SAR Interferometry Data Exploitation for Infrastructure Monitoring Using GIS Application

Monitoring structural stability in urban areas and infrastructure networks is emerging as one of the dominant socio-economic issues for population security. The problem is accentuated by the age of the infrastructure because of increasing risks due to material deterioration and loss of load capacity. In this case, SAR satellite data are crucial to identify and assess the deteriorating conditions of civil infrastructures. The large amount of data available from SAR satellite sensors leads to the exploitation and development of new GIS-based procedures for rapid responses and decision making. In recent decades, the DInSAR technique has been used efficiently for the monitoring of structures, providing measurement points located on structures with millimeter precision. Our study has analyzed the behavior of structures in settlements, attempting to discuss the interactions of soil and structures, and examining the behavior of different types of structures, such as roads and buildings. The method used is based on long-term SAR interferometry data and a semi-automatic procedure to measure the displacement (mm/year) of structures, through a GIS-based application performed in the “Implemented MOnitoring DIsplacement” I.MODI platform. The analysis provides extensive information on long-term spatial and temporal continuity of up to 25 years of record, using satellite SAR multi-sensors from ERS, Envisat, and COSMO-SkyMed. The interpretation uses time series spatial analysis, supported by orthophotos, and layers of the DBTR (regional topographic database), Digital Surface model (DSM), and hydrogeological map to show anomalous areas with a high displacement rate and to observe the correlation of settlements in the sediments. With the satellite information and Geographic Information System (GIS), we were able to observe relevant parameters, such as the velocity of advance in the direction of the slope (deformation profiles), the cumulative displacement, and the trend changes in structures. The results illustrate an innovative procedure that allows the management of DInSAR data to facilitate the effective management of structures in which a monitoring protocol was developed at different spatial scales, integrating the information into a GIS

Exploitation of satellite A-DInSAR time series for detection, characterization and modelling of land subsidence

In the last two decades, advanced differential interferometric synthetic aperture radar (A-DInSAR) techniques have experienced significant developments, which are mainly related to (i) the progress of satellite SAR data acquired by new missions, such as COSMO-SkyMed and ESA’s Sentinel-1 constellations; and (ii) the development of novel processing algorithms. The improvements in A-DInSAR ground deformation time series need appropriate methodologies to analyse extremely large datasets which consist of huge amounts of measuring points and associated deformation histories with high temporal resolution. This work demonstrates A-DInSAR time series exploitation as valuable tool to support different problems in engineering geology such as detection, characterization and modelling of land subsidence mechanisms. The capabilities and suitability of A-DInSAR time series from an end-user point of view are presented and discussed through the analysis carried out for three test sites in Europe: the Oltrepo Pavese (Po Plain in Italy), the Alto Guadalentín (Spain) and the London Basin (United Kingdom). Principal component analysis has been performed for the datasets available for the three case histories, in order to extract the great potential contained in the A-DInSAR time serie

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

Satellite remote sensing and non-destructive testing methods for transport infrastructure monitoring: advances, challenges and perspectives

High temporal frequency monitoring of transport infrastructure is crucial to prioritise mainte-nance and prevent major service disruption or structural failures. Ground-based non-destructive testing (NDT) methods have been successfully applied for decades, reaching very high standards for data quality and accuracy. However, routine campaigns and long inspection times are re-quired for data collection and their implementation into reliable infrastructure management systems (IMSs). On the other hand, satellite remote sensing techniques, such as the Mul-ti-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) method, have proven effective in monitoring ground displacements of transport infrastructure (roads, railways and airfields) with a much higher temporal frequency of investigation and the capability to cover wider areas. Nevertheless, the integration of information from i) satellite remote sensing and ii) ground-based NDT methods is still a subject to be fully explored in civil engineering. This paper aims to review significant stand-alone and combined applications in these two areas of endeavour for transport infrastructure monitoring. Recent advances, main challenges and future perspectives arising from their mutual integration are also discussed

