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Colella, Abner
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Colella, Abner
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- PublicationOpen AccessA Large Paleoearthquake in the Central Apennines, Italy, Recorded by the Collapse of a Cave Speleothem(2020-10)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Speleoseismological research carried out in the Central Apennines (Italy) contributed to understanding the behavior of active normal faults that are potentially able to generate Mw 6.5–7 earthquakes documented by paleoseismology and by historical and instrumental seismology. Radiometric (U‐Th, AMS‐14C, and bulk‐14C) dating of predeformation and postdeformation layers from collapsed speleothems found in Cola Cave indicates that at least three speleoseismic events occurred in the cave during the last ~12.5 ka and were ostensibly caused by seismic slip on one or more of the active faults located in the region surrounding the cave. We modeled the collapse of a tall (173 cm high) stalagmite to find a causative association of this event with one among the potential seismogenic sources. We defined the uniform hazard spectrum (UHS) for each seismogenic source at the site, and we used the calculated spectra in a deterministic approach to study the behavior of the speleothem, through a numerical finite element modeling (FEM). Although our analysis suggests the “Liri” fault as the most likely source responsible for the ground shaking recorded in the cave, the “Fucino” fault system, responsible for a Mw 7 earthquake in 1915, cannot be excluded as a potential source of speleoseismic damage. Results of this work provide new constraints on the seismotectonic history of this sector of Central Apennines and highlight the performance of integrated speleoseismological, seismic hazard, and numerical studies.106 64 - PublicationRestrictedGrain size and grain size distribution of a lithified fault core in carbonates rocks using multi-scale image analysis: The example of the San Benedetto-Gioia dei Marsi fault (Central Italy)(2020)
; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ;; Analyses of three oriented rock samples collected in the footwall of a major normal fault in Central Italy provide insights into textural properties of a lithified carbonate fault core. Data from lithified fault rocks are very rare and we document here the grain size distribution in a fault core at an unprecedented scale range, which complements already existing observations obtained from sieve, sedimentation and/or laser diffraction methods in loose deposits. X-ray powder diffraction analysis shows that the samples, which are located at a mutual distance of few tens of meters, are exclusively made of calcite. Mesoscopic samples and polished thin sections oriented normal to the fault plane have been analysed with high resolution scanner (HRS), transmission optical microscopy (TOM) and scanning electron microscopy in back-scattered mode (BS-SEM). Textural features of tectonised calcite crystals have been quantified using image analysis on digitalised photographs at magnifications from 1:1 to 9000:1, documenting size dimensions of grains from cm to sub-μm. The obtained D values have average values of 1.65 in 2D, overlapping with those independently obtained by box-counting methods in the core of the same fault by previous authors. Textures of calcite clasts in tectonised and lithified rocks can be appropriately quantified by the analytical protocols proposed here. This work represents the first multi-scale image analysis, from sub- μm to cm sizes, of the core portion of a normal fault that cut into carbonate rocks. Our study provides a template for similar investigations to be carried on other faults that will help to better understand the relations between fault textures and deformation processes.105 4