Combined interpretation of SkyTEM and high-resolution seismic data

Airborne electromagnetic methods (AEM) are used extensively in groundwater investigations, often in combination with high-resolution seismic data. Despite the frequent use of this mapping strategy, only a few cases are found in the literature. In this study, comparisons and interpretations were made based on AEM (SkyTEM) and high-resolution seismic data from an area covering 10km ² in the western part of Denmark. As support for the interpretations, an exploration well was drilled to provide lithological and logging information in the form of resistivity and vertical seismic profiling. Based on the resistivity log, synthetic SkyTEM responses were calculated with a varying number of gate-times in order to illustrate the effect of the noise-level. At the exploration well geophysical data were compared to the lithological log; in general there is good agreement. The same tendency was recognised when SkyTEM results from the area were superposed onto seismic sections. Comprehensive geological knowledge is necessary in order to introduce layer boundaries from one method interactively in the data handling of the other. However, in cases where resistivity transitions are positively correlated to reflections, SkyTEM data supports the interpretation of weak reflections, and can also support the correlation of reflections both internally and between seismic lines. Besides contributing lithological information, the AEM survey provides gross three-dimensional structural information, whereas seismic data contributes with more detailed structural information in two dimensions.