Feasibility Study of Multi-dimensional HEM Forward Modelling - Example of Cuxhaven Buried Valley

Abstract

Helicopter-borne electromagnetic data sets are extensive in size and multi-dimensional modelling and inversion of the entire data set is in many cases impractical. On the other hand, the commonly used 1-D approaches might result in models with artefacts or distortion when higher dimensional structures are present. A complex procedure is required to enhance the resistivity models for such areas. One has to identify those areas either to investigate if artefacts are the potential cause of ambiguous structures in 1D-based sections/pseudo-3D models or to model and invert those using higher dimensional approaches. Multi-dimensional modelling and inversion codes vary considerably regarding their advantages but also their restrictions. The latter mainly result from structure related requirements but also from memory usage and computation time. Thorough testing of various codes is required to find the most applicable one for the specific data set. Small scale higher dimensional models obtained represent the local structure but might have shortcomings on the regional trend. Hence, merging those models with the overall model of the entire data set is a challenge. The focus of this paper is the feasibility study of multi-dimensional forward modelling programs based on the example of the Cuxhaven buried valley.