A structural model from local earthquake tomography: Application to present-day tectonics of the Upper Rhine Graben

We present a novel numerical approach to construct quantitative tectonic models from crustal velocity distributions derived from local earthquake tomography. Independent constraints on the location and orientation of structures are obtained from earthquake hypocenters and seismic reflection profiles. An application of this method is given for the southern end of the Upper Rhine Graben (northwestern Europe). Kinematic boundary conditions are imposed on the structural model to investigate the large scale intraplate deformation in the region. A 3-D finite element code is used to calculate the displacements, the distribution of stresses, and the potential for brittle failure in the Graben. The modeling takes into account the intersection and curvature of crustal faults. The results demonstrate the dependence of fault interaction in the system on kinematic conditions, as well as the influence of minor faults on the kinematics of major basin bounding master faults. We show that although most of the deformation in the region is taken up by the eastern boundary faults of the Rhine Graben, all faults in the system have the potential to be (re)activated. In particular, a fault system underlying the front of the Jura fold and thrust belt appears to accommodate a large part of the intraplate deformation.