The evolution of the Sciara del Fuoco subaerial slope during the 2007 Stromboli eruption: Relation between deformation processes and effusive activity

Focusing on the Island of Stromboli, this research investigates whether airborne remote sensing systems, such as those based on digital photogrammetry and laser scanner sensors, can be adopted to monitor slope deformation and lava emplacement processes in active volcanic areas. Thanks to the capability of extracting accurate topographic data and working on flexible time schedules, these methods can be used to constrain the regular and more frequent measurements derived from satellite observations. This work is dedicated to the monitoring of Stromboli's volcanic edifice which is beneficial when obtaining quantitative data on the geometry of deformation features and the displaced (failures and landslides) and emplaced (lava flows) volumes. In particular, we focus on the capability of extracting average effusion rates from volume measurements that can be used to validate or integrate satellite-derived estimates. Since 2001, a number of airborne remote sensing surveys, namely Digital Photogrammetry (DP) and Airborne Laser Scanning (ALS), have been carried out on Stromboli's volcano to obtain high resolution Digital Elevation Models (DEM) and orthophotos with sub-meter spatial resolution and a time schedule suitable for monitoring the morphological evolution of the surface during the quiescent phases. During the last two effusive eruptions (2002–2003 and 2007) the surface modifications, created on the Sciara del Fuoco slope and on the crater area as a consequence of effusive activity, were quantified and monitored using the same methodologies. Thiswork, which is based on the results obtained from the multi-temporal quantitative analysis of the data collected from 2001 to 2007, mainly focuses on the 2007 eruption but also accounts for analogies and differences regarding the 2002–2003 event. The 2007 eruption on the Sciara del Fuoco slope from 27 February until 2 April, produced a compound lava field including a lava delta on the shoreline, discharging most of the lava into the sea. The comparison of the 2007 DEMs with a pre-eruption surface (2006 LIDAR survey) allowed for the evaluation of the total lava volume that accumulated on the subaerial slope while two syn-eruption DEMs were used to calculate the average effusion rates during the eruption. Since the evolution of a lava field produced during an eruption can be seen as a proxy for the magma intrusion mechanism, hypotheses are formulated on the connection between the lava discharge and the instabilities suffered by the slope

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)

Slope stability analysis by multi-temporal DEMs and 3D modelling: The 2002 and 2007 Stromboli landslide events

Natural hazard related to the volcanic activity represents a potential risk factor, particularly in the vicinity of human settlements. Besides to the risk related to the explosive and effusive activity, the instability of volcanic edifices may develop into large landslides often catastrophically destructive, as shown by the collapse of the northern flank of Mount St. Helens in 1980. A combined approach was applied to analyse slope failures that occurred at Stromboli volcano. SdF slope stability was evaluated by using high-resolution multi-temporal DTMMs and performing limit equilibrium stability analyses. High-resolution topographical data collected with remote sensing techniques and three-dimensional slope stability analysis play a key role in understanding instability mechanism and the related risks. Analyses carried out on the 2002–2003 and 2007 Stromboli eruptions, starting from high-resolution data acquired through airborne remote sensing surveys, permitted the estimation of the lava volumes emplaced on the SdF slope and contributed to the investigation of the link between magma emission and slope instabilities. Limit Equilibrium analyses were performed on the 2001 and 2007 3D models, in order to simulate the slope behavior before 2002-2003 landslide event and after the 2007 eruption. Stability analyses were conducted to understand the mechanisms that controlled the slope deformations which occurred shortly after the 2007 eruption onset, involving the upper part of slope. Limit equilibrium analyses applied to both cases yielded results which are congruent with observations and monitoring data. The results presented in this work undoubtedly indicate that hazard assessment for the island of Stromboli should take into account the fact that a new magma intrusion could lead to further destabilisation of the slope, which may be more significant than the one recently observed because it will affect an already disarranged deposit and fractured and loosened crater area. The two-pronged approach based on the analysis of 3D multi-temporal mapping datasets and on the application of LE methods contributed to better understanding volcano flank behaviour and to be prepared to undertake actions aimed at risk mitigation

Landslide risk and monitoring system for conservation of Vardzia monastery, Georgia

