Specifics in the formation of substituence through in the Karvina part of the Ostrava-Karvina coalfield with the use radar interferometry

Deep extraction of minerals is accompanied by deformations of the strata overlying extracted coal seams. Deformations of overlying layers run up to the surface where a subsidence trough gradually forms. The movement of individual surface points is curvilinear, spatial and, in relation to the time pattern, not uniform. In some cases, during the formation of a subsidence trough, temporary uplifts of the surface occur. This paper gives a particular area in which uplifts of the surface occurred when the rigid overlying strata was disturbed. The character of deformations of the overlying rocks is evaluated on the basis of a comparison of the results of the measurement of subsidence of the surface using geodetic methods with the development of mined-out areas and with their extracted thickness. For specifying the time of failure of the overlying strata, also information obtained from a system of continuous monitoring of seismic events is used. The spatial extent of the subsidence trough is identified by satellite radar interferometry (InSAR) techniques applied to TerraSAR-X images. The subsidence wave was possible to detect using a short temporal difference of 11 days between satellite radar images. This shows the potential of short-temporal high resolution InSAR for monitoring of progress of subsidence troughs. A good knowledge of extents and shape of subsidence trough formation in time allows to verify values of parameters used for prediction purposes. Application of the short temporal InSAR appears very effective for spatio-temporal studies of the current subsidence trough development and helps understanding the physical process as well as identifying deviations from the behaviour expected by models.Web of Science13326926

Optimization of satellite insar techniques for monitoring of subsidence in the surroundings of Karvina mine: Lazy plant

This paper deals with issues related to convenient monitoring of subsidence due to longtime mining activities of Czech Karviná Mine: Lazy plant, using satellite SAR interferometry (InSAR) techniques. It maintains approaches for optimizations of differential InSAR, especially including available filtering possibilities. It was realized that current SAR satellites were not able to appropriately evaluate deep subsidence as it occurs in Czech mining sites. Other issues are related to the presence of dense vegetation. Data from previous and only available L-band SAR satellite ALOS demonstrates its high potential in this area of interest. However, only a few acquisitions are available of the mining site disallowing usage for purposes of continuous monitoring of subsidence in the area. Processing results of InSAR techniques of the Lazy plant are presented in this paper.Web of Science101656

Present-day kinematics of the Southern Eastern Alps

The European Alps exhibit extremely low (<2 mm/yr) horizontal deformation rates caused by the anticlockwise rotation of the Adriatic lithosphere. Uplift peaks in the Central Alps at 2-3 mm/yr due to post-glacial isostatic rebound, slab tearing and erosion. The subducted Adriatic plate causes N-S shortening on ~E-W trending frontal thrust faults separating the Southern-Eastern (SE) Alps from the densely-populated foreland. Regional seismicity is abundant and includes M6+ earthquakes such as the 1975 Mw6.5 Friuli event. Further north the Eastern Alps extrude towards the Pannonian basin at sub-millimeter rates. Global Navigation Satellite System (GNSS) rates provide a first-order constraint on plate locking, a vital component in seismic hazard assessment. But the geometry of the active faults remains unclear. I present recent deformation rate maps of the SE-Alps in unprecedented resolution (~400 m, 6 days). The rate maps were derived from interferometric (InSAR) small-baseline (SBAS) time-series collected by the European Sentinel-1 radar satellite mission since 2017. Each of the assembled eight 240-km-wide radar tiles contains 300+ acquisition images, resulting in 2000+ interferograms (per tile), which were automatically generated, phase-unwrapped, and corrected for atmospheric and topographic signal contributions. I used the LiCSBAS time-series analysis software that applies a small-baseline (SBAS) approach, accounting for spatio-temporal coherence and seasonality. After tying the individual rates maps into a Eurasian reference frame defined by published GNSS rates I decomposed the rates originally observed in two look directions into east and vertical components. Field surveys, originally scheduled to densify the GNSS network in Slovenia were unfortunately canceled due to the pandemic. The rate maps provide insight on the InSAR signal-detection limit of a challenging region like the heavily vegetated and snow-covered SE-Alps, overprinting subtle deformation signals along N-S, to which radar antennas are least sensitive: The vertical rates reflect a mixture of isostatic, and anthropogenic processes, overlaid by significant soil-moisture bias (Figure 1). The long-wavelength tectonic signal, remained below the detection threshold of the east rates. In comparison, considering only persistent scatterers (PS) produces more significant InSAR signals (cf. Areggi et al., 2023). Based on recently updated GNSS rates (Pintori et al., 2022) I designed a kinematic model of the most active faults of the SE-Alps. I embedded an inter-connected chain of five dislocations in an elastic half-space and activated them in back-slip mode with no constraints on geometry or slip. Using simulated annealing I first scanned the parameter space randomly (Monte-Carlo) then gradually preferred parameter sets with a promising data fit. Such a multi-parameter model would add valuable new information on the unknown geometry of the active faults, also, because accurate earthquake locations of other 4D-MB projects (e.g., Najafabadi et al., 2020; Hofmann et al., 2023) provide ambiguous information on the fault dip. My tests resulted in unstable solutions, suggesting that geometric constraints (cf. Serpelloni et al. 2016) are compulsory in this particular case