Differential Radar Interferometry Applied to the Detection and Monitoring of Geological Hazards

We live in a constantly changing environment, characterized by climate changes, extreme weather events and the occurrence of more frequent geological hazards that have a strong negative impact on the territory and society, interrupting services, damaging buildings and infrastructure and jeopardizing the life of millions of people worldwide. For this reason, there is the need to build a society resilient to natural-hazards, which can understand how the natural system behaves and responds to natural and human-induced modifications and can adapt to these changes. The monitoring of the territory is necessary to comprehend the triggering factors and the mechanisms of geological hazards and to plan the most suitable actions to prevent and mitigate the risk. The monitoring of geological hazards with conventional ground-based techniques such as Global Positioning System (GPS) and levelling is usually expensive and time consuming, which limits the number of measured points and the overall duration of the surveys. One of the best way to overcome to these problems is to use remote-sensing techniques to monitor large portion of territory reducing operating costs and time. Advanced Differential Synthetic Aperture Radar Interferometry (A-DInSAR) is one of the best tool to monitor and study ground displacements over very large portions of territory in a cost-effective way. In this Doctoral Thesis, we applied A-DInSAR to the monitoring of the geological instabilities occurring in different areas characterized by unique geological and environmental features. The selected areas include different environments such as vegetate territories, low and steep topography, coastal areas, salty deserts, urbanized land, each of them affected by hazards of natural and anthropic origin such as landslides, subsidence and karstic activity. In each case study, the monitoring activity presented its own challenges that were overcome adopting specific technical solutions in the data processing and management. The aim of this work is to give an overview of the potential of A-DInSAR techniques when applied to the study of geological hazards in different environments. This can be useful to show to local Authorities that A-DInSAR can be fully integrated as part of the activities carried out to manage the territory and to prevent and mitigate the risk related to geological hazards

Assessment of landslide susceptibility in Structurally Complex Formations by integration of different A-DInSAR techniques

