We provide a synthesis of the long-term earthquake activity in the region of northwest Europe between the Lower Rhine Embayment and the southern North Sea. Reevaluated historical earthquake and present-day seismological data indicate that much of the known seismic activity is concentrated in the Roer graben. Nevertheless, the three strongest known earthquakes with estimated magnitude ≥ 6.0 occurred outside of this active structure, in the northern Ardenne, the southern North Sea, and the Strait of Dover. During the past 700 yr, destructive earthquakes generally have occurred at different locations, indicating a migration of seismicity with time. Because in plate interiors the present seismic activity does not necessarily reflect past and future activity, we discuss the necessity to use the geologic record to infer long-term earthquake activity. Thus, we synthesize and discuss paleoseismic investigations in the Roer graben that provide evidence that large earthquakes with magnitude up to 7.0 have occurred since the late Pleistocene. We also show that tectonic deformation is close to or below the accuracy of current geodetic techniques. Thus, it is necessary to have longer periods of observation to compare present geodetic deformation rates with the observed seismic moment release and the geologic strain rates. Based on these results, we present methods to define seismic zoning and evaluate the maximum credible earthquake and its magnitude relevant for seismic hazard assessment.

The northern Rhine area covers an area of more than 40,000 km 2 and is one of the most important areas of earthquake recurrence in Europe north of the Alps. The Lower Rhine Embayment, a part of the northern Rhine area that extends over parts of western Germany, eastern Belgium, and the southern Netherlands, displays basin-like subsidence and, along with the Roer valley graben, has been the source of most of the historical and recent earthquake activity, particularly along the western border faults. Other important earthquake-prone areas include the Stavelot-Venn Massif and the Neuwied Basin, the latter of which is an area of periodically intensive micro-seismicity. Seismic instrumentation in the area has accumulated steadily since the early 1950s and presently consists of ∼50 stations. Although the strongest instrumentally recorded earthquake in the region occurred in 1992 near Roermond, with a local magnitude of 6.0, studies of historical earthquakes, such as Vervier (1692) and Düren (1756), estimate macroseismic magnitudes of 6.8 and 6.4, respectively. Paleoseismic studies indicate that even stronger, surface-rupturing earthquakes have occurred during the Holocene. The recent M L 4.9 earthquake in Alsdorf in 2002 caused some structural damage and was preceded by several small earthquakes and was followed by several aftershocks. Seismic hazard evaluation is hampered by the sparse earthquake record. A hybridized instrumental and historical earthquake catalog compiled from events over the past 300 yr combined with seismotectonic aspects indicates a maximum magnitude of 7.0. A site-intensity map based on macroseismic intensities from the hybridized catalog identifies concentrations of recent activities in the western part of the Lower Rhine Embayment, east of the city of Aachen.