Ground Deformation Monitoring Research Articles

Multiple-input multiple-output radar, ground-based MIMO SAR for ground deformation monitoring

ABSTRACT This study focuses on investigating the capabilities of a Multiple-input multiple-output RADAR. A Radar interferometer, based on an electronically scanned array in MIMO configuration (MIMO‐SAR), has been assessed for operational use in monitoring phenomena of geological interest, such as landslides unstable slopes. The system applies the very well‐known and proven Ground-Based Interferometric technique. It guarantees a very short refreshing time compared to traditional systems based on the mechanical movement of the radar transceiver on a rail or the mechanical steering of a real antenna. The system can monitor several phenomena having deformation rates too high to be correctly retrieved by traditional systems currently in use. Implementing a prototype termed MELISSA allowed the testing technique’s performances in two real case studies: a landslide and an unstable volcanic flank. The experimental results were compared with LISA, a well-known Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) interferometer. MELISSA allows for obtaining an excellent accuracy, better than 0.01 mm. The range and angular resolution are on the same order of magnitude as those obtained through LISA. However, the refreshing rate obtained from MELISSA, 0.01 s, guarantees a strong coherence even in challenging environmental scenarios as a flank of an active volcano.

LZER0: A Cost-Effective Multi-Purpose GNSS Platform.

Recent advances in Global Navigation Satellite System (GNSS) technology have made low-cost sensors available to the mass market, opening up new opportunities for real-time ground deformation and structure monitoring. In this paper, we present a new product developed in this framework by the National Institute of Oceanography and Applied Geophysics-OGS in collaboration with a private company (SoluTOP SAS): a cost-effective, multi-purpose GNSS platform called LZER0, suitable not only for surveying measurements, but also for monitoring tasks. The LZER0 platform is a complete system that includes the GNSS equipment (M8T single-frequency model produced by u-blox) and the web portal where the results are displayed. The GNSS data are processed using the RTKLIB software package, and the processed results are made available to the end user. The relative positioning mode was adopted both with real-time and post-processing RTKLIB engines. We present three applications of LZER0-cadastral, monitoring, and automotive-which demonstrate that it is a flexible, multi-purpose platform that is easy to use in terms of both hardware and software, and can be easily deployed to perform various tasks in the research, educational, or professional sectors.

Exploring the Kinematic Structure of Mount Etna Volcano (Sicily, Italy) by Deformation Analysis and Gravity Gradient Tensors

Ground deformation monitoring of active volcanoes is used routinely to determine phases of vol‐ cano unrest and can provide insights in the evolving plumbing system of a volcano and the influence local tectonics structures have on the volcano tectonic evolution of the volcanic edifice. Volcanic deformation analysis can be performed using velocity and direction measurements of the ground surface using Global Navigation Satellite System (GNSS). In this study, we perform two‐dimen‐ sional deformation analyses of pre‐ and post‐eruptive phases with the scope of determining the strain before and after an eruptive phase at Mt. Etna Volcano (southern Italy) during 2004‐2006. In order to do so, we analyse the GNSS displacement data from Mt. Etna between 2004‐2005 and 2005‐2006 using the dedicated SSPX software. The extention, dilation and rotation maps of the study area were determined. The contraction and volumetric decrease concomitant the 2004‐2005 effusive eruptive period and extension and volumetric increase for the 2005‐2006 data series were observed. The deformation on the northeast part of Mt. Etna Volcano, which showed different characteristics with respect to its surroundings, was thought to be conditioned by the dynamic of the Pernicana fault system. Additionally, Complete Spherical Bouguer (CSB) gravity anomaly and the gravity gradient tensors were calculated giving insight on the subsurface structures of Mt. Etna Volcano and its surroundings.

