GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Later on, Valensise et al. (2022) investgated in 3D the spatal relatonships among 18 known seismogenic faults and 1,651 wells drilled for gas exploitaton in the main hydrocarbon province of northern-central Italy, based on the same DISS and ViDEPI databases. Together these data comprise a unique dataset worldwide. They adopted a robust statstcal technique implemented in a GIS, and again found a signifcant antcorrelaton between the locaton of productve wells and that of the considered seismogenic faults, which are ofen overlain or encircled by unproductve wells. Their fndings led to the following conclusions: (a) over geological tme, earthquake ruptures encompassing much of the upper crust may cause gas to be lost to the atmosphere from the potental reservoir formatons; (b) reservoirs underlain by smaller or aseismic faults are more likely to be intact. This implies that the May 2012 shocks may simply have been the most recent events released by faults having a long earthquake history; and c) the limited seismic coupling observed by previous investgators does not just indicate difuse aseismic behavior, but rather suggests that about 50% of the large thrust faults occurring beneath the Po Plain hydrocarbon province slip consistently in an aseismic fashion; the remainder are fully coupled, and hence capable of generatng the largest possible earthquake allowed by their size. Recent works on the sources of the May 2012 Emilia earthquake suggested that stck–slip behaviour occurs only where previous tectonic histories caused high-stfness rocks (e.g., Triassic and Jurassic limestones and dolostones) to be uplifed and brought in contact across the fault plane, up to the characteristc 3–10 km depth of local upper crustal thrust faults (Bonini et al., 2014). These results, which are of inherently global relevance, have crucial implicatons for future hydrocarbon exploitaton; for the public acceptance of energy-related facilites in tectonically actve areas; and for or assessing the seismic–aseismic behaviour of large thrust faults, leading to a more accurate estmaton of the local seismic hazard. They also suggest that in earthquake-prone areas, any facility for natural gas, hydrogen or CO 2 storage should (a) be located away from proven seismogenic faults, and (b) take full advantage of depleted gas reservoirs: in itself, the pre- exploitaton performance of such reservoirs proves they can sustain the typical pressures of an intact gas-feld, and should be free from the risk of being damaged by a large earthquake.