Using remote-dynamic earthquake triggering as a stress meter: identifying potentially susceptible faults in the Lower Rhine Embayment near Weisweiler, Germany

SUMMARY Transient stress changes from seismic waves of distant earthquakes can promote local fault slip, a phenomenon referred to as remote dynamic triggering. This study examines the remote triggering susceptibility of faults in the Lower Rhine Embayment (LRE) in the Weisweiler region, Germany, a proposed site for geothermal energy production. Assessment of remote triggering can guide industrial operations to assess seismic hazard and mitigate risks associated with fault reactivation caused by small stress perturbations. We select a set of 23 candidate mainshocks from global earthquake catalogues that produce peak ground velocities (PGVs) that exceed 0.02 cm s−1 in the LRE. The magnitude of these mainshocks ranges from 5.4 to 9.1, epicentral distances range from 50 to 12 ,300 km, and back azimuth ranges from 16$^{\circ }$ to 350$^{\circ }$ with a maximum azimuthal gap of 91$^{\circ }$. The candidate mainshocks generated PGVs locally from 0.02 to 0.28 cm s−1 (compared to typical threshold values ranging from 0.02 to 6 cm s−1), corresponding to dynamic stress ($\sigma _{\mathrm{ pd}}$) values of 1.4 to 26 kPa. We use P-statistics and waveform data from local seismic stations to identify seismicity rate changes and uncatalogued earthquakes that were potentially triggered by the passing mainshock waves. The analysis reveals a statistically significant increase in seismicity rates following four mainshocks: the 1992 M$_\mathrm{ w}$5.4 Roermond, Netherlands, 2021 M$_\mathrm{ w}$8.2 Chignik, Alsaka, USA, 2023 M$_\mathrm{ w}$7.6 Kahramanmaraş, Republic of Türkiye, and 2025 M$_\mathrm{ w}$8.8 Kamchatka, Russia earthquakes. The 1992 Roermond mainshock triggered earthquakes within 50 km of its epicentre that were clustered between the Feldbiss and Sandgewand faults. The same area experienced a triggered earthquake sequence following the Chignik mainshock, suggesting that future detailed monitoring in this area may be warranted. The Roermond aftershock distribution can be divided into two groups of events, including 61 that occur on the fault and in the near-field, which can be explained by static-stress increase and fluid diffusion. Another 32 remote aftershocks occurred that are consistent with secondary triggering promoted by aseismic slip propagation. The alignment of triggering mainshock back azimuths with the dominant strike direction of regional faults suggests that the orientation of incoming seismic waves is an important factor influencing susceptibility. Despite evidence of triggering, the majority of mainshocks (19 out of 23) were not followed by detectable seismicity-rate changes in the LRE, highlighting the complexity of conditions that lead to remote dynamic triggering. The study area does not respond to a triggering stress threshold, suggesting that nonlinear, or a combination of linear and nonlinear effects, dominate possible triggering mechanisms. Although the LRE does not respond to a clear triggering threshold, this study demonstrates that peak dynamic stress perturbations of approximately 1.4 kPa or greater can still trigger earthquakes. But, susceptibility is modulated by additional factors such as fault orientation, earthquake fault-zone properties, their state in the seismic cycle, and pre-existing stress state.