Scattering and absorption imaging of a highly fractured fluid-filled seismogenetic volume in a region of slow deformation

Napolitano, Ferdinando; Siena, Luca De; Gervasi, A.; Guerra, I.; Scarpa, Roberto; Rocca, Mario La

doi:10.1016/j.gsf.2019.09.014

Cited by 31 publications

(32 citation statements)

References 42 publications

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“…In the hangingwall of the activated fault systems (western sector), our anisotropic evidence and the excess rate of seismicity during the sequence are indicative of countless fluid-saturated cracks. Napolitano et al (2020) through a study based on seismic scatter and absorption confirmed the presence of a highly fluid-filled micro-fractured seismogenic volume around the main activated structures during the swarm. Passarelli et al (2015) established that the temporal and spatial behavior of seismicity in the western sector follows prevalently a swarm-like consistent with a transient, external forcing.…”

Section: Seismogenesismentioning

confidence: 84%

“…These values allow us to suppose the presence of a complex diffusivity fluid system where fluids can migrate along a relatively high-permeability hydraulic path but cannot be gathered. The existence of this network of fractures and/or porous fluid-filled is also invoked, i. e, by Della Vedova et al (2001) to interpret the unusual low geothermal gradient of the region, by Barberi et al (2004) and Totaro et al (2014) to explain an high Vp/Vs value observed in the shallowest crust and by Napolitano et al (2020) to justify the scatter and absorption anomalies.…”

Section: Shear-wave Splittingmentioning

confidence: 92%

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The 2011–2014 Pollino Seismic Swarm: Complex Fault Systems Imaged by 1D Refined Location and Shear Wave Splitting Analysis at the Apennines–Calabrian Arc Boundary

et al. 2021

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In the years between 2011 and 2014, at the edge between the Apennines collapsing chain and the subducting Calabrian arc, intense seismic swarms occurred in the Pollino mountain belt. In this key region, <2.5 mm/yr of NE-trending extension is accommodated on an intricate network of normal faults, having almost the same direction as the mountain belt. The long-lasting seismic release consisted of different swarm episodes, where the strongest event coinciding with a ML 5.0 shock occurred in October 2012. This latter comes after a ML four nucleated in May 2012 and followed by aseismic slip episodes. In this study, we present accurate relocations for ∼6,000 earthquakes and shear-wave splitting analysis for ∼22,600 event-station pairs. The seismicity distribution delineates two main clusters around the major shocks: in the north-western area, where the ML 5.0 occurred, the hypocenters are localized in a ball-shaped volume of seismicity without defining any planar distribution, whilst in the eastern area, where the ML 4.3 nucleates, the hypocenters define several faults of a complex system of thrusts and back-thrusts. This different behavior is also imaged by the anisotropic parameters results: a strong variability of fast directions is observed in the western sector, while stable orientations are visible in the eastern cluster. This tectonic system possibly formed as a positive flower structure but as of today, it accommodates stress on normal faults. The deep structure imaged by refined locations is overall consistent with the complex fault system recently mapped at the surface and with patterns of crustal anisotropy depicting fractures alignment at depth. The possible reactivation of inherited structures supports the important role of the Pollino fault as a composite wrench fault system along which, in the lower Pleistocene, the southward retreat of the ionian slab was accommodated; in this contest, the inversion of the faults kinematics indicates a probable southward shift of the slab edge. This interpretation may help to comprehend the physical mechanisms behind the seismic swarms of the region and defining the seismic hazard of the Pollino range: nowadays a region of high seismic hazard although no strong earthquakes are present in the historical record.

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Section: Seismogenesismentioning

confidence: 84%

Section: Shear-wave Splittingmentioning

confidence: 92%

The 2011–2014 Pollino Seismic Swarm: Complex Fault Systems Imaged by 1D Refined Location and Shear Wave Splitting Analysis at the Apennines–Calabrian Arc Boundary

et al. 2021

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“…From using earthquake scaling relationships based on coseismic rupture-length, as the main computation parameter, the obtained magnitudes are in the range of 6.45 (Wells and Coppersmith 1994) to 6.8 (Wesnousky et al 2008;Leonard 2010) in the case of a complete rupture of the VCT fault. The result suggests that the most recent earthquakes that have affected the study area (2012 -Mw 5.2;1894 -Mw 5.1;1708 -Mw 5.8 andperhaps 1693 -Mw 5.6) have a source at ~ 8 km depth (Totaro et al 2015;Brozzetti et al 2017a;Napolitano et al 2020, Sketsiou et al, 2021. Thus, the seismic energy released is likely too low for an active fault set as well as not enough to be causative of the buried VCT ruptures detected.…”

Section: Seismic Hazard Implicationsmentioning

confidence: 89%

“…The VCT controls the distribution and thickness of the clastic fill basin (Middle Pleistocene-Holocene in age, according to Schiattarella et al 1994) that reaches the maximum thickness (> 30 m) in the western sector (VCT hanging wall, see boreholes stratigraphy at http://sgi2.isprambiente.it/mapviewer/) whereas is very thin (generally < 2-3 m) in the eastern one. The spatial relationships, at surface and depth, between the Quaternary fault segments, and the hypocenters of the re-located events of the 2010-2014 seismic activity (Totaro et al 2015;Brozzetti et al 2017a;Napolitano et al 2020Napolitano et al , 2021Pastori et al 2021) suggest that the VCT is a good candidate as a seismogenic source for the Mw 5.2 (2012, October 25) Mormanno mainshock. In addition, the analysis of the historical seismicity highlights that the epicenter of the Mw 5.5, 1708 earthquake (Rovida et al 2020) is located within the VCT hanging wall block, close to its northern termination, leading to hypothesize the possibility of a common seismogenic source with the Mormanno 2012 event.…”

