A review of geothermal mapping techniques using remotely sensed data

Exploiting geothermal (GT) resources requires first and foremost locating suitable areas for its development. Remote sensing offers a synoptic capability of covering large areas in real time and can cost effectively explore prospective geothermal sites not easily detectable using conventional survey methods, thus can aid in the prefeasibility stages of geothermal exploration. In this paper, we evaluate the techniques and approaches used in literature for the detection of prospective geothermal sites. Observations have indicated that, while thermal temperature anomalies detection have been applicable in areas of magmatic episodes and volcanic activity, poor resolution especially from space borne data is still a challenge. Consequently, thermal anomalies have been detected with some degree of success using airborne data, however, this is mostly in locations of known surface manifestations such as hot springs and fumaroles. The indirect identification of indicator minerals related to geothermal systems have been applied using multispectral and hyperspectral data in many studies. However, the effectiveness of the techniques relies on the sophistication and innovative digital image processing methods employed to sieve out relevant spectral information. The use of algorithms to estimate land surface temperature and heat fluxes are also applied to aid thermal anomaly detection, nevertheless, remote sensing techniques are still complementary to geologic, geophysical and geochemical survey methods. While not the first of its kind, this review is aimed at identifying new developments, with a focus on the trends and limitations intrinsic to the techniques and a look at current gaps and prospects for the future.Keywords: Geothermal, remote sensing, thermal anomalies, indicator minerals, multispectral, hyperspectra

Urban morphology analysis by remote sensing and gis technique, case study: Georgetown, Penang

This paper was analysed the potential of applications of satellite remote sensing to urban planning research in urban morphology. Urban morphology is the study of the form of human settlements and the process of their formation and transformation. It is an approach in designing urban form that considers both physical and spatial components of the urban structure. The study conducted in Georgetown, Penang purposely main to identify the evolution of urban morphology and the land use expansion. In addition, Penang is well known for its heritage character, especially in the city of Georgetown with more than 200 years of urban history. Four series of temporal satellite SPOT 5 J on year 2004, 2007, 2009 and 2014 have been used in detecting an expansion of land use development aided by ERDAS IMAGINE 2014. Three types of land uses have been classified namely build-up areas, un-built and water bodies show a good accuracy with achieved above 85%. The result shows the built-up area significantly increased due to the rapid development in urban areas. Simultaneously, this study provides an understanding and strengthening a relation between urban planning and remote sensing applications in creating sustainable and resilience of the city and future societies as well

A Hybrid Clustering-Fusion Methodology for Land Subsidence Estimation

A hybrid clustering-fusion methodology is developed in this study that employs Genetic Algorithm (GA) optimization method, k-means method, and several soft computing (SC) models to better estimate land subsidence. Estimation of land subsidence is important in planning and management of groundwater resources to prevent associated catastrophic damages. Methods such as the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) can be used to estimate the subsidence rate, but PS-InSAR does not offer the required efficiency and accuracy in noisy pixels (obtained from remote sensing). Alternatively, a fusion-based methodology can be used to estimate subsidence rate, which offers a superior accuracy as opposed to the traditionally used methods. In the proposed methodology, five SC methods are employed with hydrogeological forcing of frequency and thickness of fine-grained sediments, groundwater depth, water level decline, transmissivity and storage coefficient, and output of land subsidence rate. Results of individual SC models are then fused to render more accurate land subsidence rate in noisy pixels, for which PS-InSAR cannot be effective. We first extract 14,392 different input-output patterns from PS-InSAR technique for our study area in Tehran province, Iran. Then, k-means method is used to divide the study area to homogenous zones with similar features. The five SC models include Adaptive Neuro Fuzzy Inference System (ANFIS), Support Vector Regression (SVR), Multi-Layer Perceptron (MLP) neural network and two optimized models, namely, Radial Basis Function (RBF) and Generalized Regression Neural Network (GRNN). To fuse individual SC models, three methods including Genetic Algorithm (GA), K-Nearest Neighbors (KNN) and Ordered Weighted Average (OWA) based on ORNESS method and ORLIKE method, are developed and evaluated. Results show that the fusion-based method is significantly superior to each of the employed individual methods in predicting land subsidence rate

