No abstract

Landslides interacting with large infrastructures represent a major problem for the economy, society as a whole, and the safety of workers. Continuous monitoring for 23 months using an integrated platform with a ground-based SAR interferometer (GB-InSAR), a weather station, and an automatic camera gave us the opportunity to analyze the response of an unstable slope to the different phases of work. The deformational behavior of both the natural slope and the man-made structures was recorded and interpreted in relation to the working stages and the rainfall conditions during the whole monitoring period. A typical pattern of displacement was identified for shallow landslides, debris produced by the excavation and gabions, metallic walls, and anchored bulkheads. Furthermore, insights into the dynamics and behavior of the slope and the man-made structures that interact with the landslide were obtained. Extreme rainfall is the main trigger of shallow landslides and gabion deformations, while anchored bulkheads are less influenced by rainfalls. Movement of debris that is produced by excavations and temporary metallic barrier deformation are closely related to each other. The herein proposed monitoring platform is very efficient in monitoring unstable slopes that are affected by human activities. Moreover, the recorded patterns of displacement in the slope and the man-made structures can be used as reference data for similar studies and engineering designs

Here we model quantitatively the stress and strain induced by tidal forces as possible triggers of Mount Etna eruptions during 1989, 2000 and 2001, by means of 2D numerical analysis by finite difference method applied to the volcano edifice. Spectral and vectorial analysis of tidal acceleration indicates that the quasi‐diurnal, semi‐diurnal and ter‐diurnal constituents may have induced decompressions up to some kPa in the shallow (i.e., 1,500 m) gas‐saturated magma reservoir, which controlled magma vesiculation and the timing of lava fountain activity from the South East Crater (SEC). We consider the geological heterogeneities in the volcanic edifice (i.e., rock geometries and properties, feeder conduit and vent systems, volcanic landforms), the magma properties (i.e., Bulk modulus, volatile content) and the ongoing volcano‐tectonic stresses (i.e., volcano flank deformations), which strongly influence the response of eruptive activity to tidal forces. Indeed, the tidal factor may act on flank deformation concomitant to shallow magma inflation. The implications of our model may help understand the eruptive behaviour and the disequilibrium state of the volcano and may be useful for hazard assessment at Mount Etna.

An extensive investigation of more than 90 landslides affecting a small river basin in Central Italy was performed by combining field surveys and remote sensing techniques. We thus defined the geomorphological setting of slope instability processes. Basic information, such as landslides mapping and landslides type definition, have been acquired thanks to geomorphological field investigations and multi-temporal aerial photos interpretation, while satellite SAR archive data (acquired by ERS and Envisat from 1992 to 2010) have been analyzed by means of A-DInSAR (Advanced Differential Interferometric Synthetic Aperture Radar) techniques to evaluate landslides past displacements patterns. Multi-temporal assessment of landslides state of activity has been performed basing on geomorphological evidence criteria and past ground displacement measurements obtained by A-DInSAR. This step has been performed by means of an activity matrix derived from information achieved thanks to double orbital geometry. Thanks to this approach we also achieved more detailed knowledge about the landslides kinematics in time and space.

No abstract

Abstract:In this work, the ability of advanced satellite interferometry to monitor pre-failure landslide behaviours and the potential application of this technique to Failure Forecasting Methods (FFMs) are analysed. Several limits affect the ability of the technique to monitor a landslide process, especially during the pre-failure phase (tertiary creep). In this study, two of the major limitations affecting the technique have been explored: (1) the low data sampling frequency and (2) the phase ambiguity constraints. We explored the time series of displacements for 56 monitored landslides inferred from the scientific literature and from different in situ and remote monitoring instruments (i.e., extensometers, inclinometers, distometers, Ground Base InSAR, and total station). Furthermore, four different forecasting techniques have been applied to the monitoring data of the selected landslides. To analyse the reliability of the FFMs based on the InSAR satellite data, the 56 time series have been sampled based on different satellite features, simulating the satellite revisit time and the phase ambiguity constraints. Our analysis shows that the satellite InSAR technique could be successful in monitoring the landslide's tertiary creep phase and, in some cases, for forecasting the corresponding time of failure using FFMs. However, the low data sampling frequency of the present satellite systems do not capture the necessary detail for the application of FFMs in actual risk management problems or for early warning purposes.

The study develops a geological/geotechnical model of the filling of the buried Tiber River valley in the area of Rome. The approach has been multidisciplinary: the fill sediments have been analysed in detail and are given on a cross section based on either the observations of 57 borehole cores and/or the laboratory tests on various types of samples. Information regarding the geology, geomorphology, climate, hydrographic network, urban development and history of the Rome area has been used to interpret this section and to extrapolate the data to the historical centre of Rome in order to formulate the model. The proposed model is a global forecasting rather than a detailed one and can be used as a starting point for projects to be conducted in the Tiber River alluvium or for defining a specific approach to technical problems linked to these projects

[1] An integrated numerical and geophysical approach was used to investigate the role of local seismic amplification in the reactivation of the Salcito landslide (Italy) after the Molise earthquake of 31 October 2002. Numerical stress-strain analysis with FLAC 5.0 FDM software, performed in dynamic configuration, showed that the 1 Hz frequency was consistent with landslide instability conditions. The Fourier spectrum of the triggering earthquake showed two main peaks occurring at 1 and 2 Hz, respectively, which could be related to local effects. The analysis of H/V spectral ratios of ambient noise records obtained in the landslide area, evidenced amplification effects in the 1-3 Hz range. On the basis of an engineering geology model, numerical modeling of both 1-D and 2-D seismic wave propagation was conducted using linear and nonlinear solutions. The simulation outputs showed (1) a 1 Hz amplification ascribable to 2-D effects due to a landslide mass lying within a basin-like geological structure; (2) a double-peak amplification at about 2 and 3 Hz, respectively, ascribable to 1-D resonance of the landslide mass; and (3) 1-D plus lateral wave effects within the landslide mass in the 2.5-3.5 Hz frequency range. These findings suggest that local amplification of ground motion by the Salcito landslide mass may generate a self-excitation process responsible for its reactivation.