Ground deformation detection of the greater area of Thessaloniki (Northern Greece) using radar interferometry techniques

In the present study SAR interferometric techniques (stacking of conventional interferograms and Permanent Scatterers), using images from satellites ERS-1 and 2, have been applied to the region of Thessaloniki (northern Greece). The period covered by the images is 1992–2000. Both techniques gave good quantitative and qualitative results. The interferometric products were used to study ground surface deformation phenomena that could be related to the local tectonic context, the exploitation of underground water and sediments compaction. <br><br> The city of Thessaloniki shows relatively stable ground conditions. Subsidence in four locations, mainly in the area surrounding the city of Thessaloniki, has been detected and assessed. Two of the sites (Sindos-Kalochori and Langadhas) were already known from previous studies as subsiding areas, using ground base measurements. On the contrary the other two sites in the northern suburbs of Thessaloniki (Oreokastro) and in the south-east (airport area) were unknown as areas of subsidence. A further investigation based on fieldwork is needed in these two areas. Finally, an attempt to interpret the observed deformation, according to the geological regime of the area and its anthropogenic activities, has been carried out

Guidelines for the selection of appropriate remote sensing technologies for landslide detection, monitoring and rapid mapping: the experience of the SafeLand European Project.

New earth observation satellites, innovative airborne platforms and sensors, high precision laser scanners, and enhanced ground-based geophysical investigation tools are a few examples of the increasing diversity of remote sensing technologies used in landslide analysis. The use of advanced sensors and analysis methods can help to significantly increase our understanding of potentially hazardous areas and helps to reduce associated risk. However, the choice of the optimal technology, analysis method and observation strategy requires careful considerations of the landslide process in the local and regional context, and the advantages and limitations of each technique. Guidelines for the selection of the most suitable remote sensing technologies according to different landslide types, displacement velocities, observational scales and risk management strategies have been proposed. The guidelines are meant to aid operational decision making, and include information such as spatial resolution and coverage, data and processing costs, and maturity of the method. The guidelines target scientists and end-users in charge of risk management, from the detection to the monitoring and the rapid mapping of landslides. They are illustrated by recent innovative methodologies developed for the creation and updating of landslide inventory maps, for the construction of landslide deformation maps and for the quantification of hazard. The guidelines were compiled with contributions from experts on landslide remote sensing from 13 European institutions coming from 8 different countries. This work is presented within the framework of the SafeLand project funded by the European Commission’s FP7 Programme.JRC.H.7-Climate Risk Managemen

Monitoring pos-mining subsidence in the Nord-Pas-de-Calais coal basin (France). Comparaison between interferometric SAR results and levelling

International audienc

Synthetic Aperture Radar (SAR) Doppler Anomaly Detected During the 2010 Merapi (Java, Indonesia) Eruption

In this letter, we report the presence of a localized Doppler anomaly occurring during the focusing of a Radarsat-2 data set acquired on the Merapi volcano (Indonesia) during the devastating 2010 eruption. The Doppler anomaly is manifested as ∼3-km-wide bull’s-eye-shaped azimuth pixel shifts between two subaperture images. The Doppler anomaly is centered on the summit-south flank of the Merapi volcano. The pixel shifts reach up to 11.6 m. Since the Merapi volcano was undergoing a large eruption during the data acquisition, it is possible that there is a volcano-related phenomenon that has delayed the radar signal so much to create measurable pixel offsets within a single synthetic aperture radar (SAR) data set, similar, but more extensive, to the signal generated by targets motions; similar, but less extensive, to the signal generated by ionospheric perturbations. It is known that the SAR signal is delayed as it passes through heterogeneous layers of the atmosphere, but this delay typically affects the SAR signal to a fraction of the phase cycle or few centimeters depending on the radar wavelength employed by the system. We investigate the source of this anomalous metric signal; we review the theoretical basis of SAR image focusing, and we try to provide a consistent physical framework to our observations. Our results are compatible with the SAR signal being perturbed during the actual process of image focusing by the presence of a contrasting medium located approximately between 6- and 12.5-km altitude, which we propose being associated with the presence of volcanic ash plume

Procédé de régulation en température d'un système combinant une boucle fermée de régulation en température avec une boucle réalisée à partir d'une mesure de flux thermique

n° de priorité : FR20000000720 20000120 ; également publié en tant que : FR2804222 (B1) 2002-05-0

Measuring coseismic deformation on the northern segment of the Bam-Baravat escarpment associated with the 2003 Bam (Iran) earthquake, by correlation of very-high-resolution satellite imagery

International audienceThe role that the oblique reverse fault projecting to the surface at the Bam-Baravat escarpment (BBE) played in the slip accommodation of the 2003 (Mw 6.5) Bam earthquake is still unclear, regardless of many seismological and geodetic studies following this event. In this study, we correlate pre- and post-seismic very high spatial resolution panchromatic satellite images to map coseismic surface deformation along the northern segment of the BBE, a few hundred meters east of the urban area of Bam. Using a new approach based on principal component analysis (PCA) on offset measurements, we obtain 1.8 ± 0.6 cm east slip component and 2-6 ± 0.6 cm south slip component along the fault segment. Our results are consistent with ground observations over the study area and support the idea of the reactivation of the shallow part of this fault segment