Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

432 PATA Days 2024 be comprehensively assessed. Our study aims to create a thorough segmentation model for the eastern RGBF and evaluate the relative tectonic activity of each segment. Upper Rhine Graben activities The eastern Rhine Graben Boundary Fault (eastern RGBF) marks the eastern edge of the Upper Rhine Graben (Fig. 1). Despite the significant threat posed by seismic activity to the densely populated URG and its critical infrastructure, only a few studies have documented the paleoearthquake history and associated seismic hazard, with most research focusing on the western margin. Here, we present the results of the first paleoseismological trenching conducted on the eastern RGBF. We excavated six trenches near Ettlingen-Oberweier (south of Karlsruhe, Germany) on a secondary fault strand. The fault is near-vertical, transtensional left-lateral, and spreads into severalNNW-SSE en échelonbranches, forming a negative flower structure. Cross-cutting relationships, along with radiocarbon and Optically Stimulated Luminescence dating, reveal at least three surface-rupturing paleoearthquakes with moment magnitudes potentially around 6.5 ± 0.5. These events occurred from oldest to youngest: >56 kyrs (Ex), between 55 kyrs and 21 kyrs (Ey), and between 17 ka and 0.9 kyrs (Ez). However, the ages of these events are poorly constrained due to unconformities, which might conceal additional paleoearthquakes. Based on the cumulative vertical separation measured in trench T1 (1.2 ± 0.3 m), we calculate a vertical slip rate of 0.02 ± 0.005 mm/yr. Using a horizontally offset alluvial channel observed in electric resistivity tomography profiles (ERT) and scarp-parallel trenches, we infer a cumulative left-lateral slip of 5.9 ± 0.7 m and derive a horizontal slip rate of 0.1 ± 0.01 mm/yr. Considering both slip components, the average net slip rate is 0.1 ± 0.02 mm/yr over the past 59.5 ± 2.7 kyrs. Another study focuses on the southern segment of the Rhine River Fault (RRF) near the village of Tunsel, due to its striking geomorphological presence in the southwestern German landscape. The RRF is situated at the southern end of the URG and forms part of the eastern Rhine Graben Boundary Fault. We present detailed information about the timing of fault activity and the impact of earthquakes on the morphology, which is crucial for seismic hazard assessment, especially considering its proximity to the Fessenheim Nuclear Power Plant (NPP), located just 8 km away. By integrating sedimentary sequences, morphotectonic observations, shallow geophysics, and paleoseismological trenching, our findings reveal that several earthquakes along the RRF have ruptured the surface with magnitudes of M 6.7 ± 0.5. The most recent surface-rupturing earthquake occurred between 1044 - 1178 CE (Ez), and the penultimate event (Ey) is dated to the Younger Dryas (around 13 kyr BP) through stratigraphic correlation with reworked loess deposits. Three older earthquake events (Ex, Ew, and Ev) were also identified, occurring before the Late Glacial Maximum. Event Ex caused significant lateral spreading at the banks of the Pleistocene Rhine River. Vertical displacements reach up to 0.5 m and lateral offsets up to 1.5 m per earthquake event, consistent with approximately 15 - 30 km-long ruptures of this segment of the RRF. Lower Rhine Graben activities The Lower Rhine Graben (LRG) in Central Europe is another seismically active intra-plate regions and hosts damaging earthquakes in historical times (e.g., Düren 1756, Verviers 1692), all below M 7. The LRG is bounded to the west by the Feldbiss Fault Zone which has been intensively studied in the northern section during the last decades. Several research efforts have been undertaken to characterize the seismic hazard