Application of Small Baseline Subset (SBAS)-INSAR Technique to Study Surface Deformation Due to The Grindulu Fault Activities using Sentinel-1 Data

Numerous variables contribute to the deformation; for instance, local thrust movements, human-made activities, and seismic activity along the Grindulu Fault. The Meteorological, Climatological, and Geophysical Agency of Indonesia (BMKG) reported seismic activities in Pacitan were delivered following November 7, 2019, earthquake, which could indicate the existence of the Grindulu Fault. The location of Grindulu Fault is in the Pacitan Regency on the Southern Coast of Java which directly faces the South Java Subduction zone. In this research, we identify fault activities through the detection around the Grindulu Fault to reduce the disaster risk in Pacitan Regency. Twenty-three ascending Sentinel-1B images and Small Baseline Subset InSAR technique were used to monitor ground deformation in Pacitan Regency between 2019 and 2021. SBAS-InSAR is one of the approaches for analysis techniques that can provide techniques continuous measurements of the ground deformation; it produces mean LOS velocity throughout the Line of Sight (LOS) around the Grindulu Fault segment. The processing was carried out using the GMTSAR software and compared the result using SBAS generated by open-source LiCSBAS of open-source SAR processing result showed deformation in the form of land subsidence in almost all of the Pacitan, with the mean velocity ranging from –2.1 to -43.1 mm/yr. The cause of deformation is the same thing, the existing Grindulu fault. The SBAS result confirmed with geological and geomorphological conditions such Triangular facets, braided rivers, and depression zone near Grindulu fault. Furthermore, the comparison results with the mean LOS velocity from LiCSBAS show that the area around Grindulu Fault also experiences land subsidence. Even though the RMSE value obtained is 13.7 mm/yr, it is demonstrating that the SBASInSAR velocity generated by GMTSAR processing not enough corresponds to the LiCSBAS. ======================================================================================================================================== Banyak variabel berkontribusi pada deformasi; misalnya, gerakan tektonik lokal, atau bahkan aktivitas manusia maupun seismik di sepanjang Sesar Grindulu. Badan Meteorologi, Klimatologi, dan Geofisika Indonesia (BMKG) melaporkan aktivitas seismik di Pacitan terdeteksi yakni berupa gempabumi pada 7 November 2019, yang dapat menjadi indikasi keberadaan Sesar Grindulu. Letak Sesar Grindulu berada di Kabupaten Pacitan dekat dengan Pesisir Selatan Jawa dan berhadapan langsung dengan zona Subduksi Selatan Jawa. Pada penelitian dilakukan identifikasi aktivitas sesar melalui deformasi yang terjadi di sekitar Sesar Grindulu, sehingga dapat mengurangi risiko bencana di Kabupaten Pacitan. Dua puluh tiga citra ascending Sentinel-1B dan teknik Small Baseline Subset InSAR digunakan untuk memantau deformasi tanah di Kabupaten Pacitan antara tahun 2019 dan 2021. SBAS-InSAR adalah salah satu pendekatan untuk memberikan pengukuran deformasi tanah secara kontinu dalam bentuk rata-rata kecepatan deformasi disepanjang Line of Sight (LOS). Pemrosesan dilakukan dengan menggunakan perangkat lunak GMTSAR yang kemudian dibandingkan dengan menggunakan SBAS yang dihasilkan oleh perangkat lunak open source, LiCSBAS. Hasil pengolahan GMTSAR menunjukkan deformasi berupa penurunan muka tanah di hampir seluruh wilayah Pacitan, dengan kecepatan rata-rata berkisar antara –2,1 hingga -43,1 mm/tahun. Penyebab deformasi adalah hal yang sama, yaitu keberadaan sesar Grindulu. Hasil SBAS terkonfirmasi dengan kondisi geologi dan geomorfologi berupa triangular facets, bentuk aliran sungai, dan zona depresi di dekat sesar Grindulu. Selain itu, hasil perbandingan nilai rata-rata kecepatan LOS LiCSBAS menunjukkan bahwa di sekitar Sesar Grindulu juga mengalami penurunan muka tanah. Meskipun nilai RMSE yang diperoleh adalah 13,7 mm/tahun, hal ini menunjukkan bahwa nilai SBASInSAR yang dihasilkan oleh pengolahan GMTSAR belum cukup sesuai dengan hasil LiCSBAS

