The Roer Valley Graben earthquake of 13 April 1992 and its seismotectonic setting

A moderately sized pure, normal dip-slip earthquake occurred in the Roer Valley Graben (RVG) near Roermond, The Netherlands on 13 April 1992 at 1h 20m UTC. This contribution presents an overview of the locations, fault-plane solutions and magnitudes obtained for the mainshock and the aftershocks by the different scientific groups involved in their analysis. The observed maximum intensity of VII is compared with that of other earthquakes in the region to illustrate the relatively low level of damage caused by the mainshock.
Using SH and Lg waves recorded at seven local and regional broadband stations, we determine a seismic moment of 1.4 × 10¹⁷ Nm, a static stress drop of 9.7 MPa and an average displacement of 33 cm over a rupture surface of approximately 11 km².
The seismotectonics of the region extending from the RVG to the city of Liège including the western part of the Rhenish Massif (WRM) and the eastern part of the Brabant Massif (EBM) is analysed based on the Roermond earthquake studies and data collected since 1985 by the Belgian seismic network. The geographical distribution of focal mechanism reveals four different seismotectonic regimes in this area. From stress tensor inversion we find that ₃ coincides with the minimum horizontal stress component in the RVG, the WRM and possibly in the EBM, while in the Liège region ₃ is approximately vertical. The minimum horizontal stress component shows a 30° rotation to the north in the WRM and the Liège region and possibly 50° in the EBM when compared with the minimum horizontal stress component in the RVG.