Spatiotemporal Evolution of Land Subsidence in the Beijing Plain 2003–2015 Using Persistent Scatterer Interferometry (PSI) with Multi-Source SAR Data

Land subsidence is one of the most important geological hazards in Beijing, China, and its scope and magnitude have been growing rapidly over the past few decades, mainly due to long-term groundwater withdrawal. Interferometric Synthetic Aperture Radar (InSAR) has been used to monitor the deformation in Beijing, but there is a lack of analysis of the long-term spatiotemporal evolution of land subsidence. This study focused on detecting and characterizing spatiotemporal changes in subsidence in the Beijing Plain by using Persistent Scatterer Interferometry (PSI) and geographic spatial analysis. Land subsidence during 2003–2015 was monitored by using ENVISAT ASAR (2003–2010), RADARSAT-2 (2011–2015) and TerraSAR-X (2010–2015) images, with results that are consistent with independent leveling measurements. The radar-based deformation velocity ranged from −136.9 to +15.2 mm/year during 2003–2010, and −149.4 to +8.9 mm/year during 2011–2015 relative to the reference point. The main subsidence areas include Chaoyang, Tongzhou, Shunyi and Changping districts, where seven subsidence bowls were observed between 2003 and 2015. Equal Fan Analysis Method (EFAM) shows that the maximum extensive direction was eastward, with a growing speed of 11.30 km2/year. Areas of differential subsidence were mostly located at the boundaries of the seven subsidence bowls, as indicated by the subsidence rate slope. Notably, the area of greatest subsidence was generally consistent with the patterns of groundwater decline in the Beijing Plain

Railway deformation detected by DInSAR over active sinkholes in the Ebro Valley evaporite karst, Spain

Subsidence was measured for the first time on railway tracks in the central sector of Ebro Valley (NE Spain) using Differential Synthetic Aperture Radar Interferometry (DInSAR) techniques. This area is affected by evaporite karst and the analysed railway corridors traverse active sinkholes that produce deformations in these infrastructures. One of the railway tracks affected by slight settlements is the Madrid-Barcelona high-speed line, a form of transport infrastructure highly vulnerable to ground deformation processes. Our analysis based on DInSAR measurements and geomorphological surveys indicates that this line shows dissolution-induced subsidence and compaction of anthropogenic deposits (infills and embankments). Significant sinkhole-related subsidence was also measured by DInSAR techniques on the Castejón-Zaragoza conventional railway line. This study demonstrates that DInSAR velocity maps, coupled with detailed geomorphological surveys, may help in the identification of the railway track sections that are affected by active subsidence

InSAR as a tool for monitoring hydropower projects: A review

This paper provides a review of using Interferometric Synthetic Aperture Radar (InSAR), a microwave remote sensing technique, for deformation monitoring of hydroelectric power projects, a critical infrastructure that requires consistent and reliable monitoring. Almost all major dams around the world were built for the generation of hydropower. InSAR can enhance dam safety by providing timely settlement measurements at high spatial-resolution. This paper provides a holistic view of different InSAR deformation monitoring techniques such as Differential Synthetic Aperture Radar Interferometry (DInSAR), Ground-Based Synthetic Aperture Radar (GBInSAR), Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR), Multi-Temporal Interferometric Synthetic Aperture Radar (MTInSAR), Quasi-Persistent Scatterer Interferometric Synthetic Aperture Radar (QPSInSAR) and Small BAseline Subset (SBAS). PSInSAR, GBInSAR, MTInSAR, and DInSAR techniques were quite commonly used for deformation studies. These studies demonstrate the advantage of InSAR-based techniques over other conventional methods, which are laborious, costly, and sometimes unachievable. InSAR technology is also favoured for its capability to provide monitoring data at all times of day or night, in all-weather conditions, and particularly for wide areas with mm-scale precision. However, the method also has some disadvantages, such as the maximum deformation rate that can be monitored, and the location for monitoring cannot be dictated. Through this review, we aim to popularize InSAR technology to monitor the deformation of dams, which can also be used as an early warning method to prevent any unprecedented catastrophe. This study also discusses some case studies from southern India to demonstrate the capabilities of InSAR to indirectly monitor dam health