Spatial Analysis of Jiroft Plain Subsidence Using the Coherence Pixel Technique (CPT)

AbstractThe phenomenon of land subsidence is one of the most important environmental hazards that have affected many plains of the country today. Jiroft Plain located in Kerman Province is also one of the areas where subsidence effects are evident. In this research, besides analyzing the spatial subsidence of Jiroft Plain and determining the extent and trend of its spread over a period of time, the effective factors in this phenomenon were investigated. For this purpose, the Sentinel-1 radar images related to the years of 2014-2022 were used. The Coherence Pixel Technique (CPT) was utilized to map the affected areas and determine the subsidence rate. The results of this method showed that the subsidence rate in Jiroft Plain had increased from 11 cm in 2014 to 13 cm in 2022. In addition, its area had increased during this period and the expansion trend had moved towards the northern areas of the plain. To analyze the causative factors of this phenomenon, in addition to studying the changes in the groundwater level of the plain and its relationship with subsidence, the roles of faults and soil thickness in creating or intensifying this phenomenon were investigated. The results showed that in addition to the uncontrolled abstraction from the aquifer, the subsidence of Jiroft Plain was affected by Sabzevaran Fault, while subsidence intensity was higher in the areas with higher soil thickness.Keywords: subsidence, groundwater, fault, spatial relationship, Jiroft Plain IntroductionThe phenomenon of subsidence is one of the growing and fundamental problems in most human societies, which often occurs as a result of human activities. Improper use of water in agricultural and industrial sectors due to the increasing population growth has led to adverse quantitative and qualitative effects on water resources. Understanding the spatial extent and measuring the amount of subsidence as accurately as possible can be considered as the first step in studying this phenomenon. Therefore, by recognizing the spatial characteristics and temporal behavior of this phenomenon, it is possible to present and develop a regional model of it as well as practical and basic solutions to reduce the damage associated with it and prevent its future trends. The use of radar interferometry method in recent years as an efficient tool for monitoring displacements caused by various phenomena, such as volcanoes, subsidence, earthquakes, and landslides, etc., has been considered by earth scientists. The advantages of this method compared to the previous one include the possibility of calculating displacements with centimeter-level accuracy, providing continuous and extensive spatial coverage, and having the ability to operate it in any weather conditions. So far, various studies have qualitatively identified the relationship between groundwater level declines and occurrence of subsidence. However, few studies have tested this relationship quantitatively. Jiroft Plain has been facing a serious drought crisis and declining groundwater levels in recent years. In fact, changes in the agricultural pattern, reduced rainfall, and occurrence of continuous droughts have led to unplanned and unprincipled use of groundwater resources and decline of groundwater levels in the catchment area of Jiroft Plain and have provided conditions for the occurrence and expansion of land subsidence. Therefore, subsidence monitoring has been proposed as an efficient method for identifying and displaying the regional situations in terms of the risk of land subsidence by planners and managers and made it possible to plan and implement appropriate prevention programs. Therefore, the purpose of this paper was spatial analysis of Jiroft Plain subsidence and evaluation of the effects of uncontrolled groundwater abstraction on land subsidence and fault development. To this end, 73 Sentinel-1 images related to the period of 2014-2021 were processed by using the CPT technique. The darkest areas were related to agricultural areas, which had the least amounts of coherence since their vegetations had not remained constant over time and caused a temporal correlation in the interfering phase. MethodologyThe first step in the CPT processing was production of differential interferometers. Initially, the images were referenced in pairs and the interferometers were selected from the items that had spatial and temporal baselines of less than 100 and 365 m, respectively. Based on this, 72 mapping overlays were generated. Along with the various interferences, the related coherence maps were generated. Coherence is a good estimator of phase quality and is used in the pixel selection phase. Coherence values range from 0 that shows a completely uncorrelated phase or pure noise to 1 that indicates a coherent or noise-free phase. In the second step, differential interferometers were processed to obtain the deformation time series, which included linear and nonlinear components and DEM error. Not all image pixels are suitable for processing due to lacking correlation. Among the various pixel selection criteria, a coherence-based criterion was used. Therefore, all the pixels that had a mean coherence value of less than 0.6 were discarded. Figure 3 shows the coherence map created by the CPT for Jiroft Plain where the brightest areas showed the most coherent areas, which corresponded to barren lands, mountainous lands and highlands, and residential areas because they showed very little change over time. DiscussionFigure 4 shows the magnitude of the shifts that occurred along the satellite's line of sight as a result of Sentinel-1 data processing from April 12, 2014 to September 21, 2021. The total number of pixels calculated from the Sentinel-1 data set by the CPT technique reached 2571. The calculations revealed a high deformation rate with a maximum speed of up to -13 cm per year for satellite visibility in the central and southern parts of Jiroft Plain from 2014 to 2021. The positive values indicated that the surface was rising. Most of these values were located in the mountains around the plain. Motion may be related to tectonic factors and the isostatic process. In contrast, the negative values indicated subsidence, which was mainly concentrated in the central and southern parts of the plain. As can be seen in Figure 4, the displacements in the direction of satellite view of the points varied from +3 to -13 mm. In addition, the results showed the increasing trend of subsidence over time in Jiroft Plain. From 2014 to 2022, the area affected by subsidence had increased from 530 km2 in 2014 to 580 km2 in 2022, showing an expansion from the southern to the northern areas of the plain. In addition to the extent of the subsidence rate, it had increased from 11 cm in 2014 to 13 cm in 2022. ConclusionIn this study, the subsidence phenomenon of Jiroft Plain was investigated and its relationship with various factors was analyzed. The displacements that had occurred and were then obtained from the CPT technique indicated that the study area had undergone progressive subsidence. The subsidence rate in the southern and southeastern parts of the plain had increased from 11 ear to 13 cm per year over an 8-year period. In addition, during this period, the area affected by this phenomenon had increased from 530 to 580 km2 and had been drawn to the northern parts of the plain over time. Investigation of groundwater level changes in Jiroft Plain and its compliance with the subsidence areas showed that improper abstraction from the aquifer had been an important and key factor in creating this phenomenon. In addition, it is worth noting that the areas with the highest subsidence rate corresponded to the areas with the highest soil thickness. Thus, their impacts on the subsidence were investigated due to the enclosure of Jiroft Plain by faults. The results of this study showed that Sabzevaran Fault had controlled subsidence and affected this phenomenon. Finally, the subsidence of Jiroft Plain could be considered as a result of two factors, one was the uncontrolled abstraction of groundwater and the other one was the activity of faults, which could affect each other. This issue had intensified the subsidence phenomenon

