Seismic hazard assessment for the Lower Rhine Embayment before and after the 1992 Roermond earthquake

Abstract

A regional probabilistic seismic hazard analysis for the Lower Rhine Embayment was published by the authors in 1975 and updated in 1984 as part of a comprehensive study for the former Federal Republic of Germany and adjacent regions. The seismic zones of the lower Rhine Embayment were found to belong to the most active in western and central Europe. This contribution presents the modifications required after the occurrence of the Roermond earthquake of April 13,1992. New frequency-magnitude curves λ(> M) are derived as the essential quantitative input, applying the generalized Gumbel distribution for magnitude extremes. Completion of the former data for the years l980-1992 leads to distinct changes of λ(> M) in the seismic zone in which the epicenter of the Roermond earthquake is situated. Revised frequency-intensity curves λ(> I) are computed with the Monte-Carlo simulation techniques using code PSSAEL developed earlier by the authors. Only small changes are found. For example, an intensity (MSK) I = VII is now expected at Roermond for future events with a probability of 4.9.10-4/year instead of 2.4.10-4/year. The regional seismic risk is illustrated by two recomputed hazard maps of the Lower Rhine Embayment.