Silvia Scifoni

Analysis of ground deformation using SBAS-DInSAR technique applied to COSMO-SkyMed images, the test case of Roma urban area

Differential Synthetic Aperture Radar Interferometry (DInSAR) represents a well-established remote sensing technique for the investigation of ground deformation phenomena.Among the DInSAR techniques, the Small BAseline Subset (SBAS) approach exploits ground surface at two mapping scales, low and high resolution, and allows the detection and monitoring of local deformation processes that may affect single buildings or man-made structures in urban areas. This work investigates the capability improvement of the SBAS-DInSAR technique to analyse deformation processes in urban areas by exploiting SAR data acquired by the Cosmo-SkyMed (CSM) constellation in comparison with the results obtained from data of first generation ERS/ENVISAT radar systems of he European Space Agency. In particular, we extracted mean deformation velocity maps as seen by the three different radar systems and, for each coherent pixel, we retrieved the corresponding displacement time series. Our analysis was focused on the Torrino area where independent studies had already revealed significant deformation signals testified by the serious damages on many buildings in the area. Moreover, in order to understand the causes of the CSM observed displacement rates, reaching few cm per year, we also performed a comparative analysis between DInSAR products and independent information derived from electrical resistivity tomography data and geological maps.

A multi-sensor approach for monitoring an active volcanic area: The 2011–2014 eruptive phase of Mount Etna

A multi-sensor approach has been adopted to investigate the summit area of Mount Etna that from January 2011 has significantly changed due to the intense volcanic activity from the New South East Crater. WorldView and Pleiades stereopairs were processed to obtain high resolution Digital Elevation Models and orthophotos used to update the topography of the volcano at over 3000 m of elevation. COSMO-SkyMed interferometric pairs provided additional data to attempt a reconstruction of the evolution of the New South East Crater between June 2011 and October 2014. The information retrieved from the optical and Synthetic Aperture Radar datasets were integrated with in-situ measurements and volcanological and geotechnical information thus contributing to the assessment of hazard scenarios.

Terrestrial laser scanning survey in support of unstable slopes analysis: the case of Vulcano Island (Italy)

The capability to measure at distance dense cloud of 3D point has improved the relevance of geomatic techniques to support risk assessment analysis related to slope instability. This work focuses on quantitative analyses carried out to evaluate the effects of potential failures in the Vulcano Island (Italy). Terrestrial laser scanning was adopted to reconstruct the geometry of investigated slopes that is required for the implementation of numerical modeling adopted to simulate runout areas. Structural and morphological elements, which influenced past instabilities or may be linked to new events, were identified on surface models based on ground surveying. Terrestrial laser scanning was adopted to generate detailed 3D models of subvertical slopes allowing to characterize the distribution and orientation of the rock discontinuities that affect instability mechanism caused by critical geometry. Methods for obtaining and analyzing 3D topographic data and to implement simulation analyses contributing to hazard and risk assessment are discussed for two case studies (Forgia Vecchia slope and Lentia rock walls).

The Use of Surveillance Cameras for the Rapid Mapping of Lava Flows: An Application to Mount Etna Volcano

In order to improve the observation capability in one of the most active volcanic areas in the world, Mt. Etna, we developed a processing method to use the surveillance cameras for a quasi real-time mapping of syn-eruptive processes. Following an evaluation of the current performance of the Etna permanent ground NEtwork of Thermal and Visible Sensors (Etna_NETVIS), its possible implementation and optimization was investigated to determine the locations of additional observation sites to be rapidly set up during emergencies. A tool was then devised to process time series of ground-acquired images and extract a coherent multi-temporal dataset of georeferenced map. The processed datasets can be used to extract 2D features such as evolution maps of active lava flows. The tool was validated on ad-hoc test fields and then adopted to map the evolution of two recent lava flows. The achievable accuracy (about three times the original pixel size) and the short processing time makes the tool suitable for rapidly assessing lava flow evolutions, especially in the case of recurrent eruptions, such as those of the 2011–2015 Etna activity. The tool can be used both in standard monitoring activities and during emergency phases (eventually improving the present network with additional mobile stations) when it is mandatory to carry out a quasi-real-time mapping to support civil protection actions. The developed tool could be integrated in the control room of the Osservatorio Etneo, thus enabling the Etna_NETVIS for mapping purposes and not only for video surveillance.