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

Volcanic deformation and degassing:the role of volatile exsolution and magma compressibility

Integrating multi-parameter observations of volcanic processes is crucial for volcano monitoring. Qualitative models demonstrate that combining observations of volcanic deformation, gas emissions, and other parameters enhances the detection of volcanic unrest and provide insights into the magma plumbing system. Despite the progress made in this field, quantitative models that link these observations are still lacking. Thermodynamic models have been used to constrain the characteristics of magma properties and its plumbing system. In this thesis, I develop models based on melt inclusion data and thermodynamics to reconstruct magma properties such as compressibility, and investigate how magmatic volatile content and magma storage conditions influence observations of volcanic deformation and SO2 degassing.By comparing mafic systems in arc and ocean island settings, I provide evidence for the lack of deformation observed during water-rich arc eruptions. In contrast, despite having low magmatic volatile content, ocean island eruptions have high SO2 emissions due to their high diffusivity, which results in co-eruptive degassing. By comparing model predictions and observations, I show that all magmatic systems experience a certain degree of outgassing prior to an eruption, consistent with current conceptual models of transcrustal magmatic systems. Additionally, integrating time series of deformation, degassing, and extrusion flux can reveal the evolution of magma properties. Using this framework, I provide evidence for the increase in bulk magma compressibility following the removal of the degassed magma during the 2004 eruption of Mount St. Helens. This study contributes to the better understanding of the effects of magmatic volatile content and pre-eruptive gas segregation on the physicochemical properties of magma, and provides a framework for modelling magma properties that can be applied to global volcano monitoring.</div