GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Modeling dynamic ruptures on extended faults for microearthquakes induced by fuid injecton F. Mosconi 1 , E. Tint 1,2 , E. Casarot 2 , A. A. Gabriel 3 , R. Dorozhinskii 4 , L. Dal Zilio 5 , A. P. Rinaldi 5 , and M. Cocco 2 1 Università la Sapienza, Rome, Italy 2 Isttuto Nazionale di Geofsica e Vulcanologia, Rome, Italy 3 Scripps Insttuton of Oceanography, UC San Diego, La Jolla, CA 92093, USA 4 Technical University of Munich, Germany 5 Seismology and Geodynamics, Insttute of Geophysics, Department of Earth Sciences, Swiss Federal Insttute of Technology (ETH Zurich), Zurich, Switzerland Understanding the dynamics of microearthquakes is a tmely challenge to solve current paradoxes in earthquake mechanics, such as the stress drop and fracture energy scaling with seismic moment. Dynamic modeling of microearthquakes induced by fuid injecton is also relevant for studying rupture propagaton following a stmulated nucleaton. We study the main features of unstable dynamic ruptures caused by fuid injecton on a target pre-existng fault (50m x 50m) generatng a M w < 1 event. The selected fault is located in the Bedreto Underground Laboratory (Swiss Alps) at ≈1000m depth and these research actvites are performed in the framework of the ERC Synergy project FEAR (Fault Actvaton and Earthquake Ruptures). We perform fully dynamic rupture simulatons coupled with seismic wave propagaton in 3D by adoptng a linear slip- weakening fricton law. We use the distributed mult-GPU implementaton of SeisSol on the supercomputer Leonardo (CINECA). Stress feld and fault geometry are well constrained by in-situ characterizaton, allowing us to minimize the a priori imposed parameters. We investgate the dynamics of rupture propagaton and arrest for a target M w < 1 induced earthquake with spatally heterogeneous stress drops caused by pore pressure changes and diferent consttutve parameters (critcal slip-weakening distance, D c , dynamic fricton μ d ). We explore diferent homogeneous conditons of frictonal parameters, and we show that the spontaneous arrest of an unstable rupture is possible in the modeled stress regime (fg.1), by assuming a high rato between strength excess and dynamic stress drop (the fault strength parameter S), characterizing the fault before the pore pressure change. The rupture arrest of modeled induced earthquakes depends on the heterogeneity of dynamic parameters due to the spatally variable efectve normal stress, which controls the on fault G c spatal increment. Moreover, for a fault with high S values (low rupturing potental), small variatons of D c (≈0.45÷0.6 mm) can signifcantly impact on the fnal earthquake size, partcularly controlling the deceleraton and arrest phase. Studying dynamic interactons (stress transfer) among slipping points on the rupturing fault provides insights on the dynamic load and shear