Joint Seismic and Magnetotelluric Exploration around the Geothermal Research Well Gross Schönebeck (NE German Basin)

Geophysical exploration for geothermal resources is often challenging because information on the parameters of interest such as porosity, permeability, fluid content, etc., cannot be observed directly. Conventional (seismic) structure images are usually not sufficient to locate potential geothermal targets. Magnetotelluric (MT) and seismic methods provide information about the resistivity and velocity distributions of the subsurface in similar scales and resolution. The lack of a fundamental law linking the two parameters, however, limits a joint interpretation to a more qualitative analysis. Using a statistical approach in which resisitivity and velocity models are investigated in the joint parameter space, we can identify regions of high correlation between the two model parameters. Back-mapping of these regions onto the spatial domain allows us to identify common classes which can then be compared with lithological information. Application of this technique to a seismic - MT profile in the area of the Groß Schönebeck geothermal site, allows us to identify a number of classes in accordance with local geology. In particular, a high velocity - low resistivity class is interpreted as related to salt lows, where highly fractured anhydrite might produce enhanced permeability.