Instability events are recurring phenomena in Southern Italy due to its geological history and tectonic-geomorphological evolution leading to the occurrence of several formations identified as Structurally Complex Formations (SCFs; Esu, 1977) in a territory mainly composed of densely populated areas also in mountainous and hilly regions. SCFs are clay-dominant terrains that, usually, give origin from very-slow to extremely-slow phenomena (Cruden and Varnes, 1996) with a long evolutionary history made up of multiple reactivations that makes difficult their identification, monitoring and susceptibility evaluation. The study has been carried out from point-wise (Bisaccia, Costa della Gaveta and Nerano cases) to wide areas (Palermo province case) where crops out SCFs as the Termini sandstones Formation (CARG, 2011), the Varicoloured Clays of Calaggio Formation (Ciaranfi et al., 1973), the Varicoloured Clays Unit (Mattioni et al., 2006) the Sicilide Unit (Vitale and Ciarcia, 2013 and references therein), the Numidian Flysch (Johansson et al., 1998) and the Corleone Calcarenites (Catalano R. et al., 2002). The aim of this thesis is to produce updated Landslide Inventory Maps and, whenever possible, Landslide Susceptibility Maps following a new approach during the landslide mapping and landslide monitoring stages. The Landslide Inventory Maps have taken into account the combination of geological, geomorphological, and stereoscopic surveys, as well as engineering geological investigations, namely conventional techniques. In addition innovative Advanced-Differential Interferometry Synthetic Aperture Radar (A-DInSAR) techniques have been used: the Coherent Pixels Technique – CPT (Mora et al., 2003; Blanco et al., 2008), the Intermittent Small BAseline Subset – ISBAS (Sowter et al., 2013) and the Ground-Based Synthetic Aperture Radar. Finally, the Weight of Evidence method (van Westen, 1993) has been chosen to generate the Landslide Susceptibility Maps only for the point-wise studies. In the case of Nerano (Province of Naples), the ISBAS analysis on ENVISAT images (for the period 2003-2010) has been carried out and compared with inclinometric and rainfall data. These have revealed several reactivations of a rotational slide + earth flow (Cruden and Varnes, 1996) that involves reworked clay olistostromes and limestone olistoliths inside the Termini sandstones Formation; even in recent years the landslide, despite many engineering works, has given evidence of a continuing activity. The results highlight a very slow movement in the detachment zone (<1 mm/yr), which assumes slightly higher values in the accumulation area (5 mm/yr). The Landslide Susceptibility Map confirms the high levels in the flow track and the accumulation area. In Bisaccia (Province of Avellino), a conglomeratic slab undergoes a Deep Seated Gravitational Slope Deformation (DSGSD; Pasuto and Soldati, 2013 and references therein) due to the bedrock consolidation, made of the Varicoloured Clays of Calaggio Formation. Here the CPT processing on ENVISAT images (covering the period between 2002 and 2010), displays a vertical displacement for the town center, suffering a progressively increasing velocity from the southern (4.2 mm/yr) to the northern (15.5 mm/yr) portion of the slab that localizes four different sectors. The pattern is confirmed from the building damage map. The landslides susceptibility reaches the highest values in the adjacent valleys and at the edges of each sector. Multiple datasets have been employed for the Costa della Gaveta case-study (Province of Potenza), these encompass: ENVISAT, TerraSAR-X and COSMO-SkyMed constellations together with Ground Based Synthetic Aperture Radar (GBSAR). The A-DInSAR data have been compared with stereoscopic analysis and the available rainfall and inclinometric data. The analysis allows for the identification of 16 landslides (complexes and earth flows; Cruden and Varnes, 1996) developed in the Varicoloured Clays Unit that show, according to all the existing instruments, velocities between 1.5 and 30 mm/yr. The western side of Costa della Gaveta slope is the portion which suffers the highest landslides susceptibility levels. In the Province of Palermo (northwestern Sicily) information deriving from A-DInSAR processing, specifically the ISBAS technique, have been focused on three subareas (Piana degli Albanesi, Marineo and Ventimiglia di Sicilia) for a total extension of 182 Km2 where standard A-DInSAR algorithms showed limitations due to the widespread presence of densely vegetated areas. The radar-detected landslides have been validated through field geomorphological mapping and stereoscopic analysis proving to be highly consistent especially with slow phenomena. The outcome has allowed to confirm 152 preexisting landslides, to detect 81 new events and to change 133 previously mapped landslides, modifying their typology, boundary and/or state of activity. The study demonstrates how a better knowledge of landslide development and their cause-effect mechanisms provided by new Earth Observation techniques is useful for Landslide Inventory and Susceptibility Maps. The research project has been carried out at the University of Naples "Federico II", including nine months (September 2013 – May 2014) spent in the United Kingdom, at the British Geological Survey under the supervision of Dr. Francesca Cigna and Dr. Jordan Colm and at the University of Nottingham (Department of Civil Engineering), under the supervision of Dr. Andrew Sowter where the ISBAS technique has been recently developed

Remote Sensing for Landslide Investigations: An Overview of Recent Achievements and Perspectives

Landslides represent major natural hazards, which cause every year significant loss of lives and damages to buildings, properties and lifelines. In the last decades, a significant increase in landslide frequency took place, in concomitance to climate change and the expansion of urbanized areas. Remote sensing techniques represent a powerful tool for landslide investigation: applications are traditionally divided into three main classes, although this subdivision has some limitations and borders are sometimes fuzzy. The first class comprehends techniques for landslide recognition, i.e., the mapping of past or active slope failures. The second regards landslide monitoring, which entails both ground deformation measurement and the analysis of any other changes along time (e.g., land use, vegetation cover). The third class groups methods for landslide hazard analysis and forecasting. The aim of this paper is to give an overview on the applications of remote-sensing techniques for the three categories of landslide investigations, focusing on the achievements of the last decade, being that previous studies have already been exhaustively reviewed in the existing literature. At the end of the paper, a new classification of remote-sensing techniques that may be pertinently adopted for investigating specific typologies of soil and rock slope failures is proposed