Satellite Techniques: New Perspectives for the Monitoring of Dams

Dam deformation detection, analysis, and monitoring represent a growing issue for a large part of commercial companies and research groups at national and international levels. Although dam failures are usually sudden, in the majority of cases it is possible to predict when structural damage conditions might become serious.

Stability Conditions and Evaluation of the Runout of a Potential Landslide at the Northern Flank of La Fossa Active Volcano, Italy

This paper focuses on the quantitative investigations carried out to evaluate stability conditions of the northern flank of the La Fossa cone (Vulcano Island) and the consequent runout of the debris avalanche that would be generated by a possible failure. The contribution describes first the geological setting and the typical instability phenomena of the area. Then it illustrates how the global morphology of the flank was reconstructed by combining aerial photogrammetry and high resolution 3D surveying techniques such as terrestrial laser scanner. The resulting digital elevation model (DEM) permitted us to extract and measure structural and morphological elements that drive and influence past and potential instabilities. These elements were used to constrain limit equilibrium analyses (LE) that were used to estimate the volume of soil mass susceptible of failure. Strength parameters at large scale were obtained from laboratory tests, described in previous studies, and back analyses of a past failure whose geometry was reconstructed from the DEM. Finally, results of runout analyses of the debris avalanche are presented and discussed. Analyses were conducted by using DAN-W and DAN-3D codes which allowed an estimate of the maximum runout distance and extension of the accumulation zone with respect to the inhabited area.

Monitoring an active volcanic area and mapping lava flows with multisource data: The case of Mount Etna from 2011 to 2015

The ground monitoring of an active volcanic area presents many complexities. By exploiting the remote sensing techniques, we developed an analytical methodology for observing and quantifying eruptive processes and the related phenomena (lava flows, volcanic avalanche/landslides, slope stability features). This methodology integrates HR optical images and SAR interferometry, acquired in different time frames and was tested on the case study of Mount Etna. The extraction of new cartographic products allows us to define the volcanic hazards that may impact on the surrounding populated areas and infrastructures.

Monitoring urban area by means of long term DInSAR time series

The work is focused on the exploitation of the results of a DInSAR analysis applied to ERS-ENVISAT and CSM data. The derived data are adopted to implement a multilevel analysis approach to investigate built-up areas at wide and local scales. The adopted analysis is aimed at performing: a territorial analysis to evaluate the distribution of large-scale deformation processes; an aggregated analysis applied at settlement scale to identify critical areas by providing building classification maps; a single structure damage assessment, using semi-quantitative and quantitative models to evaluate the stability of a structure and the potential damage scenarios.

Quantifying the effects of ground settlement on buildings by the exploitation of long term DINSAR time series: The case of Roma

Differential Synthetic Aperture Radar Interferometry (DInSAR) is a well-established remote sensing methodology aimed at the analysis and monitoring of displacements due to the ground settlement or to the deformations of the structures. Among the DInSAR techniques, the Small BAseline Subset (SBAS) approach, working at different scales of investigations, permits to detect and control the deformation processes that may involve structures and infrastructures in urban areas. This work is focused on the exploitation of the results obtained by applying Small Baseline Subset (SBAS) technique of high resolution DInSAR analysis applied to ENVISAT and COSMO-SkyMed data. The DInSAR products (average velocity maps and time series of displacements) are adopted to implement and test a processing architecture to investigate the stability of built-up areas at regional and local scales.

An integrated remote sensing approach for landslide susceptibly mapping at the volcanic islands of Vulcano and Lipari (Eolian Island, Italy)

Volcanic Island can be affected by instability phenomena such as landslide and partial collapse events, even in quiescent period. Starting from data collected by an aerial laser scanning survey at cm-level accuracy), a GIS based approach was implemented in order to perform a landslide-susceptibility analysis. The results of this analysis were compared and integrated with data derived from Differential Synthetic Aperture Radar Interferometry (DinSAR) analysis able to identify the most active areas and quantify the on-going deformation processes. The analysis is focused on the on the active volcanic edifice of Vulcano Island and in some areas of Lipari island, both include in the Eaolian Islands in Sicily (Italy). The developed approach represent a step-forward for the compilation of hazard maps furnishing in an overall contest, updated and georeferenced quantitative data, describing the morphology and the present behaviour of the slopes in the area of investigation.