Ground deformation assessment of the Albertine graben using inSAR

Information on deformation of the land surface is vital for planning of infrastructure especially in areas such as the Albertine graben with substantial amounts of oil discoveries. Traditionally, global positioning systems, precise leveling and geotechnical techniques have been used for assessing and monitoring ground deformations. While these techniques provide accurate information, they are point based, expensive, time consuming and labour intensive over large area monitoring. This study explored an interferometric synthetic aperture radar (InSAR) approach for mapping deformation over Buliisa oil discovery area located in the Western arm of the East African rift valley. The method was implemented by measuring the phase differences of ALOS PALSAR data acquired between 2007 and 2011. Deformation estimates varied between -0.45m to +0.34m while the mean displacements varied from –0.10m to 0.089m. High ground deformation was detected in the Southern, North Eastern and North Western parts contributed by agricultural activity and drilling pad constructions. Generally, analysis of ALOS PALSAR data using InSAR approach provides a viable option for assessing land surface deformation in Buliisa oil exploration area.

Patch-Like Reduction (PLR): A SAR Offset Tracking amplitude filter for deformation monitoring

As complementary to Synthetic Aperture Radar (SAR) Differential Interferometry (DInSAR), SAR Offset Tracking (OT) is an efficient tool for large ground deformation monitoring in situations when DInSAR cannot work. However, SAR images are affected by speckle noise and some strong point-like scatters which can cause what is known as Patch Like (PL), a kind of errors that can be seen as homogeneous patches of almost constant deformation in the results. These errors are clearly visible in the results as non-consistent deformations along time, but they are difficult to detect with the traditional metrics that evaluate the cross-correlation results, like the Signal to Noise Ratio (SNR). This paper addresses this problem and proposes a simple amplitude filter to reduce PL named as Patch Like Reduction (PLR). The main idea is to find a sensor and scene independent threshold to remove the high amplitude pixels prone to cause PL. Five different SAR data sets and in-field GPS measurements are used to determine the optimal threshold and evaluate the performance of the proposed method. The results show that PL effects can be reduced with the proposed amplitude filter. The processing parameters of the improved OT processing chain are optimized as well to preserve the results resolution as much as possible. • The causes of Patch Like errors in Offset Tracking results have been investigated. • An amplitude filter (PLR) has been proposed to reduce PLs. • The filter threshold is automatically defined from images amplitude distributions. • The filter improves OT results by reducing the changes of PL appearance. • Template sizes and tapering windows have been optimized in terms of resolution.

A Strategy for Variable-Scale InSAR Deformation Monitoring in a Wide Area: A Case Study in the Turpan–Hami Basin, China

In recent years, increasing available synthetic aperture radar (SAR) satellite data and gradually developing interferometric SAR (InSAR) technology have provided the possibility for wide-scale ground-deformation monitoring using InSAR. Traditionally, the InSAR data are processed by the existing time-series InSAR (TS–InSAR) technology, which has inefficient calculation and redundant results. In this study, we propose a wide-area InSAR variable-scale deformation detection strategy (hereafter referred to as the WAVS–InSAR strategy). The strategy combines stacking technology for fast ground-deformation rate calculation and advanced TS–InSAR technology for obtaining fine deformation time series. It adopts an adaptive recognition algorithm to identify the spatial distribution and area of deformation regions (regions of interest, ROI) in the wide study area and uses a novel wide-area deformation product organization structure to generate variable-scale deformation products. The Turpan–Hami basin in western China is selected as the wide study area (277,000 km2) to verify the proposed WAVS–InSAR strategy. The results are as follows: (1) There are 32 deformation regions with an area of ≥1 km2 and a deformation magnitude of greater than ±2 cm/year in the Turpan–Hami basin. The deformation area accounts for 2.4‰ of the total monitoring area. (2) A large area of ground subsidence has occurred in the farmland areas of the ROI, which is caused by groundwater overexploitation. The popularization and application of facility agriculture in the ROI have increased the demand for irrigation water. Due to the influence of the tectonic fault, the water supply of the ROI is mainly dependent on groundwater. Huge water demand has led to a continuous net deficit in aquifers, leading to land subsidence. The WAVS–InSAR strategy will be helpful for InSAR deformation monitoring at a national/regional scale and promoting the engineering application of InSAR technology.