Satellite Monitoring of Railways using Interferometric Synthetic Aperture Radar (InSAR)

There is over 15,600 km of track in the Swedish railroad network. This network is vital for the transportation of people and goods across the country. It is important that this network is monitored and maintained to ensure good function and safety. A tool for monitoring and measuring ground deformation over a large area remotely with high frequency and accuracy was developed in recent decades. This tool is known as Interferometric Synthetic Aperture Radar (InSAR), and is used by researchers, geo-technicians, and engineers. The purpose of this study has been to evaluate the use and feasibility of the InSAR technique for track condition monitoring and compare it to conventional track condition monitoring techniques. Malmbanan, which is primarily used to transport iron-ore from mines in Sweden to the ports of Luleå, Sweden and Narvik, Norway, is used as a case study for this project; specifically, the section between Kiruna and Riksgränsen. Coordinate matching of measurements from the provided Persistent Scatterer Interferometry (PSI) InSAR data and Optram data from survey trains were performed. Then measured changes over different time spans within the two systems were overlapped and classified with different thresholds to see if there is correlation between the two systems. An extensive literature review was also conducted in order to gain an understanding of InSAR technologies and uses.The literature review showed that there is a large potential and a quickly growing number of applications of InSAR to monitor railways and other types of infrastructure, and that the tools and algorithms for this are being improved. The case study, on the other hand, shows that it can be difficult to directly compare measurement series from different tools, each working on different resolutions in terms of both time and space. InSAR is thus not about to replace techniques such as those behind Optram (using measurement trains). Instead, the approaches offer complementary perspectives, each highlighting different types of issues. We find that InSAR offers a good way to identify locations with settlements or other types of ground motions. Especially transition zones between settlements and more stable ground can be challenging from a maintenance point of view and can clearly be identified and monitored using InSAR. With the rollout of national InSAR-data, and the large increase in data accessibility, we see a considerable potential for future studies that apply the technique to the railway area

Multi-sensor synergy for persistent scatterer interferometry based ground subsidence monitoring

