Northern Europe would typically be classified as a relatively stable continental region where seismic hazard is low. Indeed, in comparison to active zones in the Mediterranean, seismic activity is low in northern Europe and the Lower Rhine graben region. Until recently, no one would have suspected that the normal faults related to graben structures in the Lower Rhine embayment could produce large earthquakes. Yet, on April 13, 1992, an Ms = 5.3 earthquake struck the city of Roermond in the Netherlands. This moderate earthquake is considered to be one of the major historical seismic events in this region, and it is stimulating concern among seismologists and geologists. Fundamental questions are being asked about fault behavior in the region and the earthquake distribution in time and space.