A comparison of 2D inversion of RMT and 1D weighted joint inversion of ground-based and helicopter-borne electromagnetic data

Abstract

A Pleistocene buried valley, the Cuxhaven Valley, located in Northern Germany, is extensively studied by three different electromagnetic methods. In order to enhance the resolution of the very shallow subsurface structures, the radiomagnetotelluric (RMT) measurements were conducted on the buried valley in addition to the helicopter-borne electromagnetic (HEM) and transient electromagnetic (TEM) data, which were available from the study area along the same profile. First, the RMT soundings are interpreted using the conventional 1D and 2D inversion algorithms. The RMT interpreted models inferred two-layer structure of the subsurface up to a depth of 30 m, which comprises a resistive layer at the top. Available lithological data is used for correlating the resistivity values derived from the 2D inversion of the RMT data with the subsurface formation. Subsequently, a 1D weighted joint inversion algorithm is utilized to interpret these three data sets jointly. The 2D interpreted models of RMT soundings are compared with the 1D weighted joint interpreted models of RMT, HEM, and TEM soundings.