Inversion of electromagnetic geosoundings using coordinate descent optimization

A coordinate-descent inversion algorithm is tested for a non-separable regularization operator. The algorithm is based on a homotopy moving regularization operator from l(2) to l(1). Results are presented for both linear and nonlinear problems. The linear case corresponds to electromagnetic soundings typically used for prospecting down to a few tens of meters. The first nonlinear case corresponds to direct-current resistivity soundings, which are typically useful for prospecting down to hundreds of meters. The last application is to magnetotelluric soundings that can reach penetration depths of tens of kilometers. Developed models are comparable with the original for the synthetic cases and with those obtained by other researchers for field data.