetic,seismic first arrival traveltime,and described the structural relationship between different physical properties with cross-gradient function.We implemented the cross gradient two-dimensional joint inversion including gravity,magnetic,electric and seismic by introducing the cross-gradient function into the objective function.Secondly,based on the cross-gradient joint inversion algorithm above,a single abnormal body and dual abnormal body theory model trial were carried out respectively.After the comparation and the analysis between joint inversion results and single inversion results,we found that the results of joint inversion are closer to the true model both on the property value and the space geometry,which verify the reliability and validity of cross-gradient joint inversion.Finally,we applied the cross-gradient joint inversionalgorithm to the field data collected in Changbai Mountain basalt covered area,which includes controlled source audio magnetotelluric sounding(CSAMT)data,gravity data and magnetic data.Compare to the single inversion,the result of joint inversion showed better structural similarity.We gave an elaborate geological explanation according to the inversion result combining the surface geological condition,and finally deduced the integrated interpretation section of measuring lines,which reflects the deep layer structure of the study area and provides powerful basis for the accurate judgment of deep geological body.