A Proeliminary Study On Magnetotelluric Anisotropy In The Northern Margin Of West Qin-ling Mountain-eastern Margin Of North Qilian Mountain

By applying the anisotropic analysis of the magnetotelluric sounding (MT), this paper aims to gain a preliminary knowledge of the geo-electric structure at the northern margin of west Qin-ling Mountain—eastern margin of north Qilian Mountain.In this paper, firstly, the basic equations of the isotropic and anisotropic medium are analyzed. Then, the process and method for the MT field data acquisition is depicted detailedly, with focus on the magnetotelluric response and discrepancy of the isotropic and anisotropic medium models. In this way, some initiative means are obtained to identify the MT anisotropy. Furthermore, a piece of computer software for directly calculating MT response functions from the self-power spectrum data (EDI) is independently developed. By analyzing the MT field data, the impact of the strike angle on the apparent resistivity, impedance phase and others MT response functions is studied. Finally, by using the one-dimensional anisotropic inversion for all the observed data, basing on inversion results, the geo-electric structure of the study area is initially analyzed. Meanwhile, a preliminary structural interpretation for the inversion result is processed.The research results in this area show: the shallow geo-electrical structures are well corresponding to the regional geological of the study area, and the inferred fault zone is also in line with the actual situation. Through the MT anisotropy, the deep geo-electrical structure of the study area is preliminarily obtained.