Two‐dimensional magnetotelluric inversion using reflection seismic data as constraints and application in the COSC project

We present a novel 2‐D magnetotelluric (MT) inversion scheme, in which the local weights of the regularizing smoothness constraints are based on the envelope attribute of a reflection seismic image. The weights resemble those of a previously published seismic modification of the minimum gradient support method. We measure the directional gradients of the seismic envelope to modify the horizontal and vertical smoothness constraints separately. Successful application of the inversion to MT field data of the Collisional Orogeny in the Scandinavian Caledonides (COSC) project using the envelope attribute of the COSC reflection seismic profile helped to reduce the uncertainty of the interpretation of the main décollement by demonstrating that the associated alum shales may be much thinner than suggested by a previous inversion model. Thus, the new model supports the proposed location of a future borehole COSC‐2 which is hoped to penetrate the main décollement and the underlying Precambrian basement. We introduce a new regularization for 2D inversion of MT data that transfers structural boundaries from reflection seismic images The new method is effective in resolving abrupt changes in resistivity and evaluating the compatibility of MT and seismic data Our findings for MT and seismic from the Caledonian orogen support the proposed location for future drilling through the main decollement