Application of satellite radar interferometry (PSInSAR) in analysis of secondary surface deformations in mining areas. Case studies from Czech Republic and Poland

Secondary deformations are ground movements occurring in areas of ceased underground mining. These are associated with delayed readjustment of rock mass resulting in subsidence, discontinuous deformations (sinks, cracks, etc.) due to destruction of underground, usually shallow, workings, and elevation of ground surface in response of rock mass to rising groundwater levels following the end of mine water drainage. Comparative analysis of secondary deformations in two former mining areas in the first period after cessation of underground hard coal mining is the subject of this study. We used ERS-1/2 and Envisat satellite radar interferometry data processed with PSInSAR technique and GIS to map vertical (in satellite's line of sight, LOS) movements of the surface and analyse them in relation to location of coal fields and underground water table rise. In the study, two areas have been compared, the Ostrava city in the Czech part of the Upper Silesian Basin and the Walbrzych Coal Basin in Poland. The results of analyses based on the results of PSInSAR processing between 1995 and 2000 for the Walbrzych site indicate uplift (up to +12 mm/year) in closed parts of coal fields and subsidence (up to nun/year) in areas of declining mining. Results of PSInSAR analysis over the Ostrava site indicate decaying subsidence after mine closures in the rate of up to -6 mm/year during 1995-2000. Residual subsidence and gentle uplift have been partly identified at surroundings of closed mines in Ostrava from 2003-2010 Envisat data. In Walbrzych gentle elevation has been determined from 2002 to 2009 in areas previously subsiding.Web of Science15218517

Multitemporal monitoring of Karvina subsidence troughs using Sentinel-1 and TerraSar-X interferometry

Satellite SAR interferometry (InSAR) allows to observe borders of subsidence troughs created in undermined areas. There is a possibility to evaluate a subsidence velocity in the accuracy of a mm/year for the stable reflectors of the radio signal, e.g. buildings. We apply Permanent Scatterers (PS) and Quasi-PS (QPS) techniques for monitoring of mine-caused subsidence in the Karvina area situated in the Czech part of Upper Silesian Basin. We use PS technique as effective for observation of displacements of built structures (e.g. buildings) and QPS for monitoring of spatio-temporal development of subsidence troughs. The results reveal information valuable for an identification of deviations from expected effects of mining activities on the land surface and for the infrastructure which are potentially affected by the subsidence. We perform the processing of Sentinel-1 and high resolution TerraSAR-X to find how the lower spatial resolution of Sentinel-1 SAR affects the reliability of results. The assets of these new sensors, especially the short revisit time, can overcome the basic limits of InSAR methods connected with temporal lags between available SAR images. In previous Karvina area datasets (ERS, Envisat, Alos satellites) the basic temporal step used to be around one month. During such temporal length significant changes occured in vegetation cover or in cultivated soil causing a loss of coherence of radar measurements. In addition to this, the amount of subsidence of Karvina troughs has often exceeded detection limits of the SAR systems. A significant increase of the reliability of evaluated subsidence also in areas with a moderate vegetation cover is expected with the launch of Sentinel-1B since the short-term interferograms would not be affected by a full decorrelation.Web of Science141595

Deformations of Highway over Undermined Ostrava-Svinov Area Monitored by InSAR Using Limited Set of SAR Images

AbstractPart of Czech highway D1 connecting Ostrava city with Prague and Poland, is built over an undermined area of Ostrava-Svinov, with mines closed since 1991 in the area. Soon after its opening ceremony in 2008, the highway began to exhibit various significant deformations. An attempt of InSAR monitoring using ERS, Envisat and several TerraSAR-X Spotlight acquisitions was done in order to monitor progress of deformations, to consider suitability of satellite InSAR for such purposes and to search for footprints whether the deformations were caused by fading subsidence due to undermining or by another, local, reason. Only shallow subsidence was found in the area from Envisat data ranging 2005-2010. Highway deformations in late 2011 are observable from processing of limited set of 5 TerraSAR-X images using different methods. Detected deformations are very probably due to longitudinal thermal expansion of the observed highway bridge. This publication contains issues to be taken into consideration for appropriate interpretation and processing if the available input dataset is limited and not optimal

Practical Application of Satellite-Based SAR Interferometry for the Detection of Landslide Activity

