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Agnesi, Valerio
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Agnesi, Valerio
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- PublicationOpen AccessA Combined GNSS-DINSAR-IRT study for the characterization of a deep-seated gravitational slope deformation(2021-11-30)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Large deep-seated gravitational slope deformation (DsGSD) are slope instability phenomena affecting high relief-energy hillslopes and characterized by a high degree of complexity, enhanced also by wideness of the affected area and lithological heterogeneity. A combined approach based on different remote survey methodologies is herein presented with the aim of characterizing one of the most relevant DsGSDs in Sicily (Italy). The Scopello landslide involves the external margin of an overthrust plane, where a rigid carbonate tectonic unit overlies a ductile clayey substratum. The evidence of structural discontinuities crossing the rock masses and of unstable rock mass portions were pointed out by IRT, whose results were combined with the analysis of morphological features retrieved from a DTM, highlighting the presence of regional systems controlling the rock fracturing. Three GNSS surveys have been carried out in 2004 and 2005 on a 27-vertex geodetic network, attesting up to 20cm deformations caused by the triggering of landslides in the substratum. DInSAR results, obtained from the processing and interpretation of ENVISAT and Cosmo-SkyMed images, both in ascending and descending geometry for the time span 2002-2018, allowed evaluating the displacement rates over the area, highlighting that the movement is still active in its upper sector.43 6 - PublicationRestrictedA multidisciplinary approach to the evaluation of the mechanism that triggered the Cerda landslide (Sicily, Italy)(2005)
; ; ; ; ; ; ; ;Agnesi, V.; Dipartimento di Geologia e Geodesia, Universita` degli Studi, Corso Tukory 131, Palermo 90134, Italy ;Camarda, M.; Dipartimento CFTA, Universita` degli Studi, Via Archirafi 36, Palermo 90100, Italy ;Conoscenti, C.; Dipartimento di Geologia e Geodesia, Universita` degli Studi, Corso Tukory 131, Palermo 90134, Italy ;Di Maggio, C.; Dipartimento di Geologia e Geodesia, Universita` degli Studi, Corso Tukory 131, Palermo 90134, Italy ;Diliberto, I. S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Madonia, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Rotigliano, E.; Dipartimento di Geologia e Geodesia, Universita` degli Studi, Corso Tukory 131, Palermo 90134, Italy; ; ; ; ; ; The present paper describes a multidisciplinary approach to the evaluation of a seismically triggered landslide that occurred in the Cerda area (Italy) on September 6, 2002, about 1 h after an earthquake took place in the south Tyrrhenian Sea. The study was focused on an analysis of the role of the seismic input in triggering the landslide, in view of the evidence that no other mass movement was recorded in the adjacent areas despite geological and geomorphological spatial homogeneity. The studied area is located on a slope of the western flank of the Fiume Imera Settentrionale (Northern Sicily), which is made up of clayey–arenitic rocks. The slope inclines gently but is not uniform due to fluvial, gravitative, and rainwash processes. Field data dealing with global positioning system (GPS), geology, geomorphology, geophysics (vertical electrical sounding, or VES), and geochemistry (soil gas fluxes and composition) were acquired and analysed in order to investigate the cause–effect relationships between the earthquake and the mass movement. The GPS survey allowed us to map the ground failures that have also been classified on the basis of their kinematical meaning (i.e., compressive, distensive, or transcurrent structures). The geological analysis revealed outcropping rocks and tectonic structures. The geomorphologic survey highlighted the presence of preexisting landslide bodies. The geophysical survey detected a buried surface located at a depth of about 100 m . Finally, the geochemical survey showed that the gas released from the displaced mass came from a shallow depth and was not related to any active fault system. The abovementioned information allowed us to interpret the landslide event as a partial reactivation of a preexisting landslide body that was triggered by the earthquake.436 92 - PublicationRestrictedGPS Monitoring of the Scopello (Sicily, Italy) DGSD Phenomenon: Relationships Between Surficial and Deep-Seated Morphodynamics(Springer International Publishing Switzerland, 2015)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Scopello area, which is located along the north-western Tyrrhenian coastal sector of the Sicilian chain (Italy), is widely affected by Deep-seated Gravitational Slope Deformation (DGSD) phenomena, which are mainly the result of a geomorphologic setting marked by the outcropping of an overthrust plan, limiting a brittle fractured carbonate slab, laid onto a ductile marly-clayey substratum. Due to the very advanced stage of the deformation phenomena, a coupled morphodynamic style has established between shallow landslides and DGSD phenomena, affecting the exhumed ductile substratum and the overlaying rigid dismantled slab, respectively. A GPS network was realized for monitoring the Scopello landslide, consisting of 27 vertexes, which were directly cemented either onto rock or debris blocks or concrete structures rooted on the marly–clayey substratum. The geometry of the network and the geodetic technique adopted for the GPS signal acquisition allow the survey for a subcentimetric precision in the positioning of the vertexes. On February 2005 earth-flows and block/slab-slides movements affected the head sector of the landslide area. The displacements field, which was derived by comparing the results of a pre- (2004) and a post-event (2005) GPS surveys, is here analyzed and discussed. On the basis of the observed displacement, the connection between surficial and deeper ground deformations is confirmed.109 5