Section: Tectonic Setting and Seismicitymentioning

confidence: 98%

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

Ercoli

Cirillo

Pauselli

et al. 2021

Preprint

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Abstract. With the aim of unveiling evidence of Late Quaternary faulting, a series of Ground Penetrating Radar (GPR) profiles were acquired across the Campotenese continental basin (Mt. Pollino region) in the southern Apennines active extensional belt (Italy). A set of forty-nine 300 MHz and 500 MHz GPR profiles, traced nearly perpendicular to a buried normal fault, were acquired and carefully processed through a customized workflow. The data interpretation allowed us to reconstruct a pseudo-3D model depicting the boundary between the Mesozoic bedrock and the sedimentary fill of the basin, which were in close proximity to the fault. Once reviewing and defining the GPR signature of faulting, we highlight in our data how near surface alluvial and colluvial sediments appear to be dislocated by a set of conjugate (west and east-dipping) discontinuities that penetrate inside the underlying Triassic dolostones. Close to the contact between the continental deposits and the bedrock, some buried scarps which offset wedge-shaped deposits are interpreted as coseismic ruptures, subsequently sealed by later deposits. Although the use of pseudo-3D GPR data implies more complexity linking the geophysical features among the radar images, we have reconstructed a reliable subsurface fault pattern, discriminating master faults and a series of secondary splays. We believe our contribution provides an improvement in the characterization of active faults in the study area which falls within the Pollino seismic gap and is considered potentially prone to severe surface faulting. Our aim is for our approach and workflow to be of inspiration for further studies in the region as well as for similar high seismic hazard areas characterized by scarcity of near-surface data.

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“…The VCT controls the distribution and thickness of the clastic fill basin (Middle Pleistocene-Holocene in age, according to Schiattarella et al, 1994) that reaches the maximum thickness (∼ 30 m) in the western sector (VCT hanging wall; see borehole stratigraphy at http://sgi2.isprambiente.it/ mapviewer/, last access: 11 June 2021). The spatial relationships, at surface and depth, between the Quaternary fault segments and the hypocenters of the re-located 2010-2014 seismic events (Totaro et al, 2015;Brozzetti et al, 2017a;Napolitano et al, 2020Napolitano et al, , 2021Pastori et al, 2021) suggest that the VCT is a good candidate as a seismogenic source for the M w 5.2 (25 October 2012) Mormanno earthquake, as well as for strong paleo-events.…”

Section: Tectonic Setting and Seismicitymentioning

confidence: 97%

Ground-penetrating radar signature of Quaternary faulting: a study from the Mt. Pollino region, southern Apennines, Italy

et al. 2021

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Abstract. With the aim of unveiling evidence of Late Quaternary faulting, a series of ground-penetrating radar (GPR) profiles were acquired across the southern portion of the Fosso della Valle–Campotenese normal fault (VCT), located at the Campotenese continental basin (Mt. Pollino region) in the southern Apennines active extensional belt (Italy). A set of 49 GPR profiles, traced nearly perpendicular to this normal fault, was acquired using 300 and 500 MHz antennas and carefully processed through a customized workflow. The data interpretation allowed us to reconstruct a pseudo-3D model depicting the boundary between the Mesozoic bedrock and the sedimentary fill of the basin, which were in close proximity to the fault. Once the GPR signature of faulting was reviewed and defined, we interpret near-surface alluvial and colluvial sediments dislocated by a set of conjugate (W- and E-dipping) discontinuities that penetrate inside the underlying Triassic dolostones. Close to the contact between the continental deposits and the bedrock, some buried scarps which offset wedge-shaped deposits are interpreted as coseismic ruptures, subsequently sealed by later deposits. Our pseudo-3D GPR dataset represented a good trade-off between a dense 3D-GPR volume and conventional 2D data, which normally requires a higher degree of subjectivity during the interpretation. We have thus reconstructed a reliable subsurface fault pattern, discriminating master faults and a series of secondary splays. This contribution better characterizes active Quaternary faults in an area which falls within the Pollino seismic gap and is considered prone to severe surface faulting. Our results encourage further research at the study site, whilst we also recommend our workflow for similar regions characterized by high seismic hazard and scarcity of near-surface geophysical data.

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Scattering and absorption imaging of a highly fractured fluid-filled seismogenetic volume in a region of slow deformation

Cited by 31 publications

References 42 publications

The 2011–2014 Pollino Seismic Swarm: Complex Fault Systems Imaged by 1D Refined Location and Shear Wave Splitting Analysis at the Apennines–Calabrian Arc Boundary

The 2011–2014 Pollino Seismic Swarm: Complex Fault Systems Imaged by 1D Refined Location and Shear Wave Splitting Analysis at the Apennines–Calabrian Arc Boundary

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

Ground-penetrating radar signature of Quaternary faulting: a study from the Mt. Pollino region, southern Apennines, Italy

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