3D joint inversion of magnetotelluric and magnetovariational data to image conductive anomalies in Southern Alberta, Canada

Abstract

It is well known that magnetotelluric (MT) impedance can be distorted by near-surface inhomogeneities (NSI), which complicates the interpretation of MT data and the correct imaging of deep geoelectrical structures. This paper demonstrates that the inclusion of magnetovariational (MV) tipper data in a three-dimensional (3D) inversion jointly with MT impedance provides better resolution of deep conductive anomalies than stand-alone MT impedance. This is significant because MV data can be collected alongside the MT impedance data for virtually no additional cost. Electric and magnetic fields in forward modeling are determined using the integral equation (IE) method. The inverse problem is solved with the reweighted regularized conjugate gradient (RRCG) method with limited sensitivity domain. We present the results of both a synthetic model and case study using EarthScope data gathered in Southern Alberta, Canada. In both cases, the joint inversion provides more accurate information about deep conductive anomalies than the inversion of impedance stand-alone data.