Efficient 3D inversion of MT data using integral equations method and the receiver footprint approach: application to the large‐scale inversion of the EarthScope MT data

Abstract

In this paper we present an accurate and efficient method of 3D inversion of MT data. We address two common problems of 3D MT inversion: computational time and memory requirements. The method is based on an IE formulation of the EM forward modeling problem. We apply the quasi-Born approximation to compute the Frechet derivative. This allows us to use only one rigorous forward modeling per inversion iteration. We have also developed a receiver footprint approach which dramatically reduces the computer memory needed for the Frechet derivative calculations. We apply our 3D inversion method to the MT data collected in the western United States as a part of the EarthScope project. The inverted electrical conductivity distribution agrees reasonably well with geological features of the region as well as with 3D MT inversion results obtained by other researchers.