000005443 001__ 5443
000005443 005__ 20210928195715.0
000005443 037__ $$aCTALK-2021-0076
000005443 100__ $$aVan Noten, Koen
000005443 245__ $$aRecent seismic swarm activity in the Lower Rhine Graben (Germany, The Netherlands)
000005443 260__ $$c2021
000005443 269__ $$c2021-09-22
000005443 520__ $$aIn 2021, three tectonic seismic swarms occurred in Lower Rhine Graben (LRG; Germany, The Netherlands). The Rott low-magnitude seismic swarm (North Eifel, DE) started on 1 January 2021 close to the German-Belgian border near the western rim of the LRG. The two largest events occurred in January 2021 with local magnitudes of ML = 2.6 which were felt up to Aachen (~25 km radius). Similar to other low-magnitude tectonic seismic swarms in stable continental regions, the sequence lasted for months and more than 100 seismic events were measured. During the Rott sequence, also in Voerendaal (NL) and Eschweiler (DE), in the middle of the LRG, swarm activity occurred. In this contribution we discuss swarm catalogue and statistics, waveform cross-correlation and relocation, focal mechanism and crustal stress pattern, intensity distribution of the largest events, and potential swarm causality and its link with LRG faults.  The magnitude-frequency distribution of the Rott sequence indicates a completeness magnitude between ML=0.2 and ML=0.7, with corresponding estimated Gutenberg-Richter b-values of ~0.7 and ~1.0, respectively. These low b-values are typical of swarms with a tectonic origin. Focal depths are mostly between 8 and 11 km (1-sigma location uncertainty). Epicenters are located 2 - 4 km east of the Laurensberg fault, a secondary LRG fault parallel to the main graben faults with documented throw of Cretaceous strata and present-day morphology to the west. However, the dip direction and dip angle are not well known, and it is possible that the observed throw reflects Late Cretaceous inversion. In that case, the Laurensberg fault, which should currently have extensional kinematics similar to the other faults in the LRG, may well dip eastward and could potentially be related to the Rott sequence. If not, the causative structure remains unknown. This kind of seismotectonic analysis of low-magnitude tectonic swarms helps in locating and understanding seismogenic faults in stable continental regions in NW Europe. 
000005443 594__ $$aNO
000005443 6531_ $$aSeismic swarm
000005443 6531_ $$aRott sequence
000005443 6531_ $$aCross-correlation
000005443 6531_ $$aCollaboration
000005443 700__ $$aLecocq, Thomas
000005443 700__ $$aVanneste, Kris
000005443 700__ $$aLefevre, Marthe
000005443 700__ $$aCamelbeeck, Thierry
000005443 700__ $$aKnapmeyer-Endrun, Brigitte
000005443 700__ $$aCarrasco, Sebastian
000005443 700__ $$aKadmiel, Shahar
000005443 773__ $$t37th General Assembly of the European Seismological Commission, Corfu, Greece
000005443 8560_ $$fkoen.vannoten@observatoire.be
000005443 906__ $$aContributed
000005443 980__ $$aCTALKCONT