GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 A novel approach to earthquake source characterizaton using DAS strain rate data acquired along optcal fbres C. Strumia 1 , A. Trabatoni 2 , M. Supino 3 , M. Baillet 2 , D. Rivet 2 , G. Festa 1 1 Università di Napoli Federico II, Physics Department, Complesso Monte S. Angelo, Napoli, Italy. 2 Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, IRD, Géoazur. 3 Isttuto Nazionale di Geofsica e Vulcanologia, Osservatorio Nazionale Terremot, Roma, Italy. In recent years Distributed Acoustc Sensing (DAS) is establishing as a powerful tool in seismology, allowing for contnuous recordings of earthquakes, with unprecedented spatal sampling. DAS systems are interrogators connected to one end of an optcal fbre cable, sending repeated laser pulses, and exploitng measurements of phase variatons of the backscatered light with tme to infer measurements of the strain rate along the directon of the fbre (Hartog, 2017). The cable, interrogated by the DAS system, behaves as an almost contnuous array of single component seismic sensors. The availability of existng cables deployed for telecommunicaton purposes and the simplicity of DAS installaton opens up the possibility of investgatng harsh environments, where deployments of standard instruments could be expensive or unpractcal, such as glaciers, remote areas, sea botoms, volcanic fanks, or geothermal sites (e.g., Walter et al., 2020; Hudson et al.; 2021, Sladen et al., 2019; Current et al., 2021; Tsuji et al., 2021). These cables can reach lengths up to hundreds of kilometers and can depict the long-range contnuous, shallow propagaton of seismic waves when interrogated through DAS. The high potental of these systems has been nowadays exploited in several seismological tasks, from earthquake locaton (Piana Agostnet et al., 2022), subsurface characterizaton (Ajo-Franklin et al., 2019), focal mechanism inversion (Li et al., 2023a), tomography (Biondi et al., 2023), and source back projecton (Li et al., 2023b). Among the several seismological dutes, characterizing source parameters allows for interpretaton of the rupture process and its efects on the ground moton through the determinaton of its seismic moment and size. Unlike applicatons where only tme informaton is needed, consolidated methods based on spectral inversion for the determinaton of source parameters cannot be directly applied to DAS data, that natvely provide strain rate instead of acceleraton and/or velocity tme series. Using DAS amplitudes for earthquake source characterizaton leads to two possible alternatves: either convertng recordings to kinematc quanttes to apply existng physical models (Lior et al., 2021; 2023), or developing a novel forward modelling that directly digests DAS data. Despite conversion techniques have been proposed and validated (Trabatoni et al., 2023), moving to kinematc quanttes pollutes the spectral content of the data, especially at low