Horizontal magnetovariational responses in geothermal exploration: synthetic model studies

Abstract

Horizontal magnetic inter-station transfer functions, which are less distorted by near surface inhomogeneities and more sensitive to the deep targets, have been incorporated with other magnetotelluric data sets to delineate the electrical conductivity distribution in geothermal zones. Geothermal settings composed of salty fluid saturated faults and fractures, and hydrothermal alterations show a wide variation of the bulk resistivity. This makes electromagnetic methods, particularly magnetotellurics which is able to detect the geoelectric structures of deep targets, ideal techniques for the exploration of geothermal regions. In this research, the horizontal magnetovariational data are combined with other magnetotelluric transfer functions and their capabilities for improving the electrical conductivity structure obtained from 2D inversion process are examined. To this end, several synthetic models-representative of the conductivity changes in geothermal fields or conceptual modelshave been utilized. The results from two-dimensional (2D) inversion confirm the effectiveness of horizontal magnetic tensor as a part of the transfer functions, especially for the detection of deep conductive features.