The central Apennines are a fold-thrust belt currently affected by post-orogenic ex-tensional seismicity. To constrain the influ-ence that the inherited thrust-related struc-tures exert on the present seismic behavior of the belt, we provide the high-resolution structural and hydraulic characterization of one of the most external exposed thrust fault systems of the central Apennines, the Sibil-lini Mts. Thrust Front (STF). We integrate structural mapping, multiscale structural analysis, and in situ air permeability on the brittle structural facies of the thrust zone. We also performed K-Ar dating of selected fault rocks to better constrain structural in-heritance. The STF is defined by a complex, similar to 300-m-thick deformation zone involving Meso-Cenozoic marl and limestone that re-sults from the accommodation of both seis-mic and aseismic slip during shortening. Permeability measurements indicate that the low permeability (10-2 divided by 10-3 D) of the marly rich host rock diminishes within the thrust zone, where the principal slip surfaces and associated S-C structures represent efficient hydraulic barriers (permeability down to similar to 3 x 10-10 D) to sub-vertical fluid flow. Field data and K-Ar dating indicate that the STF began its evolution ca. 7 Ma (early Messin-ian). We suggest that the studied thrust zone may represent a barrier for the upward migration of deep fluids at the hypocentral depth of present-day extensional earth-quakes. We also speculate on the influence that similar deformation zones may have at depth on the overall regional seismotectonic pattern by causing transient fluid overpres-sures and, possibly, triggering cyclic exten-sional earthquakes on normal faults prone to slip while crosscutting the earlier thrust zones (as per a classic fault valve behavior). This mechanism may have controlled the ori-gin of the 2016-2017 central Apennines dev-astating earthquakes.
Architecture and permeability structure of the Sibillini Mts. Thrust and influence upon recent, extension-related seismicity in the central Apennines (Italy) through fault-valve behavior / Curzi, M; Cipriani, A; Aldega, L; Billi, A; Carminati, E; van der Lelij, R; Vignaroli, G; Viola, G. - In: GEOLOGICAL SOCIETY OF AMERICA BULLETIN. - ISSN 0016-7606. - (2023). [10.1130/B36616.1]
Architecture and permeability structure of the Sibillini Mts. Thrust and influence upon recent, extension-related seismicity in the central Apennines (Italy) through fault-valve behavior
Curzi, M
;Cipriani, A;Aldega, L;Billi, A;Carminati, E;Viola, G
2023
Abstract
The central Apennines are a fold-thrust belt currently affected by post-orogenic ex-tensional seismicity. To constrain the influ-ence that the inherited thrust-related struc-tures exert on the present seismic behavior of the belt, we provide the high-resolution structural and hydraulic characterization of one of the most external exposed thrust fault systems of the central Apennines, the Sibil-lini Mts. Thrust Front (STF). We integrate structural mapping, multiscale structural analysis, and in situ air permeability on the brittle structural facies of the thrust zone. We also performed K-Ar dating of selected fault rocks to better constrain structural in-heritance. The STF is defined by a complex, similar to 300-m-thick deformation zone involving Meso-Cenozoic marl and limestone that re-sults from the accommodation of both seis-mic and aseismic slip during shortening. Permeability measurements indicate that the low permeability (10-2 divided by 10-3 D) of the marly rich host rock diminishes within the thrust zone, where the principal slip surfaces and associated S-C structures represent efficient hydraulic barriers (permeability down to similar to 3 x 10-10 D) to sub-vertical fluid flow. Field data and K-Ar dating indicate that the STF began its evolution ca. 7 Ma (early Messin-ian). We suggest that the studied thrust zone may represent a barrier for the upward migration of deep fluids at the hypocentral depth of present-day extensional earth-quakes. We also speculate on the influence that similar deformation zones may have at depth on the overall regional seismotectonic pattern by causing transient fluid overpres-sures and, possibly, triggering cyclic exten-sional earthquakes on normal faults prone to slip while crosscutting the earlier thrust zones (as per a classic fault valve behavior). This mechanism may have controlled the ori-gin of the 2016-2017 central Apennines dev-astating earthquakes.File | Dimensione | Formato | |
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