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Since the mid-1990s, the local seismic network of the University of Cologne has produced digital seismograms. The data all underwent a daily routine processing. For this study, we re-processed data of almost a quarter century of seismicity in the Northern Rhine Area (NRA), including the Lower Rhine Embayment (LRE) and the Eifel Mountain region (EMR). This effort included refined discrimination between tectonic earthquakes, mine-induced events, and quarry blasts. While routine processing comprised the determination of local magnitude ML, in the course of this study, source spectra-based estimates for moment magnitude MW for 1332 earthquakes were calculated. The resulting relation between ML and MW agrees well with the theory of an ML ∝ 1.5 MW dependency at magnitudes below 3. By applying Gutenberg-Richter relation, the b-value for ML was less (0.82) than MW (1.03). Fault plane solutions for 66 earthquakes confirm the previously published N118° E direction of maximum horizontal stress in the NRA. Comparison of the seismicity with recently published Global Positioning System–based deformation data of the crust shows that the largest seismic activity during the observation period in the LRE occurred in the region with the highest dilatation rates. The stress directions agree well with the trend of major faults, and declining seismicity from south to north correlates with decreasing strain rates. In the EMR, earthquakes concentrate at the fringes of the area with corresponding the largest uplift.

During the construction of an underground museum in the historic city center of Cologne, Germany, large parts of the Roman and medieval city are being excavated. The newly excavated remains as well as remains of the Roman city, which had already been excavated in 1954, exhibit structural damages. While at first deficiencies in the construction were assumed to be the cause of the damages, in 2003 a seismogenic origin was suggested. To further test this hypothesis of seismically induced slope movements and other possible causes, a multidisciplinary project was started. One step in this project is the documentation of the damages using a 3D laser scanner, followed by a quantitative damage analysis. This article presents the 3D documentation and the quantitative damage analysis of a recently excavated medieval cesspit. The 8.3m-deep cesspit was mapped during 11 campaigns using a phase-based 3D laser scanner. Due to the static conditions of the cesspit, the structure could not be excavated in its entirety. After the excavation of every 1-2m-section, restoration work had to be done to avoid a collapse of the construction. The laser scanning technique offered the possibility of working parallel to the excavation so the original conditions of each section could be documented before the restoration. The resulting models were used to identify, classify, and quantify the structural damages of the cesspit.

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