Seismic results as a-priori knowledge for airborne TEM data inversion — A case study

We present a case study where a-priori knowledge from high resolution reflection seismic data is used to improve airborne time-domain electromagnetic data inversion. The a-priori knowledge constrains layer boundaries and lateral resistivity change during the inversion process.The object for the case study is the North Sea island Föhr that was affected by several glaciations and inherits a complex Quaternary and Tertiary geology. The freshwater lens and the local geology were investigated by several geophysical surveys. A SkyTEM survey with following laterally constrained inversion provides the resistivity distribution of the island and several 2-D high resolution seismic reflection surveys give structural information. Vertical seismic profiles provide reliable velocity information for time-to-depth-conversion. Seismic horizons and a combined interpretation yield to a-priori constraints for the SkyTEM inversion.We demonstrate how a-priori constraints enhance the inversion to a reliable direction. From the 3-D data cube of 1-D inversion models we extract an example and reinterpret the geophysical results. With the new inversion it is possible to image a till layer with subjacent sand in a larger range than before.

► Airborne TEM inversion is combined with a-priori information from seismic data.
► Spatial resistivity distribution becomes more reliable
► Relevant geological features are exposed much better.