Ground subsidence is a common phenomenon which causes disturbances and damages on the Earth’s surface. Especially in urban areas, it poses risk to life and property. Establishing solutions for damage prevention requires knowledge of subsidence behavior over time and space, which entails the collection of geospatial information. The present work investigates the ground surface dynamics over a field of deep mining in Sondershausen, Germany based on multi-temporal Synthetic Aperture Radar (SAR) images. Deformation patterns are extracted by means of Persistent Scatterer Interferometry (PSI), a technique that exploits the spatio-temporal characteristics of interferometric signatures from persistent scatterers. Since the impact of subsidence on surface structures varies spatially, high-risk areas can only be identified when the subsidence profile is known. To model the geometry of the subsidence bowl, the present study extends the extracted point information to a surface of estimations by interpolation. Furthermore, by the synergistic usage of PS estimations from different satellite sensors, this research addresses the problem of undersampling in critical areas, which is a common limitation of the PSI approach. The methodology developed here estimates missing information, i.e. refines the initial model, by deformation map of a different sensor covering a different time interval. In order to extend the period of monitoring as well as to improve the spatial and temporal sampling, the ground subsidence in Sondershausen is monitored with a multi-sensor SAR dataset. The C- and L-band acquisitions of the sensors ERS-1/2 (1995–2005), Envisat-ASAR (2004–2010) and ALOS-PALSAR (2007–2010) are used to derive 15 years of subsidence information at the location of persistent scatterers. From a temporal viewpoint, the obtained deformation maps indicate a non-linearly decreasing trend of ground subsidence, which is consistent with the backfilling history of the mine. From a spatial viewpoint, the results suggest one major subsidence trough located in the urban area of Sondershausen and a minor one found in the nearby village of Großfurra. The PSI deformation maps and models are validated in reference to the available leveling measurements covering the site in Sondershausen. In general, the validation results suggest a good agreement between the PSI and surveying models with the normalized root-mean-square error (RMSE) lower than 0.11. However, some significant deviations of ERS estimations are also found for a critical region. In this area the absence of persistent scatterers contributes largely to the observed differences. Consequently, the spatial refinement by synergy is applied to this region. The integration of points from ASAR or PALSAR deformation maps result in an improvement in the modeled geometry of the subsidence trough. With this improvement the RMSE calculated for the ERS model is decreased from 0.061 to 0.054. The application demonstrates the synergistic potential of multi-sensor PSI analysis to improve the interpretation of ground subsidence characteristics and, thus, to increase the confidence of risk assessment.Absenkungen des Bodens stellen ein häufig auftretendes Phänomen dar. Diese Bodensenkungen verursachen Störungen und Schäden an der Erdoberfläche, die, insbesondere in urbanen Gebieten, Menschenleben gefährden und die bestehende Infrastruktur beschädigen können. Die Entwicklung von Lösungsansätzen zur Vermeidung von Schäden erfordert fundierte Kenntnisse über die räumliche und zeitliche Verteilung der Absenkungsbewegungen. Im Rahmen der vorliegenden Studie wurde die Dynamik der Bodenbewegungen über dem Salzabbaugebiet Sondershausen in Deutschland mittels Zeitserien von Synthetic Aperture Radar (SAR)-Aufnahmen untersucht. Zur Analyse der Zeitserien wurde das Verfahren der Persistent Scatterer Interferometry (PSI) eingesetzt. Diese Methode zur Extraktion der Bodendeformation basiert auf der Auswertung räumlicher und zeitlicher Charakteristika der interferometrischen Signaturen zeitlich stabiler Punktstreuer. Zur Bestimmung von Gebieten, die von den Bodensenkungen besonders stark betroffen sind, ist eine detailliertere Ermittlung der geometrischen Eigenschaften der Absenkung nötig, da die Oberflächenstrukturen entlang des Absenkungsprofiles variieren. Aufgrund dessen wurde in der vorliegenden Studie die punktweise gewonnene Information in die Flache extrapoliert, um eine räumliche Modellierung des Absenkungsbeckens zu ermöglichen. Zur genauen Vermessung von Absenkungen mittels PSI ist eine möglichst hohe räumliche und zeitliche Abtastrate anzustreben. Diese sind bei der Untersuchung eines Gebietes mithilfe eines einzelnen Radarsensors häufig nicht gewährleistet. Im Rahmen der vorliegenden Arbeit wird ein Lösungsansatz für diese Limitation vorgestellt, welcher auf der synergetischen Verschneidung von Deformationskarten mehrerer Radarsensoren basiert. Fehlende Messwerte in der ERS-Zeitreihe werden anhand von Punktstreuern in ASAR- und PALSAR-Szenen geschätzt. Die Bodenbewegungen im Gebiet Sondershausen wurden mithilfe von Daten verschiedener Radarsensoren beobachtet, um eine verbesserte räumliche und zeitliche Abtastrate zu erzielen. Hierzu wurden Aufnahmen der C- bzw. L-Band Sensoren ERS-1/2 (1995–2005), Envisat-ASAR (2004–2010) und ALOS-PALSAR (2007–2010) auf zeitlich stabile Punktstreuer untersucht. Die zeitliche Analyse der resultierenden Deformationskarten zeigt eine nicht-lineare Abnahme der Bodenabsenkungen. Dieses Verhalten steht im Einklang mit den rezenten Verfüllungsaktivitäten in der stillgelegten Mine. Die räumliche Auswertung der Daten deutet auf ein Absenkungsbecken im Stadtgebiet von Sondershausen hin. Ein weiteres, kleineres Becken konnte um die Siedlung Großfurra identifiziert werden. Sowohl die Deformationskarten als auch die abgeleiteten Modelle wurden einer umfangreichen Validierung anhand von Nivellement-Messungen unterzogen. Die Ergebnisse zeigen generell eine gute Übereinstimmung zwischen den PSI- und Bodenmessungen mit einem root-mean-square error (RMSE) von weniger als 0,11. Nur vereinzelt kommt es zu signifikanten Abweichungen, was insbesondere auf die ERS-Ergebnisse zutrifft. Dies lässt sich durch fehlende Punktstreuer in den aktiven Absenkungsbereichen während der ERS-Messungen begründen. Durch die Integration von Punkten aus den ASAR oder PALSAR-basierenden Deformationskarten konnte die Geometrie der Absenkungen verbessert werden. Der für das ERS-Modell ermittelte RMSE verringert sich auf diese Weise von 0,061 auf 0,054. Die vorliegende Anwendung zeigt das Synergiepotential multi-sensoraler Daten und Methoden verbesserten Interpretation von Bodenabsenkungen sowie zur genaueren Abschatzung und Bewertung von daraus resultierenden Risiken