A hybrid method for MT-InSAR phase unwrapping for deformation monitoring in urban areas

• A hybrid method is proposed to enhance the phase unwrapping of MT-InSAR in urban. • Consideration of the impact of building height and spatial network structure. • Improvements in phase unwrapping allow for better geocoding of coherent points. The accuracy of phase unwrapping in multi-temporal interferometric synthetic aperture radar (MT-InSAR) technology affect closely on the accuracy of ground deformation monitoring. In the urban area, urban infrastructures such as high-rise buildings present additional challenges to phase unwrapping due to the sudden elevation changes. The failure rate of phase unwrapping is often much higher in such areas, bringing more biases to the estimated deformation and height values. We propose a new method for MT-InSAR phase unwrapping especially for deformation monitoring in urban areas. The method isolates the propagation path of information by considering the building height information of a study area. Two quality controllers are also developed to refine the arc observation network structure for network adjustment and to correct the phase unwrapping errors. The proposed method is tested using both simulated and real datasets. The results show that the building height and the geolocation of the coherence points were estimated much more accurately, demonstrating the effectiveness of the proposed method in monitoring deformation of urban area.

High resolution C-band SAR backscatter response to peatland water table depth and soil moisture: a laboratory experiment

ABSTRACT Carbon storage and active carbon sequestration within peatlands strongly depend on water table depth and soil moisture availability. With increasing efforts to protect and restore peatland ecosystems, the assessment of their hydrological condition is highly necessary but remains challenging. Synthetic aperture radar (SAR) satellite observations likely offer an efficient way to obtain regular information with complete spatial coverage over northern peatlands. Studies have indicated that both radar backscatter amplitude and phase are sensitive to peatland condition. Very recently, Differential Interferometric Synthetic Aperture Radar (DInSAR) has been reported as being capable of monitoring ground deformation patterns at the millimetre scale, which are a response to peatland hydrological condition. To further investigate the promise of SAR for peatland monitoring, a laboratory-based polarimetric C-band SAR system was used to acquire the dynamic radar behaviour of a 4 m (l) ×1 m (w) × 0.25 m (d) reconstructed peatland. A forced 4-month drought was introduced with very-high-resolution imagery taken every 2 hours, capturing details of the vertical backscatter patterning through the peat at the centimetric scale. The results showed a clear coherent response both in radar backscatter amplitude and phase to change in water table level and soil moisture. Similar responses were seen across all polarizations. Phase demonstrated a coherent and deterministic change across the experiment; the average differential phase increase across all polarizations was 118° for 17 cm of water table drawdown. Interpreted as the physical movement of the surface, this corresponded to 8.3 mm of surface subsidence. Both phase and amplitude changes were near-linear with changes in the water table depth; amplitude showed a correspondingly strong concomitant mean decrease of 7 dB across all polarizations during the experiment. The results demonstrate the close sensitivity of radar backscatter to hydrological patterns in a peatland ecosystem. The phase result, in particular, strongly supports the notion that differential phase from satellites can be utilized to measure ground deformation as a proxy for the hydrological state.

Time Series Multi-Sensors of Interferometry Synthetic Aperture Radar for Monitoring Ground Deformation

A stack of images is a prerequisite for the multi-temporal interferometric synthetic aperture radar (MT-InSAR) due to the wrapped nature of the interferometric phase. Although the SBAS technique can relieve the requirement of the amount of SAR data, dozens of SAR acquisitions could be regarded as the minimum requirement. However, due to the limitation of the imaging capability of the spaceborne SAR system, the amount of available SAR data acquired from only one SAR sensor is often not enough to satisfy the requirement for phase unwrapping based on the Nyquist sampling assumption. Fortunately, there sometimes may be more than one SAR stack, that is, stacks of SAR data acquired from different SAR systems. In this study, we propose a methodology to detect ground deformation by combining multiple SAR images acquired from different satellite systems for MT-InSAR analysis. First, the low-pass deformation is estimated based on time series SAR acquisitions with low spatial resolution and long wavelengths such as ENVISAT ASAR (ASAR). This information is then incorporated into the processing of time series of SAR acquisitions with high spatial resolution and short wavelength, such as TerraSAR-X (TSX). Specifically, the low-pass deformation will be subtracted from each differential interferogram generated from short-wavelength SAR images, and the rest of the MT-InSAR analysis will be based on the double-differentiation interferograms. Then, the residual deformation will be calculated from these double-differentiation interferograms and together with the low-pass deformation forms the full deformation. As the principal component of deformation has already been subtracted, the phase gradient of those double-differentiated interferograms will be smooth enough to facilitate the phase unwrapping. Between January 2009 and September 2010, 14 ASAR images and 11 TSX images acquired from Tianjin, China are selected as the test data. A root means square error (RMSE) of 9.1 mm/year is achieved from 11 TSX images, while a root means square error of 3.7 mm/year is achieved from 14 ASAR images. However, an RMSE of 1.6 mm/year is achieved when integrating 11 TSX images and 14 ASAR images for MT-InSAR analysis. The experiments show that the proposed method can effectively detect ground deformation.

