GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 A natural pump-probe experiment reveals nonlinear elastc propertes along the Irpinia Fault, Southern Apennines N. D’Agostno 1 , S. Tarantno 1 , P. Poli 2 , M. Vassallo 1 , G. Ventafridda 3 , G. Festa 4 , A. Zollo 4 1 Isttuto Nazionale di Geofsica e Vulcanologia, Italy 2 Dipartmento di Geoscienze, Università di Padova, Italy 3 Acquedoto Pugliese SpA, Italy 4 Dipartmento di Fisica, Università di Napoli Federico II, Italy The conventonal picture of the earthquake cycle implies that rupture is reached by progressive stress buildup untl reaching fault’s failure strength. Alternatvely the failure strength may be altered by changes in pore pressure and/or propertes of fault rocks driven by hydrologically-driven strain/stress transients. This scenario may be associated with signifcant modifcatons of the elastc propertes of the crust potentally detectable with seismological tools. Natural oscillatory stress sources (tdes, seasonal and multannual hydrological stress variatons) can thus been exploited to probe the tme-dependent response of actve fault zones to stress variatons at various temporal and spatal scales and investgate tme-dependent variatons of its elastc propertes (Delorey et al., 2021). In the framework of the INGV Pianeta Dinamico project MYBURP (Modulaton of hYdrology on stress BUildup on the IRPinia Fault) a multdisciplinary (seismology, geodesy, geochemistry) study is carried out along the Irpinia Fault (Southern Apennines) to investgate the response of the crust to hydrological forcing associated to phases of recharge/ discharge of karst aquifers in terms of tme-dependent variatons of its elastc and hydraulic propertes . Charge/di scharge phases of the karst aqui fers in the Apennines cause signifcant seasonal and mult-annual strain transients (Silverii et al, 2019), that modulate the secular, tectonic deformaton (~3 mm/yr extension across the Apennines). It has been previously observed that these seasonal and mult-annual transients correlate with the seismicity rate (D’Agostno et al, 2018) and seismic velocity variatons (Poli et al., 2020). Recent studies (Silverii et al., 2016; D’Agostno et al., 2018) have shown the high sensitvity of the Irpinia Fault System (IFS) volume to hydrological stresses refected in a complex, tme-dependent response of deformaton and seismicity. We performed a natural pump-probe experiment to assess the non- linear behavior of the seismogenic volumes in response to non-tectonic deformatons. Seasonal horizontal strains associated with discharge and recharge of karst aquifers are used as the “pump”. Coda wave interferometry demonstrates to be a powerful tool to probe tme-dependent crustal