Analysis of a Subsidence Process by Integrating Geological and Hydrogeological Modelling with Satellite InSAR Data (original) (raw)
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—In this work, we exploit the integration of an advanced synthetic aperture radar (SAR) interferometry technique and the application of the finite-element method for the assessment and the interpretation of a localized subsidence phenomenon that took place within a specific area of Lisbon, Portugal. SAR images over the Lisbon city, covering different time intervals in the period of 1995–2010, were acquired and processed by means of the persistent scatterers (PSs) technique. Results clearly reveals a localized subsidence, limited to an area 2 km × 1.5 km wide, which has been confirmed by the leveling performed in 1976, 1996, and 2010. A physical interpretation of the observed ground deformations is provided based on the results of a finite-element model using stratigraphic data, in situ piezometric measurements, and geotechnical properties of the involved soils. The ground subsidence is interpreted as the consequence of a consolidation process affecting the central fine-grained soil layer, which in turn has been driven by water withdrawal from the existing aquifers. The change of the hydraulic boundary conditions was generated by the excavation works for the construction of underground lines and also by the reduction of rainfall water infiltration as an effect of the increase in ground surface impermeable areas due to urbanization. The consequent consolidation process of the compressible fine-grained soil layer is supposed to provide a reasonable explanation of the observed time series of ground displacement in the examined area. Index Terms—ENVISAT, ERS-1/2, FEM modeling, persistent scatterers (PSs), soil consolidation, subsidence, synthetic aperture radar interferometry (InSAR).
Remote Sensing of Environment, 2008
We applied the Interferometric Point Target Analysis (IPTA) technique to study the city of Rome (Italy) aiming to detect and measure the surface movements of buildings and urban structures. The available SAR dataset has been delivered by ESA CAT1 3258 and ranges the period 1992-2005. In particular ERS1-ERS2 data processed covers , while Envisat ASAR 2002. The Point Target velocity map shows a general stability except for some very local areas affected by subsidence rate larger than 10 mm/year. The analysis of the time series, compared to a detailed geological and geotechnical investigation of the lithostratigraphy of the alluvial sediments of the Tiber River, and combined with a temporal reconstruction of the expansion of the city over the alluvial valleys, allowed us to depict the main factors controlling the observed subsidence. These are: the in situ effective stress conditions, the related compressibility and viscous characteristics of the loaded soils, the thickness of the compressible stratum, the time since loading instant, and the entity of loading. Furthermore the observed subsidence is time-dependent, even at a long time-scale, with respect to the age of the buildings being most of the buildings constructed since the '50s still affected by slow subsidence. We mainly focused on the Grottaperfetta stream valley that is characterized by an anomalous high and time-lasting subsidence. Original data on the lithostratigraphic setting of this alluvial valley indicate that the high subsidence rate measured up to 2005 is caused by a still active primary consolidation process.
For several years, differential interferometry (DInSAR) using satellite radar images has proven its efficiency for the detection of vertical ground deformation with annual displacement rate measured by centimetres. In favourable cases, the classical technique provides measurements with a good precision (mm/yr) over large areas (100x100km) with typical ground resolution of 20m. Multiinterferogram techniques (stack interferometry and the recent method of Stable Points) lead to improved results. This presentation shows how DInSAR results can be integrated into a 3D geological model for first analysis of the cause of the detected phenomena. Based on a 3D geological model derived from bore holes, geological analysis and geostatistical tools, we discuss the relevance and characteristics of a linear settlement revealed on DInSAR products in the north of Lyon (France). This movement is localised along a known underground construction that occurred between 1994 and 1999: the underground motorway named TEO (Transversale Est-Ouest). The displacement is detected on radar images acquired between 1992 and 2000. The estimated annual line-of-sight component of the subsidence rate during this period is around-0.2cm/yr but the movement is at its maximum between May 1995 and March 1999, with a LOS subsidence rate then superior to-0.4cm/yr. It turns out that the deformation appears where TEO does not go through the granitic basement (or bedrock) layer.
International Journal of Applied Earth Observation and Geoinformation, 2019
This paper shows the results of the comparison between Multi-temporal Synthetic Aperture Radar (MTInSAR) products derived from different sensors (C-band ERS 1/2, Envisat, Sentinel-1 and X-band COSMO-SkyMed) and geotechnical data to investigate the driving factors of subsidence which affect a freight terminal located along the a coastal plain of Tuscany (central Italy). MTInSAR data have been acquired in a very long period, between 1992 and 2018 and were analyzed in terms of subsidence rates and deformation time series at building scale. The obtained results show that the oldest buildings are still affected by a deformation rate close to −5 mm/yr, whereas recent buildings register rates around −40 mm/yr. Time series of deformation suggest that the deformation rates decrease over time following time-dependent trend that approximates the typical consolidation curve for compressible soils. The geotechnical and stratigraphical analysis of the subsurface data (boreholes, cone penetration tests and dilatometer tests) highlights the presence of a 15 m thick layer formed of clay characterized by poor geotechnical characteristics. The comparison among InSAR data, subsurface geological framework and geotechnical reconstruction suggests a possible evaluation of the timing of the primary and secondary consolidation processes.