A two-grid simulation framework for fast monitoring of fault stability and ground deformation in multiphase geomechanics

We present a simulation framework for fast monitoring of fault stability and ground deformation in multiphase geomechanics and demonstrate its efficacy for a joint CO2 sequestration and enhanced oil recovery case study. Fault stability is estimated by tracking the time evolution of the change in Coulomb Failure Function at critical points on the fault. The staggered solution algorithm for the coupled problem is augmented with a feature that allows for the flow and geomechanics sub-problems to be solved on two different unstructured tetrahedral grids. We demonstrate the accuracy of the two-grid method on the classical Mandel's problem. For the field scale problem, the geomechanics grid extends to the ground surface while the flow grid is truncated at a depth above which no well activity occurs and the flow field can be assumed to remain unperturbed. This framework reduces the computational burden associated with initialization of pressure and stress fields in the overburden, allows for a study of the critical interaction between overburden and faults, allows for fast renditions of flow-induced ground deformation, and allows choosing flow and geomechanics grid resolutions independently to capture disparate length scales of the underlying physics.

A spatio-temporal temperature-based thresholding algorithm for underground coal fire detection with satellite thermal infrared and radar remote sensing

Coal fire is a global catastrophe that causes resource waste, economic loss, and environmental pollution. Accurate detection of surface abnormalities induced by coal fires (such as thermal anomalies and land deformation) is critical for coal fire monitoring and extinguishment. However, the conventional thermal anomaly detection methods do not consider the temporal variation of land surface temperature (LST). Moreover, previous studies have not applied the polarimetric persistent scatterer interferometry(PolPSI) technique for coal-fire-related ground deformation monitoring, which is supposed to have better performance than conventional persistent scatterer interferometry (PSI) approaches. To this end, in this study, a spatio-temporal temperature-based thresholding (STTBT) algorithm is proposed to detect thermal anomalies, firstly. Then, the ground deformation obtained by the PolPSI method is combined with the detected thermal anomalies for the coal fire detection. Besides, a two-stage bandpass filter is employed to assist in detecting the suspected coal fire. The results in the Fukang coal fire area, China, demonstrate that, compared with the conventional methods, the proposed STTBT mothed achieves higher accuracy of thermal anomalies detection, thereby can able to detect coal fire areas more effectively. In addition, PolPSI has better performance than PSI in ground deformation monitoring over coal fire areas. The proposed STTBT combined with PolPSI can serve as a powerful tool for detecting and monitoring underground coal fires.

GROUND DEFORMATION ANALYSIS USING BASIC PRODUCTS OF THE COPERNICUS GROUND MOTION SERVICE

Abstract. Monitoring ground deformation at national and regional level with millimetre-scale precision, nowadays, is possible by using Advanced Differential Interferometric SAR (A-DInSAR) techniques. This study concerns the results of the European Ground Motion Service (EGMS), part of the Copernicus Land Monitoring Service, which detects and measures land displacement at European scale. This Service provides reliable and consistent information regarding natural ground motion phenomena such as landslides and subsidence. The ground motion is derived from Synthetic Aperture Radar (SAR) time-series analysis of Sentinel-1A/B data. These data, which provide full coverage of Europe from two different observation geometries (ascending and descending) every six days, are processed at full resolution. The paper is focused on the exploitation of the basic product of EGMS for both regional and local purposes. Analysing the slope and aspect of the deformation field is the novelty of this investigation. In particular, the focus is put on the generation of wide-area differential deformation maps. Such maps indicate the gradient of the deformation field. The obtained information is not only beneficial for monitoring anthropogenic phenomena but also vital for urban management and planning. Most of the significant damages to manmade structures and infrastructures are associated with high deformation gradient values. Thus, monitoring the temporal and spatial variations of deformation gradient is essential for dynamic analysis, early-warning, and risk assessment in urban areas. Although EGMS productions are prepared for monitoring at regional level, their resolutions are high enough to investigate at local level. Therefore, this paper considers the local deformations that affect single structures or infrastructures. Local differences in such deformation can indicate damages in the corresponding structures and infrastructures. We illustrate these types of analysis to generate differential deformation maps using datasets available at CTTC.

