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Abstract:
The Lower Rhine Embayment in western Germany is one of the most important areas of earthquake recurrence north of the Alps, facing a moderate level of seismic hazard in the European context but a significant level of risk. This study deals with the impact of a scenario earthquake with a moment magnitude of 6.5 occurring along the Erft fault system south-west to the city of Cologne, the fourth largest German city with more than one million inhabitants and accommodating important industrial facilities. Since the city is located on thick layers of Quarternary sediments, the geological discontinuities at depth will have a significant influence on the duration and the amplification of ground-motion. Based on a new, harmonized and spatially highly resolved, model of the sedimentary cover, the sensitivity of spectral intensity measures to the site response analysis method is assessed employing random vibration theory approaches. Corresponding damage calculations are conducted in terms of European Macroseismic Scale (EMS-98) damage grades. Residential buildings and buildings with mixed residential and commercial occupancy are included in the corresponding calculations only, in line with most seismic risk assessment studies which have traditionally focused on residential typologies. Results from the damage calculations are presented in terms of number of buildings exposed to bands of EMS-98 intensity levels and probabilities of EMS-98 damage grades for residential buildings and buildings with mixed residential and commercial occupancy. Casualties in the city and the neighboring districts are estimated by means of the PAGER empirical method using population counts at the quartier (“Stadtviertel”) level in Cologne, the “Bezirk” level in Bonn and Aachen and at the municipality (“Gemeinde”) level for the surrounding areas, all of these comprised within the district (“Regierungsbezirk”) of Cologne.
