Cenozoic fault development in the central segment of the Upper Rhine Graben: Constraints from 3D-seismic data north of Karlsruhe (SW-Germany)

The Cenozoic graben filling is currently investigated for heat storage potentials (DeepStor-project). The structural model based on 3D-seismic and borehole data constrains the geometry and sedimentary thicknesses of potential reservoirs of the DeepStor area north of Karlsruhe. Beside these site specific addressed questions the structural model was used to improve understanding of the development of structures and sedimentary units during Upper Rhine Graben development. The c. 44 km2 3D-seismic area is dominated by two major (N)NE-(S)SW-striking, W-dipping Leopoldshafen and Stutensee growth faults showing normal displacements of several hundred meters, most likely displacing crystalline basement rocks. Fault shadowing effects reduce imaging quality, identification and resolution of seismic reflectors with increasing depth mainly in the footwall. Footwall strata of the Leopoldshafen dip at very shallow angles to the E. Major growth strata along the Leopoldshafen fault comprise the early Miocene Hydrobia beds implying major fault activity during early Miocene times. Fault growth strata display migration of fault activity towards rift interior with time. NNW-striking en echelon normal faults, linked with relay ramps and antithetic faults, are limited to Cenozoic strata unconformably overlaying middle Jurassic rocks. Fault length – displacement analysis of individual faults indicate complex concomitant major and minor faulting activity, tip migration and subsequent fault linkage of minor fault segments that have evolved during progressive transtension.