Induced seismicity is a limiting factor for the development of Enhanced Geothermal Systems (EGS). Its causal mechanisms are not fully understood, especially those of post-injection seismicity. To better understand the mechanisms that induced seismicity in the controversial case of the Basel EGS (Switzerland), we perform coupled hydro-mechanical simulation of the plastic response of a discrete pre-existing fault network built on the basis of the monitored seismicity. Simulation results show that the faults located in the vicinity of the injection well fail during injection mainly triggered by pore pressure buildup. Poroelastic stressing, which may be stabilizing or destabilizing depending on the fault orientation, reaches further than pressure diffusion, having a greater effect on distant faults. After injection stops, poroelastic stress relaxation leads to the immediate rupture of previously stabilized faults. Shear-slip stress transfer, which also contributes to post-injection reactivation of distant faults, is enhanced in faults with slip-induced friction weakening.

Abstract. Fluid injection into geological formations for energy resource development frequently induces (micro)seismicity. If intensely shaking the ground, induced earthquakes may cause injuries and/or economic loss, with the consequence of jeopardizing the operation and future development of these geoenergy projects. To achieve an improved understanding of the causes of induced seismicity, develop forecasting tools, and manage the associated risks, a careful examination of seismic data from reported cases of induced seismicity and the parameters controlling them is necessary. However, these data are hardly gathered together and are time-consuming to collate as they come from different disciplines and sources. Here, we present a publicly available, multi-physical database of injection-induced seismicity (Kivi et al., 2022a; https://doi.org/10.20350/digitalCSIC/14813), sourced from an extensive review of published documents. Currently, it contains 158 datasets of induced seismicity driven by various subsurface energy-related applications worldwide. Each dataset covers a wide range of variables, delineating general site information, host rock properties, in situ geologic and tectonic conditions, fault characteristics, conducted field operations, and recorded seismic activities. We publish the database in flat-file formats (i.e., .xls and .csv tables) to facilitate its dissemination and utilization by geoscientists while keeping it ‎‎directly readable by computer codes for convenient data manipulation. The multi-disciplinary content of this database adds unique value to databases focusing only on seismicity data. In particular, the collected data aims at facilitating the understanding of the spatiotemporal occurrence of induced earthquakes, the diagnosing of potential triggering mechanisms, and the developing of scaling relations of maximum possible earthquake magnitudes and operational parameters. Conclusively, the database will boost research in seismic hazard forecasting and mitigation, paving the way for increasing contributions of geoenergy resources to meeting net-zero carbon emissions.