Seismic reflection data in the Umbria Marche Region: limits and capabilities to unravel the subsurface structure in a seismically active area

Abstract

Before seismic data were made available, the subsurface setting of the Umbria-Marche area was mainly derived from the extrapolation of surface data and from models resulting from analogies with other mountain chains around the world. During the '90s industrial seismic data availability considerably increased, allowing the definition of new, previously unknown features. Beside the industrial seismic data availability, a deep crustal, near vertical seismic section trending E-W was acquired (CROP-03) across the Italian peninsula from the Tyrrhenian to the Adriatic coast. The subsurface data defined the compressional deformation style (thin-Vs thick-skinned) and the extensional deformation style. A set of east-dipping low-angle-normal faults, which dissect the previous compressional structures and which are the dominant features controlling the extension of the Apennines were recognised. The subsequent application of the seismic data interpretation to seismotectonic issues, defined in more detail the subsurface geometries of the active faults and the relationships between upper crust structure and seismicity.

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

“…This set of reflectors is interpreted as a high acoustic impedance contrast, possibly related to an important velocity inversion occurring between the Triassic evaporites (anhydrites and dolostones, V p ≈ 6 km s −1 ; e.g., Trippetta et al, 2010) and the underlying acoustic basement (metasedimentary rocks, V p ≈ 5 km s −1 ; sensu Bally et al, 1986). Comparable deep and prominent reflectors were also detected in other legacy data across adjacent regions of the Umbria-Marche Apennines (e.g., Barchi et al, 1998;Mirabella et al, 2008). This fact confirms its regional importance, particularly because it represents a lithological control indicating a seismicity cutoff (Chiaraluce et al, 2017;Mirabella et al, 2008;Porreca et al, 2018;Mancinelli et al, 2019).…”

“…2. The carbonate formations are next (Jurassic-Oligocene, about 2000 m thick, V av = 5800 m s −1 ), formed by pelagic limestones (Mirabella et al, 2008) with subordinated marly levels overlying an Early Jurassic carbonate platform (Calcare Massiccio Fm.). It outcrops mainly in the Umbria-Marche domain.…”

“…The data quality is extremely variable (medium to poor) with limited fold (generally <60 traces that are each common midpoints -CMPs), mainly due to environmental and logistical factors. Among the latter, we can list the different acquisition technologies, limited site access, the complex tectonic set-ting, and especially the different (and contrasting) outcropping lithologies (e.g., Mazzotti et al, 2000;Mirabella et al, 2008). The eastern area, showing higher data quality, consists of siliciclastic units of the Laga foredeep sequence, located at the footwall of the MSt.…”

“…This area presents ideal characteristics to test the application of seismic attributes as a new approach in seismotectonics. In the past, several seismic profiles were acquired in this region for hydrocarbon exploration and were later used to constrain subsurface geological structures (Bally et al, 1986;Barchi et al, 1991Barchi et al, , 1998Barchi et al, , 2009Ciaccio et al, 2005;Pauselli et al, 2006;Mirabella et al, 2008;Bigi et al, 2011). After the 2016-2017 seismic sequence, Porreca et al (2018) provided an updated regional geological model based on the interpretation of vintage seismic lines.…”

High‐Resolution Seismic Profiling in the Hanging Wall of the Southern Fault Section Ruptured During the 2016 Mw 6.5 Central Italy Earthquake

“…The substratum outcropping at the basin edges is made of Mesozoic-Tertiary marly limestones and cherts (Figures 1c and 2; Pierantoni et al, 2013). From a seismic imaging perspective, those generally thin-bedded layers have compressional velocity Vp ∼4,500-5,500 m/s and display internal reflectivity (Bigi et al, 2013;Latorre et al, 2016;Mirabella et al, 2008). However, the only seismic reflection profile crossing the area (labeled as NOR2; trace in Figure 2a) provides poor structural images of the topmost 2 km of the crust, and the Castelluccio basin is not resolved (e.g., Buttinelli et al, 2021;Ercoli et al, 2020;Porreca et al, 2018).…”