Study On Geophysical Mapping Method In Loess Covered Area

According to the needs of special geological and geomorphic area mapping pilot project of China geological survey,this paper carried out comprehensive geophysical exploration method for loess covered area geological mapping experimental research.In this paper,the basic principles of three exploration methods,namely,shallow seismic reflection wave method,audio-frequency controlled source magnetotelluric sounding method and high-precision gravity exploration method,as well as actual field measurement methods and structural interpretation principles,are introduced at first,and then the physical parameters based on the exploration process are analyzed.Papers in the research of shaanxi baoji mapping test area,on the basis of the geological and tectonic situation,has carried on the experimental zone of high precision gravity,CSAMT and shallow reflection seismic data processing,mainly in the gravity profile inversion,electromagnetic sounding inversion and seismic imaging method to comprehensive interpretation and effect analysis,obtained the coverage area of concealed fault location and scale,the depth of bedrock surface and rolling and the information such as sedimentary layers,finally build 2451 km~2 fill in drawing area of 3D geological model.The comprehensive geophysical mapping analysis in the test area shows that the high-precision gravity exploration can be used to determine the undulating state of the bedrock surface and the deep large faults,and the inversion interpretation can be carried out with the comprehensive constraints of the seismic results,which can reduce the multi-solution of the inversion results.The shallow seismic reflection wave method has a high vertical resolution and can accurately detect the fluctuation of underground bedrock surface,the stratification of geological structure and the thickness information of loose layer covering loess.The audio-frequency magnetotelluric sounding with controllable source can reach a larger exploration depth and make up for the shortcoming of shallow reflection seismic reflection wave method in deep exploration.In loess covering area geological mapping,according to the advantages of the above three kinds of geophysical exploration methods and application limitation,between various exploration methods complement each other,combined with the corresponding method of the situation of geological achievements of section and fill in the drawing area,detect complete drawing area sedimentary cover lower geological information,find out the bedrock surface of ups and downs,concealed fault,concealed,sediment stratified rock mass,rock property,such as geological problems,to provide coverage in geological mapping work with technical support.