Landslides and Subsidence Assessment in the Crati Valley (Southern Italy) Using InSAR Data
Geosciences
In this work, we map surficial ground deformations that occurred during the years 2004-2010 in the Crati Valley (Southern Italy). The valley is in one of the most seismically active regions of the Italian peninsula, and presents slope instability and widespread landslide phenomena. We measured ground deformations by applying the small baseline subset (SBAS) technique, a multi-temporal synthetic aperture radar interferometry (InSAR) methodology that is used to process datasets of synthetic aperture radar (SAR) images. Ground displacements are only partially visible with the InSAR technique. Visibility depends on the geometry of the acquisition layout, such as the radar acquisition angle view, and the land use. These two factors determine the backscattering of the reflected signal. Most of the ground deformation detected by InSAR can be attributed to the gravitational mass movements of the hillslopes (i.e., landslides), and the subsidence of the quaternary deposits filling the valley. The movements observed along the valley slopes were compared with the available landslide catalog. We also identified another cause of movement in this area, i.e., ground subsidence due to the compaction of the quaternary deposits filling the valley. This compaction can be ascribed to various sources, such as urban population growth and sprawl, industrial water withdrawal, and tectonic activity.
This paper focuses on a multidisciplinary study carried out in an urban area affected by subsidence and related structural damages. The study area is located about 20 km east of Rome (Italy) and is characterised by relevant groundwater exploitation for various purposes as well as by the presence of compressible soils immediately below the ground level. Extensive processing at different scales of SAR satellite images (ERS and ENVISAT provided by ESA in the frame of a CAT-1 project) by means of A-DInSAR technique was performed. The time histories of ground displacements, have been analysed in combination with a detailed geological setting of the study area and with the hydrogeological changes occurred in the last decades (as the response to the anthropic stress) based on a large piezometric dataset. This comprehensive dataset allowed us to describe the space and time distributions of the subsidence process. The spatial pattern and deformation rate change is attributed to the following causes: i) the changes in the groundwater levels due to the intensification of mine exploitation (requiring dewatering operations) and ii) the distribution and thickness of recent compressible deposits. Specifically, it is derived that the groundwater level variations drive the timing of subsidence triggering over the area, whereas the local geological conditions control the magnitude of the deformation process.
Urban subsidence in the city of Prato (Italy) monitored by satellite radar interferometry
International Journal of Remote Sensing, 2003
Differential Synthetic Aperture Radar (SAR) interferometry has been widely used to monitor centimetric surface deformations in geophysical applications. In this letter, this technique is applied to study the displacement field in an urban area. A set of six European Remote Sensing satellite (ERS)-1/2 SAR images has been used to detect, map and quantify the subsidence occurring in the city of Prato near Florence (Italy). Four areas which have been affected by strong subsidence during the period 1993-2000 have been spotted within the city. The analysis of three interferograms processed from images taken two years apart shows that the deformation rate appears to be relatively constant, with a maximum value of about 8.3 cm y−1.
2013
Subsidence related to multiple natural and human-induced processes affects an increasing number of areas worldwide. Although this phenomenon may involve surface deformation with 3D displacement components, negative vertical movement, either progressive or episodic, tends to dominate. Over the last decades, differential SAR interferometry (DInSAR) has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas. This work discusses the main advantages and limitations of addressing active subsidence phenomena by means of DInSAR techniques from an end-user point of view. Special attention is paid to the spatial and temporal resolution, the precision of the measurements, and the usefulness of the data. The presented analysis is focused on DInSAR results exploitation of various ground subsidence phenomena (groundwater withdrawal, soil compaction, mining subsidence, evaporite dissolution subsidence, and volcanic deformation) with different displacement patterns in a selection of subsidence areas in Spain. Finally, a cost comparative study is performed for the different techniques applied.
Evaluating land subsidence by field survey and D-InSAR technique in Damaneh City, Iran
Journal of Arid Land
Based on the data from piezometers, well logs, geophysical surveys and the interferometric synthetic aperture radar (InSAR) technique, this study investigates the main causes of land subsidence in Damaneh City, Iran. The size, openings and direction of fissures were measured by micrometer and compass. The locations of fissures and wall cracks were determined by GPS. The geoelectrical data were used to determine the composition, thickness, depth and shape of lower parts of the aquifer. Groundwater fluctuations were evaluated by available piezometers. The InSAR technique was used to measure land deformation from space and to map the dense changes of surface displacements. The results indicate that the main cause of ground subsidence is the decline of groundwater heads and changes in composition and thickness of compressible lacustrine sediments. The subsidence map obtained from the radar data of ASAR sensor of ENVISAT satellite shows that the subsidence zone is mainly in northern city that is underlain by very thick fine sediments. The subsidence rates from March to December 2005 and from July 2011 to January 2012 are 6.7 and 7.0 cm/a, respectively. The results also show good correlations among the formation of earth features, decline in groundwater head and thickness of fine-grained sediments. We recommend that the groundwater withdrawal for agricultural and industrial sectors should be restricted and urban expansion in the northern part of the city should be constrained.