Analysis of thrust shear zones in curve-shaped belts: Deformation mode and timing of the Olevano-Antrodoco-Sibillini thrust (Central/Northern Apennines of Italy)

Calamita, Fernando; Satolli, Sara; Turtù, Antonio

doi:10.1016/j.jsg.2012.07.007

Cited by 32 publications

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“…We statistically investigated the relationships between rotations and structural trends in the OAS thrust front, by using structural data from this work (Figure ) and from Calamita et al . [; ], Piana [], and Di Domenica et al . [].…”

Section: Rotational Pattern Across the Oas Thrust Frontmentioning

confidence: 89%

“…Shortening has been inferred to be maximum in the arc apex and to progressively decrease toward the endpoints [ Pierantoni et al ., ]. A strong influence of inversion tectonics has been documented in the Northern Apennines [e.g., Argnani and Gamberi , ; Tozer et al ., ; Scisciani , ; Calamita et al ., ]: during the Pliocene, NNE‐SSW pre‐existing normal faults were reactivated as oblique thrust ramps with fault‐bend geometry, while NW‐SE‐oriented normal faults were passively displaced by the NNE‐SSW oblique and the NW‐SE frontal thrusts, with fault‐propagation shortcut anticlines development [ Calamita et al ., , ; Di Domenica et al ., ].…”

Section: Geological Backgroundmentioning

confidence: 99%

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Understanding progressive‐arc‐ and strike‐slip‐related rotations in curve‐shaped orogenic belts: The case of the Olevano‐Antrodoco‐Sibillini thrust (Northern Apennines, Italy)

et al. 2013

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We report on a paleomagnetic study of the southern sector of the Olevano‐Antrodoco‐Sibillini (OAS) thrust front, which corresponds to the southern limb of the Northern Apennines (Italy) orogenic salient. A lively debate has developed regarding the oroclinal/progressive‐arc versus non‐rotational nature of the OAS, which has been alternatively interpreted as a dextral strike‐slip fault, dextral transpressive fault, or frontal to oblique ramp that reactivated pre‐existing Jurassic normal faults. Here, we document the paleomagnetism, integrated with biostratigraphic and structural data, of 52 new sites from both the OAS hanging wall and footwall. On the basis of 39 retained sites, we find a peculiar pattern of tectonic rotations along the OAS thrust that evidences four rotational domains. The thrust footwall is characterized by a southern domain that undergoes an approximately 30° counterclockwise rotation with respect to the stable foreland, and an approximately non‐rotated domain. The data from the hanging wall indicate the occurrence of a dextral strike‐slip component along the southern sector of the OAS thrust supported by a strong clockwise rotation close to the NE‐SW lateral ramp, which rapidly fades 1 km from the thrust front. A slight but significant CW rotation observed in the remaining sites from the hanging wall confirms the progressive nature of the OAS, and its structural position as the southern limb of the Northern Apennines salient. Our detailed paleomagnetic study is crucial in discriminating between progressive‐arc‐ and strike‐slip‐related components in the main curved orogenic front of the Northern Apennines.

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Section: Rotational Pattern Across the Oas Thrust Frontmentioning

confidence: 89%

Section: Geological Backgroundmentioning

confidence: 99%

Understanding progressive‐arc‐ and strike‐slip‐related rotations in curve‐shaped orogenic belts: The case of the Olevano‐Antrodoco‐Sibillini thrust (Northern Apennines, Italy)

et al. 2013

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“…was interpreted as a transpressive thrust ramp resulting from tectonic inversion of a NNE‐SSW Jurassic normal fault system (i.e., the preorogenic Ancona‐Anzio fault; Castellarin et al, ; Calamita, Pace, et al, , and references therein; Di Domenica et al, ). This segment of the OAS shows a complex geometry: it is characterized by parallel splays defining a compound fault zone, up to 1 km wide; it presents fault‐bend folding structural style, with hanging‐wall ramp on footwall ramp relationships (Calamita, Satolli, et al, ).…”

Section: Tectonic Setting and Geological Observationsmentioning

confidence: 99%

Complex Fault Geometry and Rupture Dynamics of the M_W 6.5, 30 October 2016, Central Italy Earthquake

et al. 2018

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We study the 30 October 2016 Norcia earthquake (MW 6.5) to retrieve the rupture history by jointly inverting seismograms and coseismic Global Positioning System displacements obtained by dense local networks. The adopted fault geometry consists of a main normal fault striking N155° and dipping 47° belonging to the Mt. Vettore‐Mt. Bove fault system (VBFS) and a secondary fault plane striking N210° and dipping 36° to the NW. The coseismic rupture initiated on the VBFS and propagated with similar rupture velocity on both fault planes. Updip from the nucleation point, two main slip patches have been imaged on these fault segments, both characterized by similar peak‐slip values (~3 m) and rupture times (~3 s). After the breakage of the two main slip patches, coseismic rupture further propagated southeastward along the VBFS, rupturing again the same fault portion that slipped during the 24 August earthquake. The retrieved coseismic slip distribution is consistent with the observed surface breakages and the deformation pattern inferred from interferometric synthetic aperture radar measurements. Our results show that three different fault systems were activated during the 30 October earthquake. The composite rupture model inferred in this study provides evidences that also a deep portion of the NNE trending section of the Olevano‐Antrodoco‐Sibillini thrust broke coseismically, implying the kinematic inversion of a thrust ramp. The obtained rupture history indicates that in this sector of the Apennines, compressional structures inherited from past tectonics can alternatively segment boundaries of NW trending active normal faults or break coseismically during moderate‐to‐large magnitude earthquakes.

