Modeling Earthquake Dynamics and Fault Poromechanics in the BedrettoLab FEAR Project: Opportunities Challenges

Understanding earthquake initiation, propagation, and arrest is critical for mitigating seismic risks, yet these processes remain among the most complex natural phenomena to decipher. The ERC-Synergy project FEAR (Fault Activation and Earthquake Ruptures), conducted within the Bedretto Underground Laboratory for Geosciences and Geoenergy (BedrettoLab), offers a pioneering approach to investigate these intricate mechanics. Here, we highlight the unique challenges and opportunities presented by the FEAR project, with a particular focus on computational earthquake physics and its potential to enhance our understanding of fluid-induced seismic events on broadband seismic arrays. Located ~1.5 kilometers beneath the Swiss Alps, BedrettoLab provides an unparalleled setting for a detailed study of earthquake mechanics. The FEAR project utilizes this exceptional environment to induce and monitor small-scale seismic events. By employing hydraulic stimulation on selected faults near the BedrettoLab tunnel, the project aims to initiate and observe earthquakes of approximately magnitude ~1.0. These refined methods provide a controlled setting to study the intricate details of earthquake processes closely, offering a chance to push the boundaries of current understanding of earthquake physics. Central to the FEAR project is the development and testing of hydro-mechanical computational methods capable of replicating various injection protocols. These methods systematically test a range of constitutive laws that govern the evolution of fault friction, integrating insights from laboratory experiments with fully inertial elastodynamic modeling of earthquake processes. This approach allows us to investigate the poroelastic response of the rock mass, examining how seismic and aseismic slip interact in space and time, and assessing the dynamic evolution of pore-fluid pressure due to processes such as shear-induced dilatancy and compaction. Furthermore, we employ 3D dynamic rupture simulations to explore conditions controlling either self-arresting or run-away rupture. These simulations provide critical insights into wave spectrum and attenuation near BedrettoLab, enabling us to predict the peak ground velocity (PGV) of anticipated magnitude ~1 earthquakes. This innovative modeling approach represents a significant opportunity to advance our understanding of fault mechanics and the influence of fluid interactions. In conclusion, the FEAR project within BedrettoLab provides a unique and controlled environment to study the mechanics of earthquakes. The challenges posed by this research are matched by the significant opportunities it offers for advancing our understanding of seismic phenomena. By focusing on innovative modeling techniques and integrating multidisciplinary data, this project aims to shed light on the complex dynamics of fault activation and rupture, ultimately contributing to more accurate seismic hazard assessments and safer geoenergy practices.