DInSAR techniques for studying the October 23, 2011, Van earthquake (Turkey), and its relationship with neighboring structures

In October 2011 a strong earthquake hit the Van province, Eastern Turkey. Few days later (November 9th) an aftershock occurred few km southward. Finally in November 1976 another mainshock took place north of Van along the Caldiran fault. We have investigated the possible relations between 2011 mainshock and aftershock and the link with the 1976 earthquake. In order to complete the work SAR interferometry has been applied to measure surface displacements, while the fault geometries of the mainshock have been retrieved by a novel Neural Network approach. Moreover the CFF has been calculated to evaluate the role of 1976 earthquake in promoting the 2011 mainshock and, later on, the role of this latter respect to the aftershock in November 9th, 201

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

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

Improved modeling of segmented earthquake rupture informed by enhanced signal analysis of seismic and geodetic observations

Earthquake source modeling has emerged from the need to be able to describe and quantifythe mechanism and physical properties of earthquakes. Investigations of earthquake ruptureand fault geometry requires the testing of a large number of such potential sets of earthquakesources models. Earthquakes often rupture across more than one fault segment. If such rupturesegmentation occurs on a significant scale, a simple model may not represent the rupture processwell. This thesis focuses on the data-driven inclusion of earthquake rupture segmentation intoearthquake source modeling. The developed tools and the modeling are based on the jointuse of seismological waveform far-field and geodetic Interferometric Synthetic Aperture Radarnear-field surface displacement maps to characterise earthquake sources robustly with rigorousconsideration of data and modeling errors.A strategy based on information theory is developed to determine the appropriate modelcomplexity to represent the available observations in a data-driven way. This is done inconsideration of the uncertainties in the determined source mechanisms by investigating theinferences of the full Bayesian model ensemble. Application on the datasets of four earthquakesindicated that the inferred source parameters are systematically biased by the choice of modelcomplexity. This might have effects on follow-up analyses, e. g. regional stress field inversionsand seismic hazard assessments.Further, two methods were developed to provide data-driven model-independent constraints toinform a kinematic earthquake source optimization about earthquake source parameter priorestimates. The first method is a time-domain multi-array backprojection of teleseismic datawith empirical traveltime corrections to infer the spatio-temporal evolution of the rupture. Thisenables detection of potential rupture segmentation based on the occurrence of coherent high-frequency sources during the rupture process. The second developed method uses image analysismethods on satellite radar measured surface displacement maps to infer modeling constraints onrupture characteristics (e.g. strike and length) and the number of potential segments. These twomethods provide model-independent constraints on fault location, dimension, orientation andrupture timing. The inferred source parameter constraints are used to constrain an inversion forthe source mechanism of the 2016 Muji Mw 6.6 earthquake, a segmented and bilateral strike-slipearthquake.As a case study to further investigate a depth-segmented fault system and occurrence of co-seismic rupture segmentation in such a system the 2008-2009 Qaidam sequence with co-seismicand post-seismic displacements is investigated. The Qaidam 2008-2009 earthquake sequence innortheast Tibet involved two reverse-thrust earthquakes and a postseismic signal of the 2008earthquake. The 2008 Qaidam earthquake is modeled as a deep shallow dipping earthquakewith no indication of rupture segmentation. The 2009 Qaidam earthquake is modeled on threedistinct south-dipping high-angle thrusts, with a bilateral and segmented rupture process. Agood agreement between co-seismic surface displacement measurements and coherent seismicenergy emission in the backprojection results is determined.Finally, a combined framework is proposed which applies all the developed methods and tools inan informed parallel modeling of several earthquake source model complexities. This frameworkallows for improved routine determination of earthquake source modeling under considerationof rupture segmentation. This thesis provides overall an improvement for earthquake sourceanalyses and the development of modeling standards for robust determination of second-orderearthquake source parameters

Land Surface Monitoring Based on Satellite Imagery

This book focuses attention on significant novel approaches developed to monitor land surface by exploiting satellite data in the infrared and visible ranges. Unlike in situ measurements, satellite data provide global coverage and higher temporal resolution, with very accurate retrievals of land parameters. This is fundamental in the study of climate change and global warming. The authors offer an overview of different methodologies to retrieve land surface parameters— evapotranspiration, emissivity contrast and water deficit indices, land subsidence, leaf area index, vegetation height, and crop coefficient—all of which play a significant role in the study of land cover, land use, monitoring of vegetation and soil water stress, as well as early warning and detection of forest fires and drought

ALOS-2/PALSAR-2 Calibration, Validation, Science and Applications

Twelve edited original papers on the latest and state-of-art results of topics ranging from calibration, validation, and science to a wide range of applications using ALOS-2/PALSAR-2. We hope you will find them useful for your future research

From Regional Landslide Detection to Site-Specific Slope Deformation Monitoring and Modelling Based on Active Remote Sensors

Landslide processes can have direct and indirect consequences affecting human lives and activities. In order to improve landslide risk management procedures, this PhD thesis aims to investigate capabilities of active LiDAR and RaDAR sensors for landslides detection and characterization at regional scales, spatial risk assessment over large areas and slope instabilities monitoring and modelling at site-specific scales. At regional scales, we first demonstrated recent boat-based mobile LiDAR capabilities to model topography of the Normand coastal cliffs. By comparing annual acquisitions, we validated as well our approach to detect surface changes and thus map rock collapses, landslides and toe erosions affecting the shoreline at a county scale. Then, we applied a spaceborne InSAR approach to detect large slope instabilities in Argentina. Based on both phase and amplitude RaDAR signals, we extracted decisive information to detect, characterize and monitor two unknown extremely slow landslides, and to quantify water level variations of an involved close dam reservoir. Finally, advanced investigations on fragmental rockfall risk assessment were conducted along roads of the Val de Bagnes, by improving approaches of the Slope Angle Distribution and the FlowR software. Therefore, both rock-mass-failure susceptibilities and relative frequencies of block propagations were assessed and rockfall hazard and risk maps could be established at the valley scale. At slope-specific scales, in the Swiss Alps, we first integrated ground-based InSAR and terrestrial LiDAR acquisitions to map, monitor and model the Perraire rock slope deformation. By interpreting both methods individually and originally integrated as well, we therefore delimited the rockslide borders, computed volumes and highlighted non-uniform translational displacements along a wedge failure surface. Finally, we studied specific requirements and practical issues experimented on early warning systems of some of the most studied landslides worldwide. As a result, we highlighted valuable key recommendations to design new reliable systems; in addition, we also underlined conceptual issues that must be solved to improve current procedures. To sum up, the diversity of experimented situations brought an extensive experience that revealed the potential and limitations of both methods and highlighted as well the necessity of their complementary and integrated uses