Characterizing slope instability kinematics by integrating multi-sensor satellite remote sensing observations

Over the past few decades, the occurrence and intensity of geological hazards, such as landslides, have substantially risen due to various factors, including global climate change, seismic events, rapid urbanization and other anthropogenic activities. Landslide disasters pose a significant risk in both urban and rural areas, resulting in fatalities, infrastructure damages, and economic losses. Nevertheless, conventional ground-based monitoring techniques are often costly, time-consuming, and require considerable resources. Moreover, some landslide incidents occur in remote or hazardous locations, making ground-based observation and field investigation challenging or even impossible. Fortunately, the advancements in spaceborne remote sensing technology have led to the availability of large-scale and high-quality imagery, which can be utilized for various landslide-related applications, including identification, monitoring, analysis, and prediction. This efficient and cost-effective technology allows for remote monitoring and assessment of landslide risks and can significantly contribute to disaster management and mitigation efforts. Consequently, spaceborne remote sensing techniques have become vital for geohazard management in many countries, benefiting society by providing reliable downstream services. However, substantial effort is required to ensure that such benefits are provided. For establishing long-term data archives and reliable analyses, it is essential to maintain consistent and continued use of multi-sensor spaceborne remote sensing techniques. This will enable a more thorough understanding of the physical mechanisms responsible for slope instabilities, leading to better decision-making and development of effective mitigation strategies. Ultimately, this can reduce the impact of landslide hazards on the general public. The present dissertation contributes to this effort from the following perspectives: 1. To obtain a comprehensive understanding of spaceborne remote sensing techniques for landslide monitoring, we integrated multi-sensor methods to monitor the entire life cycle of landslide dynamics. We aimed to comprehend the landslide evolution under complex cascading events by utilizing various spaceborne remote sensing techniques, e.g., the precursory deformation before catastrophic failure, co-failure procedures, and post-failure evolution of slope instability. 2. To address the discrepancies between spaceborne optical and radar imagery, we present a methodology that models four-dimensional (4D) post-failure landslide kinematics using a decaying mathematical model. This approach enables us to represent the stress relaxation for the landslide body dynamics after failure. By employing this methodology, we can overcome the weaknesses of the individual sensor in spaceborne optical and radar imaging. 3. We assessed the effectiveness of a newly designed small dihedral corner reflector for landslide monitoring. The reflector is compatible with both ascending and descending satellite orbits, while it is also suitable for applications with both high-resolution and medium-resolution satellite imagery. Furthermore, although its echoes are not as strong as those of conventional reflectors, the cost of the newly designed reflectors is reduced, with more manageable installation and maintenance. To overcome this limitation, we propose a specific selection strategy based on a probability model to identify the reflectors in satellite images

Tectonics and mud volcanism in the Northern Apennines foothills (Italy) and in the Greater Caucasus (Azerbaijan): a satellite interferometry (InSAR) analysis. Tettonica e vulcanismo di fango lungo il margine Pede-Appenninico emiliano e nel Gran Caucaso (Azerbaijan): un’analisi d’interferometria satellitare (InSAR).

