GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Analysis of the 1982-2016 seismicity of Aswan region (south Egypt) T.A. Stabile 1 , E.R. Fat-HeIbary 2 , V. Serlenga 1 , S. Panebianco 1,3 , P. Tizzani 4 , R. Castaldo 4 , L. Telesca 1 , E.M. El-Amin 2 , H. Ahmed 2 1 Consiglio Nazionale delle Ricerche (CNR-IMAA), Italy 2 Natonal Research Insttute of Astronomy and Geophysics, Egypt 3 Dipartmento di Fisica e Scienze della Terra, Università di Ferrara, Italy 4 Consiglio Nazionale delle Ricerche (CNR-IREA), Italy Lake Nasser is the Egypt's largest artfcial water reservoir flled behind the Aswan High Dam. In this area a prolonged reservoir induced seismicity has been observed since the November 1981 Ms 5.3 earthquake. The dynamic interplay between loading and unloading operatons at Lake Nasser, coupled with the increase of pore fuid pressure within the crustal rocks may lead the faults to go beyond the critcal stress for failure (Gahalaut and Hassoup, 2012; Telesca et al., 2017). In response to the seismic concerns and the need for secure reservoir management, a permanent seismic network was established in 1982. This initatve has contributed signifcantly to the accumulaton of an extensive seismological dataset. From an inital catalogue encompassing 7833 natural and reservoir-induced seismic events recorded in the Aswan region from 1982 to 2016, our objectve is to gain insights into the structure and triggering mechanisms of seismogenic faults within this complex tectonic system. To achieve this goal, we obtained a new 1-D velocity model of the area. Then, absolute and relatve high- resoluton earthquake locatons for 2562 events have been determined. This process has enabled us to refne the fault structure in the Aswan region and beter comprehend the spato-temporal evoluton of seismicity. Our analysis revealed previously unmapped fault strands along the Kalabsha fault system and in the Wadi Kalabsha embayment area, enhancing the understanding of fault distributon beyond the original seismic catalogue. The spato-temporal evoluton indicated an eastward migraton of seismicity with progressively shallower hypocentres, potentally linked to fuid migraton processes and increased pore pressure in the Wadi Kalabsha embayment area. The combinaton of fuid pore-pressure difusion and Coulomb stress variaton from reservoir loading may also explain the variable faultng styles observed along an NW-SE striking alignment east of the Seyal Fault. We verifed such hypothesis through a 3-D poroelastc simulaton within a Finite Element (FE) framework. Specifcally, we addressed both the tme-dependent poroelastc equaton and the linear elastc equaton, employing a multphysics approach through the use of the Comsol sofware package version 6.2.