Combining interferometric synthetic aperture radar (InSAR) data from ascending and descending orbits we estimate both quasi-vertical and quasi-east-west displacements for a region in central Algeria, ...an area encompassing an active large-scale carbon dioxide storage project, the In Salah gas storage project. The surface deformation associated with the injection into three horizontal wells is clearly visible in the InSAR estimates. We find that the addition of the quasi-horizontal displacement data enables us to discriminate between source models producing similar vertical displacements. In particular, predictions from a model consisting of a distribution of volume changes restricted to the reservoir depth interval satisfies the quasi-vertical data but does not match the quasi-east-west displacement data. However, aperture changes on subvertical damage zones, intersecting each of the injection wells, give rise to displacements matching both the quasi-east-west and vertical components. In all cases, we can match the observations with the most significant volume and aperture changes in regions immediately surrounding the injection wells.
Interferometric processing of series of data acquired over time by synthetic aperture radar (SAR) satellites makes it possible to measure millimetric deformations (typically due to landslides, ...subsidence and earthquake or volcanic phenomena) and to monitor the stability of terrain and infrastructures. Despite the unique capability to observe very large areas, this technology has been typically applied to the analysis of relatively small sites or specific geophysical phenomena. In this work, we present the first application of this technology to a national scale project, which required the processing, through advanced persistent scatterer interferometry (PSI) techniques, of about 20,000 SAR images acquired from 1992 to 2014 over the whole Italian territory by the ERS, Envisat, and COSMO-SkyMed satellites. The obtained results provide a huge database of surface deformation measurements covering the last 20years and the whole Italian territory, which represents an extremely useful and pioneering service for geo-hazards mapping and prevention.
•Millimetric ground deformation measurements over the whole Italian territory from 1992 to 2014•Monitoring of landslides, subsidence, and earthquake or volcanic phenomena•First application of synthetic aperture radar interferometry to national scale•Processed about 20,000 images acquired by ERS, Envisat and COSMO-SkyMed satellites
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Spaceborne differential radar interferometry has proven a remarkable potential for mapping ground deformation phenomena (e.g., urban subsidence, volcano dynamics, coseismic and postseismic ...displacements along faults, as well as slope instability). However, a full operational capability has not been achieved yet due to atmospheric disturbances and phase decorrelation phenomena. These drawbacks can often be-at least partially-overcome by carrying out measurements on a subset of image pixels corresponding to natural or artificial stable reflectors permanent scatterers (PS) and exploiting long temporal series of interferometric data. This approach allows one to push the measurement precision very close to its theoretical limit (in the order of /spl sim/1 mm for C-band European Remote Sensing (ERS)-like sensors). In this paper, the detection of both time-uniform and seasonal deformation phenomena is addressed, and a first assessment of the precision achievable by means of the PS Technique is discussed. Results highlighting deformation phenomena occurring in two test sites in California are reported (Fremont in the Southern Bay Area and San Jose in the Santa Clara Valley).
We measured ground displacements before and after the 2009 L'Aquila earthquake using multi-temporal InSAR techniques to identify seismic precursor signals. We estimated the ground deformation and its ...temporal evolution by exploiting a large dataset of SAR imagery that spans seventy-two months before and sixteen months after the mainshock. These satellite data show that up to 15 mm of subsidence occurred beginning three years before the mainshock. This deformation occurred within two Quaternary basins that are located close to the epicentral area and are filled with sediments hosting multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened. Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the carbonate hydrostructures and in the hydrologically connected multi-layer aquifers within the basins. This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were squeezed out. The pre-seismic ground displacements were then recovered because the groundwater table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed uplift.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The Carajás mineral province encompasses the world's largest iron reserves with excavation carried out through open pit benching. Mining operations in the area have significant areas of rock mass ...movements and surface displacements that potentially lead to slope instabilities with risks to personnel, equipment and production. Instabilities can be expected due to deep excavations in rock masses of low geomechanical quality, blasting practices and heavy precipitation. In this paper, ground instabilities are monitored through an integrated SAR analysis based on a data-stack of 33 TerraSAR-X images. This approach was designed to monitor distinct displacement regimes, ranging from small to high deformation rates, and to map surface changes, based on variations of radar reflectivity. Results were compared with field information (total station/prisms, ground based radar, geological and geomechanical maps), and the approach showed to be effective for monitoring ground deformation in the region. Due to its capabilities (synoptic view, high accuracy, dense grid sampling), the complementary use of space-based SAR with field monitoring systems proved to be strategic for operational mining planning and risk assessment in this challenging environment.
•An integrated SAR analysis to monitor stability in open pit iron mine is proposed.•Pit slopes and waste piles in Carajás iron complex were monitored using TerraSAR-X.•A-DInSAR was applied to monitor deformation regimes, from small to high rates.•Unwrapped interferograms, SqueeSAR™ and Speckle Tracking techniques were combined.•A-DInSAR results were validated by prism-monitoring and ground-based radar systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
AbstractThis study presents the results of spaceborne monitoring of two posttensioned bridges in Virginia. Routine safety inspections revealed extensive cracking in the concrete girders. Problems ...were traced to the inadequate quality of tendon grouting, resulting in the partially bonded condition. The TerraSAR-X radar satellite, operated by the German Aerospace Center, was used to acquire radar imagery in the Staring SpotLight mode from the ascending and descending orbits at 11-day intervals. The data were processed with the SqueeSAR algorithm, resulting in millimeter-range precision of the time-displacement series. No permanent deformations were detected at the posttensioned segments during the monitoring period of 1.3 years. The high density of the measurement points allowed adequate characterization of bridge displacements. The results of the interferometric analysis attest to the feasibility of implementing satellite-based performance monitoring of bridges, offering an innovative asset management tool that can complement and augment current inspection methods.
It has long been recognized that New Orleans is subsiding and is therefore susceptible to catastrophic flooding. Here we present a new subsidence map for the city, generated from space-based ...synthetic-aperture radar measurements, which reveals that parts of New Orleans underwent rapid subsidence in the three years before Hurricane Katrina struck in August 2005. One such area is next to the Mississippi River–Gulf Outlet (MRGO) canal, where levees failed during the peak storm surge: the map indicates that this weakness could be explained by subsidence of a metre or more since their construction.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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