ANALYSIS OF THE PRODUCTS OF THE COPERNICUS GROUND MOTION SERVICE

Abstract. Radar interferometry has progressed very much in the last two decades. It is now a powerful remote sensing techniques to monitor ground motion. The technique has undergone an important development in terms of processing and data analysis algorithms. This has been accompanied by an important increase of the Synthetic Aperture Radar (SAR) data acquisition capability by spaceborne sensors. A step forward was the launch of the Copernicus Sentinel-1 constellation. This has made the development of A-DInSAR (Advanced Differential Interferometric SAR) ground deformation services technically feasible. The paper is focused on the most important ground motion initiative ever conceived: the European Ground Motion Service (EGMS). This service is part of the Copernicus Land Monitoring Service managed by the European Environment Agency. EGMS involves the ground deformation monitoring at European scale. The service will deliver the first product in May 2022. In this paper we describe some preliminary examples of deformation products coming from the EGMS.

Effects of thermosyphons on the thermal regime and stability of cast‐in‐place piles in permafrost regions on the Qinghai‐Tibet Plateau

AbstractThe thermal effects of cast‐in‐place piles on the surrounding permafrost frequently induce deformation or failure of piles in permafrost regions. Because piles are directly inserted into the permafrost layer, the thermal disturbance of the piles is more straightforward than that of road embankments to the permafrost. Thermosyphons have proven to be effective in stabilizing the embankments of highways and railways in permafrost regions. However, the effects of thermosyphons on the thermal regime and stability of the cast‐in‐place piles remain unclear. The foundation soils of most piles in permafrost regions along the Qinghai‐Tibet Power Transmission Line were cooled by thermosyphons, and the results of a 7‐year‐period monitoring of ground temperature and deformation of a pile are presented in this paper. The results showed that the extent of thawed permafrost during the installation of the pile extended more than 5 m away from the pile. Thermosyphons shortened the refreezing time by more than 2 months. Thermosyphons cooled the surrounding permafrost to temperatures below the ambient ground temperature at the end of the cold seasons, and the temperature difference lasted until the end of the warm seasons owing to cold reserves formed in the cold season. The thermosyphons mitigated the thermal effects of the concrete pile owing to their higher thermal conductivity. Thermosyphons also significantly decreased the rate of active layer thickening around the pile compared to that observed in a natural field under a warming climate. Generally, thermosyphons stabilized the piles during the observation period by cooling the permafrost around the pile and producing a greater adfreeze force to counteract the frost heave force and subsequently support the tower. Additional thermosyphons or insulation measures may be necessary to ensure the long‐term stability of piles, considering a faster degradation of the ambient permafrost than expected. The results may provide insights into the design and maintenance of cast‐in‐place piles in warm permafrost regions.

Monitoring of construction-induced urban ground deformations using Sentinel-1 PS-InSAR: The case study of tunneling in Dangjin, Korea

The construction of underground tunnels can prime or trigger ground subsidence, and thus surface deformation monitoring is required during and post-construction. Freely available satellite data allow significant possibilities for the use of remote sensing techniques, particularly multi-temporal interferometric synthetic aperture radar (Mt-InSAR), for surface deformation monitoring. However, track records and field demonstrations of InSAR-based tunneling-related deformation monitoring are limited, particularly in identifying the spatiotemporal evolution of ground deformation and causal factors thereof from construction activities. Therefore, this study explores the feasibility of using satellite SAR data to monitor the surface deformation associated with different tunnel construction phases. Tunneling-related surface deformation was analyzed using the persistent scatterer InSAR (PS-InSAR) technique and Sentinel-1B SAR data; the PS-InSAR results were compared with those from the conventional leveling method. The velocity map of the study site revealed a localized subsidence trough associated with the construction of vertical shafts and shield tunneling. The cumulative time-series displacement map successfully tracked the spatial and temporal progression of ground deformations related to the phases of tunnel construction activities. The maximum subsidence rate in the radar line-of-sight direction was estimated to exceed 40 mm/yr, with maximum cumulative subsidence of ∼ 200 mm. The results clearly showed that dewatering during tunneling aggravated the subsidence phenomenon. The consequent compaction and consolidation of the compressible soil layers due to the lowered groundwater table were the main causes of subsidence. Our results demonstrate the viability of the PS-InSAR technique based on the C-band Sentinel-1 product as a monitoring method to examine the spatiotemporal evolution of ground deformation patterns during tunneling activities and as a possible preliminary surveying tool to identify ongoing abnormal settlement prior to tunnel construction.

