MED-SUV project: New results and ongoing activities of WP 5 - Task 5.1 Characterization of the threatening phenomena from space and ground

Abstract

The mitigation of volcanic hazard on an active volcano like Etna, Italy, requires an in-depth characterization of threatening phenomena from space and ground. To contribute to hazard mitigation efforts, the Task 5.1 of the European project "MED-SUV" (Grant Agreement n. 308665) has focused on phenomena such as cone-forming and lava flow emplacement, volcanic plume and eruptive products, degassing processes, and landslides, analysing their characteristics, duration and spatial dimension. Data mining tools have been made available to tackle a variety of classification and pattern recognition problems. Modelling and field experiments were also carried out on past and recent volcanic activity. In particular, test cases of past eruptions selected from the dataset of images, acquired by the "Etna NETVIS" since 2005, have been analysed with the aim of defining the geometry of lava flows for improving modelling and interpretation of lava flow emplacement. For the study of the volcanic plume and eruptive products, a relevant result was the development of a method of spatio-temporal integration of radar parameters measured in real-time to retrieve the total mass and flux of pyroclasts. To refine this method, a proxy proportional to the relative mass loading - correlated with the ash plume height - was derived. On-going research focuses on dynamic aspects of the explosive volcanic activity from short (second) to longer (cycles of eruptive episodes) time scales using continuous measurements of tephra reflectivity and velocity close to the source. In addition, to retrieve accurate DEMs and volumetric information of proximal products (tephra cones, lava flows) from multi-view photogrammetry, tests were carried out in July 2014. A field test on the three cones of Monti Silvestri (Etna) benefited from a drone infrared imagery. As a contribute to flank dynamics evaluation and hazard assessment, a landslide susceptibility map at 1:10.000 scale of the north-eastern flank of Mt. Etna was produced, covering 168 km2. The map covers the area of the transtensive Pernicana Fault system, encompassing a few documented mass movements and landslides. Among the semi-quantitative approaches proposed in the literature to obtain the regional distribution of potentially unstable slopes, the present research combines the Rock Engineering System (RES) methodology with parameter zonation mapping in a GIS environment. It was also traced the areal distribution of potentially unstable slopes based on a detailed, site-specific study of the factors predisposing for landslide. The data mining tools available in the framework of Task 5.1 of the MED-SUV project allow us to tackle pattern recognition problems with supervised or unsupervised classification, considering various measures of similarity. Recent applications concern seismic data, along with the petrographic composition of rock, and in-soil radon emission. Additional software was developed improving existing schemes of automatic alert based on volcanic tremor data, establishing a voting procedure where each seismic station contributes to the decision whether or not to flag a criticality. Improved visualization tools also allow us to represent on map the development in time of tremor characteristics at the permanent seismic stations located on the volcano. Finally, in mid-July 2014, an experiment was carried out at the summit of Etna, involving 40 researchers/technicians of different institutions from Italy, Germany, and France. During this experiment, we acquired multiparametric (geophysical, geochemical and volcanological) data on the degassing processes at the North-East Crater (NEC), as well as degassing and eruptive activity at an eruptive fissure (EF), opened on 5th July 2014 at the base of the NEC. Several kinds of studies are currently in progress: i) analyses of signals recorded by the permanent networks, in order to get a general framework in a long time period; ii) analyses of the explosions at the vents of EF recorded by microphones, seismometers and high-speed cameras, with the aim to investigate their inter-times and amplitude, the acoustic source location, the dynamics of the bomb ejections, as well as the explosion waveform variability; iii) the comparison among geochemical, thermal camera images and seismo-acoustic data in order to assess the partitioning of erupted mass flux between lava and pyroclasts, to compare the total erupted "solid" flux with the amount of degassed magma at EF and NEC as obtained from the SO2 flux, and to compare these measurements with the seismic and acoustic parameters.