ITALIANO Questo progetto di ricerca ha avuto l’obbiettivo di indagare sull’attività dei vulcani di fango presenti in contesti compressivi (catene a pieghe e thrust) e sulla tettonica delle strutture attive ad essi collegate, tramite la tecnica dell’interferometria radar satellitare. Le aree di studio sono due fronti orogenici: il margine Pede-appenninico dell’Appennino Settentrionale ed il margine sud-orientale del Grande Caucaso, entrambi caratterizzati dalla presenza di thrust attivi e del fenomeno del vulcanismo di fango. I vulcani di fango che caratterizzano il margine Emiliano-Romagnolo dell’Appennino Settentrionale, consistono generalmente in gryphons che possono raggiungere 3 o 4 m di altezza. Di dimensioni notevolmente maggiori sono invece i vulcani di fango presenti nel Gran Caucaso orientale (Azerbaijan), alcuni dei quali possono essere alti fino a 400 m, con diametro fino a 5 km, pertanto con dimensioni e caratteristiche morfologiche simili a quelle dei vulcani magmatici. I dati utilizzati per entrambe le zone di studio consistono in immagini radar Envisat, che sono state fornite dall'Agenzia Spaziale Europea (ESA) nel contesto di un progetto CAT1, creato appositamente per questo progetto di dottorato (CAT1 13866, dal titolo: Assessing the relationships between tectonics and mud volcanism by integrating DInSAR analysis and seismic data in active tectonic areas). La tecnica utilizzata in questo dottorato di ricerca è stata l’interferometria radar satellitare, che è stata impiegata attraverso due distinte metodologie: (1) l’interferometria differenziale (DInSAR) e (2) la Persistent Scatterers Interferometry (PSI). La scelta del tipo di metodologia è stata dettata da diversi fattori, in particolare (i) l’obiettivo specifico da raggiungere (studiare le deformazioni del suolo legate ai vulcani di fango oppure alle anticlinali sepolte), (ii) il numero di immagini Envisat disponibili nell’archivio dell’ESA e (iii) le caratteristiche fisiche delle due diverse aree di studio, (grado di urbanizzazione, uso del suolo, aridità) che incidono fortemente sulla risposta del dato radar. La tecnica DInSAR si è rivelata un ottimo strumento di analisi della deformazione superficiale presso i vulcani di fango, per quanto riguarda l’area di studio dell’Azerbaijan. Il periodo coperto dalle immagini Envisat utilizzate va da Ottobre 2003 a Novembre 2007. L’analisi di un ristretto set di interferogrammi selezionati in base ai migliori valori di coerenza, ha permesso di identificare importanti deformazioni superficiali in corrispondenza di 5 vulcani di fango, sia durante fasi prossime all’eruzione, sia durante fasi di normale attività di background. È stato possibile quindi osservare l’attività di questi oggetti da un punto di vista dinamico e di monitorare le deformazioni superficiali indotte da episodi di inflazione e deflazione. Tali pattern deformativi mostrano chiare analogie con l’evoluzione spazio-temporale delle deformazioni del suolo di vulcani magmatici descritti in letteratura, in relazione alle varie fasi di attività. Questo risultato rafforza pertanto l’idea che i vulcani di fango e quelli magmatici siano governati da processi simili, quali le variazioni di pressione e volume dei fluidi. La tecnica PSI ha prodotto risultati di grande interesse per quanto riguarda lo studio delle strutture tettoniche attive del settore più esterno dell’Appennino Settentrionale. Il periodo coperto dalle immagini utilizzate va da settembre 2004 a settembre 2010. I risultati permettono di individuare estese deformazioni del suolo in Pianura Padana, in particolare un (i) segnale di subsidenza (allontanamento rispetto al satellite lungo la linea di vista del satellite, LOS) nella zona a nord-est di Reggio Emilia ed un (ii) segnale di sollevamento (avvicinamento rispetto al satellite lungo la LOS) in alcune zone dell’area di studio tra Reggio Emilia e Piacenza. Purtroppo la bassa risoluzione delle immagini Envisat non ha permesso l’analisi dei piccoli apparati dei vulcani di fango presenti sul margine Pede-appenninico. I dati GPS presenti nell’area di studio sono stati confrontati con i risultati della tecnica PSI. Per permetterne il confronto con le misurazioni da satellite, i dati GPS sono stati proietatti lungo la LOS (line of sight) del satellite. La subsidenza in Pianura Padana è un fenomeno molto ben conosciuto, in quanto