Suchergebnisse

The systematic and widespread availability of cheap computing power and storage space, alongside the drastic improvement in data transmission and active sensor technologies, has triggered an increasing interest by scientific and government institutions in the use of satellite data. One of the most promising applications is to provide emergency management agencies with early warning systems for catastrophic natural events, in order to support decision making. The data used in this work are ground displacement records gathered via interferometric processing of satellite RADAR data. We provide a novel post-processing approach based on a Functional Data Analysis paradigm, and apply it to Santa Barbara mud volcano.

Abstract. We present a new post-processing methodology for the analysis of InSAR (Synthetic Aperture Radar Interferometry) multi-temporal measures, based on the temporal under-sampling of displacement time series, the identification of potential changes occurring during the monitoring period and, eventually, the classification of different deformation behaviours. The potentials of this approach for the analysis of geological processes were tested on the case study of Naro (Italy), specifically selected due to its geological setting and related ground instability of unknown causes that occurred in February 2005. The time series analysis of past (ERS1/2 descending data; 1992–2000) and current (RADARSAT-1 ascending data; 2003–2007) ground movements highlighted significant displacement rates (up to 6 mm yr−1) in 2003–2007, followed by a post-event stabilization. The deformational behaviours of instable areas involved in the 2005 event were also detected, clarifying typology and kinematics of ground instability. The urban sectors affected and unaffected by the event were finally mapped, consequently re-defining and enlarging the influenced area previously detected by field observations. Through the integration of InSAR data and conventional field surveys (i.e. geological, geomorphologic and geostructural campaigns), the causes of instability were finally attributed to tectonics.

Abstract. We combine on-site investigations with the interpretation of satellite Persistent Scatterers (PS) to analyse ground instability in the historic town of Agrigento, Italy. Geological and geomorphologic surveys, together with geostructural and kinematic analyses, depict the deformational patterns of the northwestern sector of the town, previously documented by extensive literature available for the neighbouring Valley of the Temples. The geological and geomorphologic maps are reconstructed by combining bibliographic studies, field surveys and aerial stereo-interpretation. ERS-1/2 PS data reveal deformation velocities up to 18–20 mm yr−1 in 1992–2000 over the Addolorata landslide, and a sudden motion of 1.6 cm over the Bishop's Seminary in 1999. RADARSAT-1 PS data highlight velocities of 3.0 mm yr−1 for St. Gerlando's Cathedral and reveals worsening of its structural instability since 2006. Ground instability of the town is controlled by low quality and high fracturing of the Agrigento formation rock masses, and the remarkable contrast between different mechanical behaviours of its calcarenite (brittle), silt and clay (plastic) facies. Slow landslides and widespread erosion are also recognised in the clays of the underlying Monte Narbone formation. Coexistence of these factors induces progressive retrogression of the edge of the Girgenti hill and damages the overlying historic buildings, whose stability and safe accessibility are nowadays almost compromised.

Abstract. The superimposition of geological formations with marked contrast in geotechnical properties presents one of the most critical environments for slope instability due to the different response of the materials to the applied disturbances. Moreover, the above-mentioned geological setting is often associated with high risk conditions, since many isolated rock slabs located at a higher altitude than the surrounding countryside have been sites of historical towns or buildings. The purpose of the present paper is to investigate the mechanisms determining instability in rock slabs overlying a soft substratum, with reference to two cultural heritage sites in Malta. Accurate investigations have been carried out to evaluate the geological, geotechnical and geomechanical properties together with the main geomorphological features of the soft clayey substratum and the overlying limestone rock mass. The main instability processes have thus been identified and investigated through kinematic analyses and numerical modeling, combined with a 1992–2001 Persistent Scatterers monitoring of ground displacements. The study constitutes the basis for the subsequent restoration works.