Iterative modelling of AEM data based on a priori information from seismic and borehole data

Airborne electromagnetic methods (AEM) have become an important part of groundwater mapping in a wide range of geological settings. However, as for all geophysical methods, the results of the inversions are non-unique and it is therefore relevant to include a priori information in order to obtain the most realistic geological inversion outcome. Despite the extensive use of AEM, only a few studies describe the effect of including a priori information in large-scale AEM surveys. In this study, ancillary information from seismic and borehole data are used as a priori information. The basis for the study is a densely spaced airborne transient electromagnetic dataset (SkyTEM) from a 100 km2 area in the western part of Denmark. Six different inversions are performed, and these are formulated as blocky and smooth inversions with different amounts of a priori information in the deepest part of the sections. The use of a priori information has a significant influence on the interpretation of the sections in the lowermost part of the sequence. Furthermore, the middle part of the sections, which are not constrained by the a priori information, show a significant change through the different inversions. Thus, the study shows that the inclusion of a priori information to the deeper part, significantly enhances the understanding of the geology both in the intermediate and deep levels.