si tratta in primo luogo di subsidenza indotta da attività antropiche, quali l’estrazione di acqua. Le aree in sollevamento, che sono l’oggetto di primario interesse di questo lavoro, mostrano deformazioni che vanno da 1 fino a picchi di 2,8 mm/anno. È interessante notare che quasi tutte le aree in sollevamento si trovano in corrispondenza di thrust attivi delle pieghe Emiliane e Ferraresi e sono caratterizzate dalla presenza di sismicità soprattutto storica. Data questa corrispondenza spaziale, avanziamo l’ipotesi (documentata dall’analisi delle serie temporali e dal confronto con le sezioni sismiche con i profili di velocità di deformazione) che esista una correlazione fra l’attività delle anticlinali sepolte sotto la Pianura Padana ed il sollevamento delle zone soprastanti queste strutture e che quest’ultime si sollevino con un movimento di creep asismico. Le faglie inverse attivate in occasione della sequenza sismica del Maggio 2012 (Finale Emilia e Mirandola) potrebbero aver avuto una simile evoluzione pre-sismica, e cioè sollevamento del suolo e scarsa sismicità. Tuttavia il fatto che alcune delle anticlinali di crescita studiate siano in sollevamento non implica che si arrivi necessariamente ad un sisma, anche se i risultati di questo lavoro dovrebbero essere presi in considerazione nella valutazione del rischio sismico dell’area di studio. Per concludere, le tecniche di interferometria satellite hanno dimostrato di essere efficaci per studiare diversi tipi di processi geologici attivi e costituiscono un mezzo molto vantaggioso per misurare i tassi di deformazione del suolo e quindi per valutare i rischi geologici. INGLESE Satellite radar interferometry provides some unique capabilities for assessing geological rates of deformation and therefore for studying active geological processes. This Ph.D. thesis employs the interferometric techniques for studying the activity of mud volcanoes and the ongoing tectonics of the related compressive structures. Mud volcanoes indeed usually develop at convergent plate margins, and occur in fold-and-thrust belts. The study areas are two orogenic fronts, namely: the Northern Apennines margin (Emilia-Romagna region; Northern Italy) and the southeastern Great Caucasus margin (Azerbaijan), both characterized by the presence of active thrust folds and mud volcanism. The latter is typically linked to hydrocarbon traps and leads to the extrusion of subsurface mud breccias that build up a variety of conical edifices. Interferometry has been applied, using Envisat images, through both (1) the Differential Satellite based Synthetic Aperture Radar Interferometry (DInSAR) approach for studying the ground deformations related to mud volcano activity, and (2) the Persistent Scatterers Interferometry (PSI) in order to investigate the ongoing tectonics along fold-and-thrust belt margins. The first goal has been developed for the Azerbaijan mud volcanoes. The results are encouraging, since it was possible to observe the mud volcanoes activity from a dynamic point of view, and to infer the processes that drive the deformation. The detected ground deformation events at mud volcanoes edifices are in general due to the fluid pressure and volume variations, and they have been observed both (i) in connection with main eruptive events, in the form of pre-eruptive uplift (~20 cm in about two years of cumulative uplift at the Ayaz-Akhtarma mud volcano), and (ii) in the form of short-lived deformation pulses that interrupt a period of quiescence. Important similarities with the deformation pattern of magmatic volcanoes have been proposed. The second goal has been carried out for the outermost sector of the Northern Apennines including the Po Plain between Piacenza and Reggio Emilia. This study attempts to correlate the superficial deformation signals measured by radar satellite-based sensor with the known geological features. The PSs velocity pattern shows some ground uplift above active thrust-related anticlines (with mean velocities ranging from 1 to 2.8 mm/yr) of the Emilia and Ferrara folds, and part of the Pede-Apennine margin. On this basis, a correlation between the observed ground uplift and the ongoing activity of the tectonic structures is proposed. The results of the current analysis would thus be taken into account when evaluating the seismic hazard of the study region