AbstractAfter two decades of SAR satellite operation, their data, processed by interferometric techniques (InSAR), allows for a sensitive detection of terrain movements. Various projects have risen towards the detection of landslide activity and thus possibility of early warning system based on SAR data. The ability of InSAR techniques to detect a slope stability is limited and depends on slope orientation, movement rate, vegetation cover and temporal and spatial image resolution. This paper presents common issues found in past projects of the team of authors observing landslides using available satellite SAR data processed by various InSAR techniques. It is demonstrated that in some cases the basic differential InSAR combining only two images provides more valuable information compared to advance multi-temporal InSAR techniques.The paper aims at providing guidelines for maximal successful detection of landslide activity and to introduce pros and cons of the InSAR method, which often discussed in geology and geophysics circles. We prove the potential of techniques using satellite-based InSAR to identify creeping movement of structures built at moving slopes and the limited possibility to detect movements at moderately vegetated slopes by using especially the L-band or a combination of winter-season SAR and other images within very short temporal difference. It is possible to overcome misinterpretation of results by proper understanding of InSAR source phase component at slopes, including phase distortions due to SAR geometry, vegetation movement (vegetated mass movement) and atmospheric pressure changes correlated with height differences

Identification of ground instability in the housing estate complex based on georadar and satellite radar interferometry

Procedures of using ground penetrating radar (GPR) and Sentinel-1 satellite synthetic aperture radar (SAR) were tested in the area of housing estates in Hodonin, where there is an intensive decrease in the subsoil and thus a significant cracking of prefabricated houses. Extensive geophysical research of the site provided essential information about active faults in the area. To prove them and define the most active deformation zones (blocks), where the maximum settlement of the subsoil occurs, the processed interferometric (InSAR) data from the Sentinel-1 SAR satellite were used. Results from joint evaluation of geophysical data and InSAR not only confirmed detected deformations but also notified on other locations with tendencies to subsidence in the neighborhood of main faults. The combination of the methods to identify displacement tendencies in urbanized areas is very effective.Web of Science18224023

Monitoring non-linear ground motion above underground gas storage using GNSS and PSInSAR based on Sentinel-1 data

Several methods allow accurate measurement of terrain surface motions. Global navigation satellite systems (GNSSes) and interferometry with synthetic aperture radar (InSAR) stand out in terms of measurement accuracy among them. In principle, both methods make it possible to evaluate a three-dimensional vector of the motion of points on the terrain surface. In this work, we dealt with the evaluation of motions in the up-down (U-D) and east-west direction (E-W) over underground gas storage (UGS) from InSAR. One crucial step in breaking down PSInSAR line of sight (LOS) measurements to U-D and E-W components is getting time series derived from individual tracks to the same time frame. This is usually performed by interpolation, but we used an innovative approach: we analyzed individual time series using the Lomb-Scargle periodogram (LSP), which is suitable for periodic noisy and irregularly sampled data; we selected the most significant period, created LSP models, and used them instead of the original time series. Then, it was possible to derive time series values for any arbitrary time step. To validate the results, we installed one GNSS receiver in the Tvrdonice UGS test area to perform independent measurements. The results show a good agreement in the evaluation of motions by both methods. The correlation coefficient between horizontal components from both PSInSAR and GNSS was 0.95 in the case of the E-W component, with an RMSE of 1.75 mm; for U-D they were 0.78 and 2.35 mm, respectively. In addition to comparing the motions in the U-D and E-W directions, we also created a comparison by converting GNSS measurements to a line of sight of the Sentinel-1 satellite to evaluate the conformity of InSAR and GNSS measurements. Based on descending track, the correlation coefficient between LOS from both methods is, on average, 0.97, with an RMSE of 2.70 mm.Web of Science1419art. no. 489

Neural network-based urban change monitoring with deep-temporal multispectral and SAR remote sensing data

Remote-sensing-driven urban change detection has been studied in many ways for decades for a wide field of applications, such as understanding socio-economic impacts, identifying new settlements, or analyzing trends of urban sprawl. Such kinds of analyses are usually carried out manually by selecting high-quality samples that binds them to small-scale scenarios, either temporarily limited or with low spatial or temporal resolution. We propose a fully automated method that uses a large amount of available remote sensing observations for a selected period without the need to manually select samples. This enables continuous urban monitoring in a fully automated process. Furthermore, we combine multispectral optical and synthetic aperture radar (SAR) data from two eras as two mission pairs with synthetic labeling to train a neural network for detecting urban changes and activities. As pairs, we consider European Remote Sensing (ERS-1/2) and Landsat 5 Thematic Mapper (TM) for 1991-2011 and Sentinel 1 and 2 for 2017-2021. For every era, we use three different urban sites-Limassol, Rotterdam, and Liege-with at least 500 km(2) each, and deep observation time series with hundreds and up to over a thousand of samples. These sites were selected to represent different challenges in training a common neural network due to atmospheric effects, different geographies, and observation coverage. We train one model for each of the two eras using synthetic but noisy labels, which are created automatically by combining state-of-the-art methods, without the availability of existing ground truth data. To combine the benefit of both remote sensing types, the network models are ensembles of optical- and SAR-specialized sub-networks. We study the sensitivity of urban and impervious changes and the contribution of optical and SAR data to the overall solution. Our implementation and trained models are available publicly to enable others to utilize fully automated continuous urban monitoring.Web of Science1315art. no. 300