The present paper reports preliminary results of a feasibility project developed in cooperation with National Agency for Cultural Heritage Preservation of Georgia, aimed at envisaging the stability conditions of the slope-forming rocks of the Vardzia Monastery (rupestrian city cave in the south-western Georgia) and finalized to the implementation of a low impact monitoring systems together with long term mitigation/conservation policies. A field analysis was conducted to reconstruct geometry of the rock cliff, characteristics of discontinuities, main failure modes of potential unstable blocks, magnitude of phenomena and geom.-echanical parameters. Instability processes are the result of different combination of causative factors such as: lithology, frequency and orientation of discontinuities versus slope orientation, physical and mechanical characteristics of slope-forming materials, morphological and hydrological dynamics. The adoption of different survey techniques (e.g. 3D laser scanner, Ground Base Radar Interferometry) adopted together could be the best solution in the interdisciplinary field of Cultural Heritage preservation policies. © 2013 Taylor & Francis Group, London

Softening and swelling mechanism affecting south slope of Civita di Bagnoregio (VT)

Civita di Bagnoregio is a small village in Central Italy, located on the top of a hill and affected by landslides that are progressively reducing the urban area. The access consists of a pedestrian bridge that connects Bagnoregio municipality to the village. The south slope beneath the bridge, is involved by frequent instability phenomena. This work describes the analysis carried out and it aimed at the definitions of geological and geotechnical mechanism affecting the above mentioned slope. A geotechnical survey has been carried out. These surveys showed the presence of a superficial layer, resulting from the softening and swelling of underlying clay-silty strongly overconsolidated, responsible for the superficial landslide phenomena. A slope stability and a 3D laser scanner model has been carried out. The analysis demonstrates that a correct design for the landscape preservation and consolidation of unstable towns needs an understanding of triggering mechanism and geotechnical properties of the involved soils. © 2013 Taylor & Francis Group, London

Natural hazard affecting the Katskhi pillar monastery (Georgia)

The present work reports the main results of a preliminary assessment of the stability condition affecting the Katskhi Pillar Monastery in western Georgian. The research activities have been carried out with the support of National Agency for Cultural Heritage of Georgia in Tiblisi, following field survey activities conducted during May and December 2012. The field mission was aimed at the implementation of the following activities: (i) collection of preliminary geological, geomorphological and geomechanical data in order to define the main strength and deformation parameters; (ii) geodetic surveying with TLS techniques for the 3D model reconstruction of the site and collection of geometric data for future slope stability analyses; (iii) seismic survey with passive technique to achieve information about resonant frequency of the site; (iv) preliminary analysis of rock pillar stability; (v) monitoring project design for a full analysis on long-term risk assessment for the Katskhi pillar

Differential SAR Interferometry for surface monitoring of an Earth Dam

Surface monitoring of dams is commonly based on in situ topographic surveying, time consuming and characterized by some limitations in space coverage and frequency. More recent satellite-based technologies allow us to integrate and improve the monitoring capabilities provided by ground-based methods, thanks to their effectiveness to measure many persistent scatters acting as non-destructive control points. The availability of a large number of measurements point, distributed along the whole structure and characterized by millimetric accuracy for the displacement rate, can be profitably exploited for the calibration of numerical models simulating its behavior under stress conditions thus improving the capability of maintaining safety standards. The aim of this work is to show how DInSAR (Differential Synthetic Aperture Radar Interferometry) technique can be profitably exploited and effectively integrated with the traditional monitoring systems, which provide comparable accuracy measurements on a limited number of points. Results on the test case study of Genzano di Lucania earth dam are discussed and presented

Automated geomatic system for monitoring historical buildings during tunneling in Roma, Italy

The present work is focused on the preliminary results obtained through the geomatic integrated monitoring system currently running at the test site of the Basilica of Maxentius in the Roman Forum. The system is aimed at controlling a number of archaeological sites which can be potentially affected by the tunneling works for a new metro line which is presently under construction. It includes different high precision geomatic sensors controlled by a centralized control station which continuously acquire data at high frequency. In order to identify a reliable processing procedure and assess the quality of the collected data, we started to develop and experiment a preliminary analysis of the data collected in the first period of the system operation (before the start of the excavation works). This activity allowed us to assess the performance of each sensor, focusing on the capability of the system to control also the stability of the monitoring stations. The obtained results will be adopted to better define an automated procedure for future massive data processing