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“…It juxtaposes the carbonate thrust sheet of the Mts. Sibillini on the Laga Flysch, and its complex structure is related to a poly‐phased deformation involving inherited Mesozoic structures (Calamita et al, ; Di Domenica et al, ). The active normal faults are mostly NW trending and SW dipping, organized in subparallel and overstepping segments forming systems up to 25–30 km in length (Galadini & Galli, ; Roberts et al, ; Tondi & Cello, ).…”

Section: Introductionmentioning

confidence: 99%

Shear Wave Splitting Evidence and Relations With Stress Field and Major Faults From the “Amatrice‐Visso‐Norcia Seismic Sequence”

2019

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We present the largest dataset of anisotropic high‐quality parameters (~12,000) for the Amatrice‐Visso‐Norcia seismic sequence and investigate the physical mechanisms causing crustal anisotropy and its relation with crustal deformation, stress field, fluids, and earthquake generation. We performed shear wave splitting analysis on ~40,000 aftershocks recorded at 31 seismic stations during the first six months of the sequence following the 24 August 2016 Mw 6.0, Amatrice mainshock. Automatic and manual‐revised P‐ and S‐picking and high‐precision locations are used to delineate the fracturing pattern and spatio‐temporal variations in the anisotropic parameters: fast direction polarization (φ) and delay time (δt). The mean φ strikes N146°, parallel to the extensional Quaternary fault systems, and to the NW‐SE local active SHmax as proposed by the extensive dilatancy anisotropy model. Locally, φ directions outline the pattern of microscale and mesoscale structures that we relate to structural‐controlled anisotropy. Temporal variations of anisotropic parameters allowed us to deduce stress‐induced and pervasive fluid‐filled stress‐aligned crack systems as the prevalent anisotropic mechanisms in some sectors. Higher δt (>0.072 s) and higher anisotropy percentage (>1.5–2.0%) are found at the boundaries and in the western side of the activated fault systems, where heavily fractured carbonates are present. The fault network along with the lithological heterogeneities present in the area may act as a structural barrier along which fluids are channeled or trapped, thus causing overpressured fluid zones. Observations of shear‐wave splitting parameters during a seismic sequence can monitor the buildup of stress before earthquakes and the stress release as earthquakes occur.

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Analysis of thrust shear zones in curve-shaped belts: Deformation mode and timing of the Olevano-Antrodoco-Sibillini thrust (Central/Northern Apennines of Italy)

Cited by 32 publications

References 32 publications

Understanding progressive‐arc‐ and strike‐slip‐related rotations in curve‐shaped orogenic belts: The case of the Olevano‐Antrodoco‐Sibillini thrust (Northern Apennines, Italy)

Understanding progressive‐arc‐ and strike‐slip‐related rotations in curve‐shaped orogenic belts: The case of the Olevano‐Antrodoco‐Sibillini thrust (Northern Apennines, Italy)

Complex Fault Geometry and Rupture Dynamics of the M_W 6.5, 30 October 2016, Central Italy Earthquake

Shear Wave Splitting Evidence and Relations With Stress Field and Major Faults From the “Amatrice‐Visso‐Norcia Seismic Sequence”

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Analysis of thrust shear zones in curve-shaped belts: Deformation mode and timing of the Olevano-Antrodoco-Sibillini thrust (Central/Northern Apennines of Italy)

Cited by 32 publications

References 32 publications

Understanding progressive‐arc‐ and strike‐slip‐related rotations in curve‐shaped orogenic belts: The case of the Olevano‐Antrodoco‐Sibillini thrust (Northern Apennines, Italy)

Understanding progressive‐arc‐ and strike‐slip‐related rotations in curve‐shaped orogenic belts: The case of the Olevano‐Antrodoco‐Sibillini thrust (Northern Apennines, Italy)

Complex Fault Geometry and Rupture Dynamics of the MW 6.5, 30 October 2016, Central Italy Earthquake

Shear Wave Splitting Evidence and Relations With Stress Field and Major Faults From the “Amatrice‐Visso‐Norcia Seismic Sequence”

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Complex Fault Geometry and Rupture Dynamics of the M_W 6.5, 30 October 2016, Central Italy Earthquake