Using seismic attributes in seismotectonic research: an application to the Norcia <i>M</i><sub>w</sub> = 6.5 earthquake (30 October 2016) in central Italy

Abstract

Abstract. In seismotectonic studies, seismic reflection data are a powerful tool to unravel the complex deep architecture of active faults. Such tectonic structures are usually mapped at the surface through traditional geological surveying, whilst seismic reflection data may help to trace their continuation from the near surface down to hypocentral depths. On seismic reflection data, seismic attributes are commonly used by the oil and gas industry to aid exploration. In this study, we propose using seismic attributes in seismotectonic research for the first time. The study area is a geologically complex region of central Italy, struck during 2016–2017 by a long-lasting seismic sequence, including a Mw 6.5 main shock. Three vintage seismic reflection profiles are currently the only ones available at the regional scale across the epicentral zone. These represent a singular opportunity to attempt a seismic attribute analysis by running attributes like the “energy” and the “pseudo-relief”. Our results are critical, as they provide information on the relatively deep structural setting, mapping a prominent, high-amplitude regional reflector interpreted as the top of basement, which is an important rheological boundary. Complex patterns of high-angle discontinuities crossing the reflectors have also been identified by seismic attributes. These steeply dipping fabrics are interpreted as the expression of fault zones belonging to the active normal fault systems responsible for the seismicity of the region. Such peculiar seismic signatures of faulting are consistent with the principal geological and tectonic structures exposed at surface. In addition, we also provide convincing evidence of an important primary tectonic structure currently debated in the literature (the Norcia antithetic fault) as well as several buried secondary fault splays. This work demonstrates that seismic attribute analysis, even if used on low-quality vintage 2D data, may contribute to improving the subsurface geological interpretation in areas characterized by limited and/or low-quality subsurface data but with potentially high seismic hazard.

A Normal Faults System in the Monte Nerone area and its significance in the recent seismo-tectonic setting of the Northern Umbria-Marche Apennines (Italy)

“…Most authors agree with a extensional regime supported by seismic profiles, earthquake distribution, and focal mechanism (Chiarabba et al, 2015;Bignami et al, 2019;Iezzi et al, 2019;Improta et al, 2019;Scognamiglio et al, 2018;Boncio et al, 2010;Porreca et al, 2020;Ercoli et al, 2020;Gori et al, 2018).…”

“…The knowledge of the areas related to the recent events in central Italy in L'Aquila (2009) and Amatrice (2016) has been considerably furthered thanks to the strong research activities of numerous researchers and institutions. Much progress has subsequently been made in these areas where surface and deep geological knowledge has been reviewed and reinterpreted (Buttinelli et al, 2018;Scognamiglio et al, 2018;Bignami et al, 2019;Improta et al, 2019;Ercoli et al, 2020).…”

Reassessing the lithosphere: SeisDARE, an open-access seismic data repository

“…The ESCI-N3 depicted a Moho offset between the CIZ and the WALZ, and the southward subduction of the oceanic crust of the Bay of Biscay as a consequence of Alpine shortening (Martínez Catalán et al, 1995;Álvarez-Marrón et al, 1995aÁlvarez-Marrón et al, , b, 1996Ayarza et al, 1998Ayarza et al, , 2004. Furthermore, ESCI-N2 and ESCI-N4 revealed a crustal thickening beneath the highest summits of the Cantabrian Mountains which was interpreted as the northward subduction of the Iberian crust under this mountain range (Pulgar et al, 1995(Pulgar et al, , 1996Fernández-Viejo and Gallastegui, 2005).…”

“…Towards the WALZ, a stack of thrust sheets probably affecting Precambrian rocks is placed above a crustal-scale ramp dipping to the west (Pérez-Estaún et al, Ayarza et al, 1998;Pérez-Estaún et al, 1997;Simancas et al, 2013); and (d) P-wave velocity model obtained from the wide-angle reflection data of RIFSIS and SIMA (simplified from Ayarza et al, 2014;Gil et al, 2014). , 1997Gallastegui et al, 1997;Fernández-Viejo and Gallastegui, 2005). The ESCI-N3 depicted a Moho offset between the CIZ and the WALZ, and the southward subduction of the oceanic crust of the Bay of Biscay as a consequence of Alpine shortening (Martínez Catalán et al, 1995;Álvarez-Marrón et al, 1995aÁlvarez-Marrón et al, , b, 1996Ayarza et al, 1998Ayarza et al, , 2004.…”

GPR signature of Quaternary faulting: a study from the Mt. Pollino region, southern Apennines, Italy

“…This seismic crisis occurred in an area displaced by an alignment of west-dipping Quaternary faults, where no important earthquakes had been recorded over the past 1500 years. Nine-strong and moderate seismic events struck a ~80 km long region, climaxing in the Mw = 6.5 "Norcia" mainshock (Porreca et al 2018 and references therein;Ercoli et al 2020), producing extensive surface faulting (Pucci et al 2017;Civico et al 2018;Villani et al 2018;Brozzetti et al 2019Brozzetti et al , 2020Testa et al 2019;Cirillo 2020). Geological and paleoseismological studies across the faults set were preceding this seismic sequence (Calamita et al 1992;Brozzetti and Lavecchia 1994;Barchi et al 2000;Galli 2003, Galli et al 2008).…”