Urban Deformation Monitoring using Persistent Scatterer Interferometry and SAR tomography

This book focuses on remote sensing for urban deformation monitoring. In particular, it highlights how deformation monitoring in urban areas can be carried out using Persistent Scatterer Interferometry (PSI) and Synthetic Aperture Radar (SAR) Tomography (TomoSAR). Several contributions show the capabilities of Interferometric SAR (InSAR) and PSI techniques for urban deformation monitoring. Some of them show the advantages of TomoSAR in un-mixing multiple scatterers for urban mapping and monitoring. This book is dedicated to the technical and scientific community interested in urban applications. It is useful for choosing the appropriate technique and gaining an assessment of the expected performance. The book will also be useful to researchers, as it provides information on the state-of-the-art and new trends in this fiel

A quasi-elastic aquifer deformational behavior: Madrid aquifer case study

The purpose of this paper is to analyze the quasi-elastic deformational behavior that has been induced by groundwater withdrawal of the Tertiary detrital aquifer of Madrid (Spain). The spatial and temporal evolution of ground surface displacement was estimated by processing two datasets of radar satellite images (SAR) using Persistent Scatterer Interferometry (PSI). The first SAR dataset was acquired between April 1992 and November 2000 by ERS-1 and ERS-2 satellites, and the second one by the ENVISAT satellite between August 2002 and September 2010. The spatial distribution of PSI measurements reveals that the magnitude of the displacement increases gradually towards the center of the well field area, where approximately 80 mm of maximum cumulated displacement is registered. The correlation analysis made between displacement and piezometric time series provides a correlation coefficient greater than 85% for all the wells. The elastic and inelastic components of measured displacements were separated, observing that the elastic component is, on average, more than 4 times the inelastic component for the studied period. Moreover, the hysteresis loops on the stress–strain plots indicate that the response is in the elastic range. These results demonstrate the quasi-elastic behavior of the aquifer. During the aquifer recovery phase ground surface uplift almost recovers from the subsidence experienced during the preceding extraction phase. Taking into account this unique aquifer system, a one dimensional elastic model was calibrated in the period 1997–2000. Subsequently, the model was used to predict the ground surface movements during the period 1992–2010. Modeled displacements were validated with PSI displacement measurements, exhibiting an error of 13% on average, related with the inelastic component of deformation occurring as a long-term trend in low permeability fine-grained units. This result further demonstrates the quasi-elastic deformational behavior of this unique aquifer system.This work was developed during Pablo Ezquerro research stay within the Geohazards InSAR laboratory and Modeling group of the Instituto Geológico y Minero de España in the framework of DORIS project (Ground Deformation Risk Scenarios: an Advanced Assessment Service) funded by the EC-GMES-FP7 initiative (Grant Agreement nº 242212). This work has been also supported by the Spanish Ministry of Science and Research (MICINN) under project TEC2011-28201-C02-02 and EU FEDER. Additional funding was obtained from Spanish Research Program through the project ESP2013-47780-C2-2-R

Advances in Remote Sensing-based Disaster Monitoring and Assessment

Remote sensing data and techniques have been widely used for disaster monitoring and assessment. In particular, recent advances in sensor technologies and artificial intelligence-based modeling are very promising for disaster monitoring and readying responses aimed at reducing the damage caused by disasters. This book contains eleven scientific papers that have studied novel approaches applied to a range of natural disasters such as forest fire, urban land subsidence, flood, and tropical cyclones