Pinpointing Early Signs of Impending Slope Failures From Space

AbstractA promised potential of spaceborne interferometric synthetic aperture radars (InSAR) is a capability for regularly monitoring ground deformation with millimeter accuracy, for timely forecasting of impending natural hazards such as landslides. The main limitation in InSAR being actually capable of unleashing this potential for hazard prediction is that key precursory ground displacements are, in the majority of cases, a very small subset of the entire big data set provided by the method over large regions. Consequently, pinpointing a single impending failure may become very difficult or impossible. We develop a data‐driven framework that can handle such imbalanced spatiotemporal data based on the concept of outlying aspects mining, to find a subset of features out of a collection of potential features, which best distinguishes the landslide source area from the others. We show that the identified feature subspace can be used to find anomalous areas across multiple spatial scales, such that Sentinel‐1 satellite monitoring points which persistently lie in these areas can accurately detect the location of the Xinmo landslide (China) almost 1 year in advance—without false alarms. In a second case study, we identify the area affected by rockfalls on Stromboli volcano, a task that is generally infeasible with traditional methods applied to InSAR data. With continuing improvements in the spatial and temporal resolution from the new generation of satellites, such as Sentinel‐1, this approach opens the door to reliable and early prediction of failure over a broad range of slope instabilities.

Polarimetric Persistent Scatterer Interferometry for Ground Deformation Monitoring with VV-VH Sentinel-1 Data

With the launch of the Sentinel-1 satellites, it becomes easy to obtain long time-series dual-pol (i.e., VV and VH channels) SAR images over most areas of the world. By combining the information from both VV and VH channels, the polarimetric persistent scatterer interferometry (PolPSI) techniques is supposed to achieve better ground deformation monitoring results than conventional PSI techniques (using only VV channel) with Sentinel-1 data. According to the quality metric used for polarimetric optimizations, the most commonly used PolPSI techniques can be categorized into three main categories. They are PolPSI-ADI (amplitude dispersion index as the phase quality metric), PolPSI-COH (coherence as the phase quality metric), and PolPSI-AOS (taking adaptive optimization strategies). Different categories of PolPSI techniques are suitable for different study areas and with different performances. However, the study that simultaneously applies all the three types of PolPSI techniques on Sentinel-1 PolSAR images is rare. Moreover, there has been little discussion about different characteristics of the three types of PolPSI techniques and how to use them with Sentinel-1 data. To this end, in this study, three data sets in China have been used to evaluate the three types of PolPSI techniques’ performances. Based on results obtained, the different characteristics of PolPSI techniques have been discussed. The results show that all three PolPSI techniques can improve the phase quality of interferograms. Thus, more qualified pixels can be used for ground deformation estimation by PolPSI methods with respect to the PSI technique. Specifically, this pixel density improvement is 50%, 12%, and 348% for the PolPSI-ADI, PolPSI-COH, and POlPSI-AOS, respectively. PolPSI-ADI is the most efficient method, and it is the first choice for the area with abundant deterministic scatterers (e.g., urban areas). Benefitting from its adaptive optimization strategy, PolPSI-AOS has the best performances at the price of highest computation cost, which is suitable for rural area applications. On the other hand, limited by the medium resolution of Sentinel-1 PolSAR images, PolPSI-COH’s improvement with respect to conventional PSI is relatively insignificant.

