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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. [ABSTRACT FROM AUTHOR]

A statistical approach was employed to model the spatial distribution of rainfall-triggered landslides in two areas in Sicily (Italy) that occurred during the winter of 2004–2005. The investigated areas are located within the Belice River basin and extend for 38.5 and 10.3 km 2 , respectively. A landslide inventory was established for both areas using two Google Earth images taken on October 25th 2004 and on March 18th 2005, to map slope failures activated or reactivated during this interval. Geographic Information Systems (GIS) were used to prepare 5 m grids of the dependent variables (absence/presence of landslide) and independent variables (lithology and 13 DEM-derivatives). Multivariate Adaptive Regression Splines (MARS) were applied to model landslide susceptibility whereas receiver operating characteristic (ROC) curves and the area under the ROC curve ( AUC ) were used to evaluate model performance. To evaluate the robustness of the whole procedure, we prepared 10 different samples of positive (landslide presence) and negative (landslide absence) cases for each area. Absences were selected through two different methods: (i) extraction from randomly distributed circles with a diameter corresponding to the mean width of the landslide source areas; and (ii) selection as randomly distributed individual grid cells. A comparison was also made between the predictive performances of models including and not including the lithology parameter. The models trained and tested on the same area demonstrated excellent to outstanding fit ( AUC > 0.8). On the other hand, predictive skill decreases when measured outside the calibration area, although most of the landslides occur where susceptibility is high and the overall model performance is acceptable ( AUC > 0.7). The results also showed that the accuracy of the landslide susceptibility models is higher when lithology is included in the statistical analysis. Models whose absences were selected using random circles showed a significantly better performance when learning and validation samples were extracted from the same area; whereas, conversely, no significant difference was observed when testing the models outside the training area. [ABSTRACT FROM AUTHOR]

Abstract: This work deals with an integrated geomorphological and chemical–physical study of “calanchi” landforms in two sites (Ottosalme and Catalfimo) of NW Sicily (southern Italy), developed on dominant silty-clay deposits. The calanchi fronts are characterized by different morphological features and dominant geomorphic processes. Sharp knife-edged ridges and concentrated water runoff dominate at Ottosalme, and smoother landforms affected by mass movements (mud flows and translational slides) prevail at Catalfimo. We focused on some geochemical and physical parameters such as pH, total dissolved salts, sodium adsorption ratio (SAR), porosity, plastic and liquid limits as possible causes of the above differences, with special emphasis on their role in discriminating the behavior of peculiar microforms, such as a weathered outer crust and the corresponding inner massive portion (unweathered substrate). Our results show that the main chemical–physical features of calanchi morphologies and microforms often display no clear correlations with respect to those reported in the existing literature, pointing to a higher complexity of patterns and behaviors. In particular, all samples consist of dispersive material (SAR values>10), but a more plastic and liquid behavior at Catalfimo can explain a higher occurrence of landslides and smoother morphology than at Ottosalme. Higher SAR values at Ottosalme well explain the dominance of concentrated water erosion. The chemical behavior of the studied microforms is better described by pH being alkaline with higher values in the inner substrate than the outer crust, and appears to minimize the effects of all other parameters and their responses to other external controlling factors. Lower SAR values in the crust suggest that clay dispersivity is not the prominent factor controlling its surface detachment and mobility downslope, which is more likely promoted by its higher porosity and consequent water absorption than the inner portion, with changes in the saturation state, shear strength and water pressure. [Copyright &y& Elsevier]