Inception of debris avalanches: remarks on geomechanical modelling

Debris avalanches are complex phenomena due to the variety of mechanisms that control the failure stage and the avalanche formation. Regarding these issues, in the literature, either field evidence or qualitative interpretations can be found while few experimental laboratory tests and rare examples of geomechanical modelling are available for technical and/or scientific purposes. As a contribution to the topic, the paper firstly highlights as the problem can be analysed referring to a unique mathematical framework from which different modelling approaches can be derived based on limit equilibrium method (LEM), finite element method (FEM), or smooth particle hydrodynamics (SPH). Potentialities and limitations of these approaches are then tested for a large study area where huge debris avalanches affected shallow deposits of pyroclastic soils (Sarno-Quindici, Southern Italy). The numerical results show that LEM as well as uncoupled and coupled stress–strain FEM analyses are able to individuate the major triggering mechanisms. On the other hand, coupled SPH analyses outline the relevance of erosion phenomena, which can modify the kinematic features of debris avalanches in their source areas, i.e. velocity, propagation patterns and later spreading of the unstable mass. As a whole, the obtained results encourage the application of the introduced approaches to further analyse real cases in order to enhance the current capability to forecast the inception of these dangerous phenomena.     

Rare earth elements absorption patterns in grapevine “<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.” cultivated in carbonate terrains (south-eastern Sicily,Italy)

Vitis vinifera L. vineyards grown on carbonate soil (Hyblean Plateau, SE Sicily) have been characterized in terms of rare earth elements (REEs) distribution. Results highlighted that the absorption of REEs by plants depends on the composition of the underlying soil, which in this case derives from limestone parent rock, allowing us to recognize the area of origin. Indeed, even slight differences in REEs content in soils may affect the absorption pattern of each grapevine cultivar. Importantly, the various parts of the plants showed differences in REEs absorption; such REEs fractionation is particularly evident in the leaf and juice samples. In general, the uptake and concentrations of REEs in plant tissues may be related to many factors such as geographical, climatic and lithological features. This is also pointed out by the statistical investigation, which took into account either the grapevine variety or each part of the plant. By taking into consideration both the grape variety and the type of soil, the present “multi-elemental” approach aims to provide a useful geochemical tool for assessing the geographical origin of the production area of wine.     

A self-sufficient approach for GERB cloudy radiance detection

Geostationary Earth Radiation Budget (GERB) is the broadband radiometer onboard the Meteosat Second Generation (MSG) platform, launched at the end of August 2002 and still in commissioning phase. GERB data is planned to be used in many applications concerning Earth Radiation Budget (ERB) calculation. In order to evaluate the impact of clouds on ERB, a cloud detection is required and, at present, a cloud mask based on higher spatial and spectral resolution data acquired by Spinning Enhanced Visible and Infrared Imager (SEVIRI), the imager onboard the same MSG platform, is planned to be used in order to identify cloudy GERB soundings.As an alternative, a self-sufficient (only based on GERB data) method (OCA, the One-channel Cloudy-radiance-detection Approach) is proposed, as a time-saving and, probably, more suitable solution than the planned co-location approach.In this paper, preliminary results obtained by using several years of Meteosat data as well as GERB synthetic radiances (produced from Meteosat-7 observations) are presented. It is shown how results obtained by using GERB data alone can be comparable (and better in terms of number and spatial distribution of clear-sky GERB soundings identified) to the ones achieved if the co-location of a higher resolution cloud mask is used.