Wide-area ground deformation monitoring in geothermal fields in western Turkey

The large-scale production and injection of geothermal fluids induce pressure, volume, and temperature gradient changes in the subsurface, which may result in surface deformation as well. Interferometric synthetic aperture radar (InSAR) is a promising utility for monitoring ground surface deformation and inferring subsurface reservoir operations that are difficult to observe directly. This study provides the first wide-area InSAR-derived long-term ground deformation across major geothermal fields in western Turkey. It aims to identify ground deformation hotspots within the geothermal exploitation sites and analyze their relationship with energy production and pumping. In the present study, the whole 2014?2020 Sentinel 1-A and 1-B SAR archive available over the region along ascending and descending orbits was processed using the persistent scatterer interferometry (PS-InSAR) technique. Compaction and land subsidence hot spots caused by fluid withdrawal are found within the geothermal fields. The results indicate that the observed systematic surface subsidence deformation result from the increase of geothermal production during the observation period in western Turkey. The realtime power data of geothermal plants retrieved from the transparency platform of the Turkish energy exchange are related to surface deformation. We estimated the drainage area of the production wells using subsidence deformation, caused by pore pressure decline in the reservoir. The results provide supporting evidence for the systematic monitoring and identification of deformation patterns in spatial-temporal extend can reveal reservoir dynamics and compartments, which are crucial for reservoir characterization and field development plan.

Wide-area ground deformation monitoring in geothermal fields in western Turkey

The large-scale production and injection of geothermal fluids induce pressure, volume, and temperature gradient changes in the subsurface, which may result in surface deformation as well. Interferometric synthetic aperture radar (InSAR) is a promising utility for monitoring ground surface deformation and inferring subsurface reservoir operations that are difficult to observe directly. This study provides the first wide-area InSAR-derived long-term ground deformation across major geothermal fields in western Turkey. It aims to identify ground deformation hotspots within the geothermal exploitation sites and analyze their relationship with energy production and pumping. In the present study, the whole 2014?2020 Sentinel 1-A and 1-B SAR archive available over the region along ascending and descending orbits was processed using the persistent scatterer interferometry (PS-InSAR) technique. Compaction and land subsidence hot spots caused by fluid withdrawal are found within the geothermal fields. The results indicate that the observed systematic surface subsidence deformation result from the increase of geothermal production during the observation period in western Turkey. The realtime power data of geothermal plants retrieved from the transparency platform of the Turkish energy exchange are related to surface deformation. We estimated the drainage area of the production wells using subsidence deformation, caused by pore pressure decline in the reservoir. The results provide supporting evidence for the systematic monitoring and identification of deformation patterns in spatial-temporal extend can reveal reservoir dynamics and compartments, which are crucial for reservoir characterization and field development plan.

APPLICATION OF INSAR TECHNIQUE FOR THE DETECTION OF GROUND DISPLACEMENT IN PENANG ISLAND, MALAYSIA

Slope failure is Penang Island's most critical geohazards that inflict significant economic damage each year. Penang landslide is considered one of the most disastrous landslide regions in Malaysia. The threat to lives and property had been associated with the slope instability issues for decades and continuous rain that usually lasts for hours/days. Earlier research employed simulation and modeling to address this hazard, but InSAR technique has not been fully utilized to quantify Penang Island's movements. It now requires proper monitoring using satellite techniques. Sentinel-1A S-1A images acquired enables Synthetic Aperture Radar (SAR) processing technique looks very promising. The data were processed using a versatile and powerful tool called SARPROZ software. The Permanent Scatterer Interferometric SAR (PS-InSAR) technique was applied to monitor ground deformation in Penang Island, Malaysia, as various deformations have been reported for years. The results of S-1A data show slow ground deformation values ranging between −9.19 mm/yr and -10.00 mm/yr for subsidence pattern and from 5.00 mm/yr to 4.66 mm/yr for uplift behavior. The results with S-1A data confirmed a trend of deformations around the regions. This reflects the improvement of the S-1A datasets for the PS-InSAR analysis in the region. InSAR result was validated using available GPS analysis. The results were also related to some works on physical parameters such as rainfall, slope, geology, and soil properties of the region for comparison. However, the detailed spatial pattern of surface displacement in the middle of the island is not clear as persistent scatterer has a limitation in the vegetated and rural areas.