GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 High-resoluton seismic depth imaging challenges across the 1980 (Ms 6.9) Southern Italy earthquake fault scarp at Pantano di S. Gregorio Magno (SA) G. Ferrara 1 , P.P. Bruno 1,2 , L. Improta 2 1 Dipartmento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli studi di Napoli ‘Federico II’, Napoli, Italy 2 Isttuto Nazionale di Geofsica e Vulcanologia, Roma, Italy  In this study, we present inital fndings and interpretatons derived from an high-resoluton seismic dataset, both 3D and 2D, obtained at Pantano di San Gregorio Magno (SA). The data were collected during two feld surveys, one in 2005 (the majority of the 2D lines, as detailed in Bruno et al., 2010) and another in 2022, as part of the TESIRA project (i.e., TEst Site IRpinia fAult; Bruno et al., 2023), a collaboratve efort involving Isttuto Nazionale di Geofsica e Vulcanologia (INGV) and Consiglio Nazionale delle Ricerche (CNR). The seismic surveys focused on the imaging of the basin across a surface scarp resultng from the Ms 6.9, 1980 Irpinia earthquake (Pantost & Valensise, 1990). Notably, pre-stack depth migraton (PSDM: see Yilmaz, 2001) is crucial for improving the accuracy of shallow seismic refecton images and the measured velocity distributon before stacking, partcularly in the presence of complex near-surface conditons (Bradford et al., 2006). However, a comprehensive understanding of the p-wave velocity distributon in the subsurface is crucial for this purpose. In this context, the efcacy of pre-stack migraton combined with full-waveform inversion could prove crucial in providing informaton to iteratvely enhance the velocity model and the associated seismic imaging of this complex environment. We show here the preliminary depth images resultng from pre-stack and post-stack depth migraton of the 2D profles and 3D volume. To enhance PSDM imaging through the refnement of the velocity model, we employed two distnct approaches within SeisSpace ProMAX®: the layer stripping method and the Deregowsky method. Both techniques utlize the Residual Move-Out (RMO) values picked from common image points. In certain instances, PSDM proved efectve in enhancing depth image quality compared to post-stack data. Conversely, due to the intricate near- surface conditons characterized by substantal lateral velocity variatons, post-stack migraton outperformed PSDM in some cases. This implies that our assessment of the background velocity model remains inaccurate. Even in this early phase of depth imaging, all seismic profles and the volume clearly depict the intricate splays associated with the 1980 Irpinia fault and its connectons to other actve segments of the Pantano San Gregorio Magno fault system. The tectonic infuence of these faults on basin development and sedimentaton is also evident.