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Giorgetti, Claudia
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Giorgetti, Claudia
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- PublicationOpen Access3D geological reconstruction of the M. Vettore seismogenic fault system (Central Apennines, Italy): Cross-cutting relationship with the M. Sibillini thrust(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The 2016–2017 Amatrice-Norcia seismic sequence was triggered by the reactivation of a complex NNW-SSE trending, WSW-dipping normal fault system cross-cutting the Umbria-Marche fold and thrust belt near M. Vettore. This fault system produced clear and impressive co-seismic ruptures on normal faults in the hangingwall of the M. Sibillini thrust, whereas ruptures in the footwall were observed, but less clear. As a result, a strong controversy exists in the literature about the geometry of the seismogenic faults, their relationships with preexisting thrusts, and the location of normal-faulting rupture tips. In this work, we present a 3D geological model of the M. Vettore area located between the Castelluccio basin and the outcrop of the M. Sibillini thrust, where the most evident co-seismic ruptures have been observed. The model shows the relationship between the ruptured normal faults and the M. Sibillini thrust, and was constructed using a grid of 14 geological crosssections parallel and orthogonal to the main structural elements (i.e. normal faults and thrusts) down to a depth of 3 km. The model was built using reference structural surfaces, such as the top of the Early Cretaceous Maiolica Fm., the M. Sibillini thrust and the main seismogenic normal faults belonging to the M. Vettore fault system. The 3D model has allowed us to calculate the vertical cumulative throw distribution for the M. Vettore normal faults. The cumulative geological throw of ca. 1300 m across the normal faults in the proximity of the M. Sibillini thrust indicates that the seismogenic fault system continues into the footwall of the thrust, displacing it in the sub-surface. The results of this study provide important constraints on the cross-cutting relationships between active normal and pre-existing compressional structures in seismically active areas, contributing to a better definition of the faults segmentation, and the related seismic hazard.141 143 - PublicationOpen AccessSeismic Reflection Profiles and Subsurface Geology of the Area Interested by the 2016-2017 Earthquake Sequence (Central Italy)(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Starting from 24 August 2016, a long seismic sequence, including nine Mw > 5.0 earthquakes, struck a wide area of the Central Italy. A large amount of geological, geodetic, and seismological data envisages a complex system of NNW-SSE trending, seismogenic normal faults. These active tectonic structures are well known at the surface and consistent with previous seismotectonic studies. In order to improve the comprehension of the seismotectonic framework of this seismic sequence, we provide a novel reconstruction of the subsurface geology of the area close to the NorciaMw 6.5 mainshock (30 October 2016), based on previously unpublished seismic reflection profiles and available geological data. All the data have been synthesized along a 47 km long, WSW-ENE trending geological cross section, interpreted down to a depth of 12 km. Comparing the subsurface geological model with the available seismological data, we find that the majority of seismicity is confined within the sedimentary sequence and does not penetrate the underlying basement. The basement has been constrained at depths of 8 to 11 km and coincides with the cutoff of the seismicity. We have also traced the trajectories of the seismogenic normal faults activated during this seismic sequence, reconciling the high-angle (dip>65°) normal faults exposed at the surface, with their angle (dip < 50°) at hypocentral depths. The results of this study may be useful for better understanding the rheological properties of the seismogenic rock volume, as well as the coseismic deformations of the topographic surface observed by geodetic techniques and field mapping.99 43