GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 elastc propertes. We computed seismic velocity variatons using empirical Green's functons reconstructed by autocorrelaton on contnuous 14-year-long tme series of ambient noise. We analyzed two diferent sites (co-located GPS and seismic statons), near and afar the IFS. We found that velocity variatons are signifcant ( ∼ 0.2%) nearby IF (shallow carbonates rocks), rather than far away from it. We compared the velocity variatons near IF with the tme series of Caposele spring discharge, temperature, horizontal deformaton and seismicity rate (computed thanks to dense geodetc and seismic networks). Our observatons are coherent at seasonal and mult-annual scales and can be explained with the same mechanism. At the tme of the maximum peak of the discharge spring, representng a proxy of the hydraulic head, the seismic wave velocity is minimum, the dilaton of crust is maximum and related to the opening of pre-existng cracks’ system. The background microseismicity occurrence is favored by the hydrologically-related dilataton, superimposed to the ongoing tectonic extension. From the comparison between hydrological strain variatons and velocity changes, we estmate a strain sensitvity of velocity change of ~-10^3 typical of worn crustal material and in good agreement with laboratory experiments. This non-linear elastcity regime suggests the presence of a mult-fractured and damaged crust subject to periodic seasonal phases of weakening/healing, potentally afectng earthquake nucleaton processes. References: D’Agostno, N. et al. Crustal Deformaton and Seismicity Modulated by Groundwater Recharge of Karst Aquifers (2018), Geophys Res Let 45, 10.1029/2018GL079794. Delorey, A. A., Guyer, R. A., Bokelmann, G. H. R. & Johnson, P. A. Probing the Damage Zone at Parkfeld (2021), Geophys Res Let 48, 10.1029/2021GL093518. Poli, P., Marguin, V., Wang, Q., D’Agostno, N. & Johnson, P. Seasonal and Coseismic Velocity Variaton in the Region of L’Aquila From Single Staton Measurements and Implicatons for Crustal Rheology (2020), J Geophys Res Solid Earth 125, 10.1029/2019JB019316. Silverii, F., D’Agostno, N., Métois, M., Fiorillo, F. & Ventafridda, G. (2016) Transient deformaton of karst aquifers due to seasonal and multyear groundwater variatons observed by GPS in southern Apennines (Italy). J Geophys Res Solid Earth 121, 10.1002/2016JB013361. Corresponding author: nicola.dagos tno@ingv.it