جستجوی مقالات مرتبط با کلیدواژه « insar » در نشریات گروه « عمران »

Land subsidence is recognized as one of the most perilous natural occurrences, often resulting from human negligence in water extraction, underground mining, and various other factors. This phenomenon poses a significant threat, specifically in sensitive areas such as railway systems, where irreparable damage can transpire. Notably, subsidence-induced cracks have emerged along several railway routes, including Tehran-Mashhad, Tehran-Varamin, and Isfahan to Shiraz, jeopardizing the integrity of these lines. Consequently, comprehensive monitoring of subsidence and deformation in both temporal and spatial dimensions becomes imperative for effective event management. To accurately assess the deformation patterns of such phenomena, a thorough analysis of the instantaneous time series within the study region is essential. In recent times, Synthetic Aperture Radar Interferometry (InSAR) has emerged as a widely adopted technique for precisely measuring crustal deformation.

This study focuses on examining the rate of land subsidence along the railway lines in the Tehran region, utilizing InSAR and Sentinel-1 satellite imagery spanning the period from 2017 to 2020. The analysis involved processing a total of 46 images and generating 158 interferograms through the application of time series analysis and employing the Small Baseline Subset (SBAS) technique. GMTSAR software was used to create a time series and a displacement map from the interferograms.  To ensure the credibility and comprehension of the research findings, diverse datasets were utilized, including the Iranian Permanent GPS Network for Geodynamics (IPGN) data, the data sourced from the Shamim network of the Land Registry Organization, the measurements from piezometric wells, and the soil characteristics derived from drilling boreholes.

The analysis of the interferometry time series reveals the occurrence of subsidence in specific areas within the case study. The most significant subsidence was observed along the Karaj-Kordan and Maleki-Aprin railway lines, with a deformation rate of approximately 139 mm/year along the line of sight (LOS). Notably, the validation process considering the errors associated with each method yielded relatively satisfactory results. Furthermore, an investigation was conducted to explore the relationship between subsidence, groundwater withdrawal, and soil type. This investigation utilized data from 12 piezometric wells located in the Tehran and Karaj plains, as well as information gathered from drilling boreholes in the study region. The overall findings indicate that the primary cause of subsidence in the region is attributed to a decline in groundwater withdrawal.

Upon analyzing the relationship between annual water loss, subsidence, and the soil characteristics within the region, it was determined that the primary cause of subsidence is the withdrawal of groundwater in areas characterized by thick deposits of fine-grained sediments. The proposed approach in this study highlights the effectiveness of utilizing the InSAR technique for initial evaluations of subsidence along linear infrastructures like railway lines. However, it is advised to employ more precise methods in subsidence-affected regions. Given the relatively limited resolution of Sentinel-1 imagery, it is recommended to utilize images with smaller pixel sizes when assessing linear structures such as roads or railways. Additionally, accurate leveling techniques can be employed to enhance the precision and identification of subsidence areas.

The Ghotor doublet earthquake happened on 23 Feb 2020 near Khoy and Salmas cities in west Azerbaijan province of Iran near Iran-Turkey border .The first large event with a magnitude of 5.8 Mww (USGS) happened at 5:52 UTC (9:23 AM local time) and followed by a second large event of magnitude 6.0 Mw (USGS) at 16:00 UTC. The second event inflicted most of the building damages. No surface rupture has been reported for the events. We estimated the areal extent of the surface displacement related to the 2020 Ghotor doublet earthquakes using three sets of C-band imagery from the European Space Agency Sentinel 1A and 1B satellites. Due to small ground displacement, we could not model the fault geometry of the first mainshock. The ascending and descending displacement maps of the second main shock are used to jointly invert the causative fault plane parameters. To obtain the source parameters, we first down-sampled the unwrapped LOS surface displacements by a quadtree algorithm and then inverted the unwrapped interferograms to infer the geometry of a single rectangular plane with uniform slip in a uniform elastic half-space. The fault geometry parameters are location (X, Y, and Depth), size (length and width), orientation (strike, dip, and rake), and uniform slip of the rupture plane. We assume the X, Y, and depth to correspond to the center of the top edge of the rupture plane. We used a nonlinear inversion method as implemented in the open-source software called Geodetic Bayesian Inversion Software (GBIS) released by Centre for Observation and Modeling of Earthquakes, Volcanoes, and Tectonics (COMET). We used Okada‘s (1985) displacement green functions to model the displacement field. The calculated optimal model illustrates a northeast-striking (N24°) left-lateral rupture plane dipping ~86° towards the west. Once the geometry of the fault plane with uniform slip was estimated, we expanded the rupture plane 20 km along-strike and 12 km along down-dip directions and divided it into 1291 individual patches to obtain the distributed slip on the rupture plane. Each patch has a fixed geometry according to optimal source parameters obtained from the nonlinear modeling, and the slip was allowed to vary freely on the fault plane. We used a modified version of the open-source software called FaultResampler 1.4 to apply the linear inversion for calculating slip distribution on the rupture plane. The coseismic rupture concentrates around a center depth of 3 km with a maximum slip of 97±8  cm. Assuming a rigidity modulus of 30 GPa, the geodetic moment is estimated to be 1.517E+18 Nm, equivalent to a moment magnitude of 6.05 Mw.

Given the special situation of Iran in terms of tectonics, it can be claimed that all faults in the country are seismic. Every year, financial and human losses and losses occur, especially in rural areas due to earthquakes. Today, interferometry synthetic aperture radar technology with various capabilities and products in the field of phase and amplitude has become a powerful tool for monitoring movements. Satellite imagery for two-pass (ascending and descending) capture can provide different information about faults. In this paper, seismic fault parameters are estimated by solving the inverse problem with surface displacement field boundary values ​​obtained from InSAR observations. The study of active fault parameters to identify earthquakes and improve their predictability is a topic of interest for geologists. For this purpose, a pair of Sentinel-1 radar images before and after the earthquake have been studied as images of the study area. As the results show, the maximum amount of ground displacement was 19 cm up and 8 cm down. To obtain the fault geometry and slip distribution on the fault plane, these components have been inverted using the genetic algorithm optimization method and the Acada ​​elastic half-space analysis model. The inverse modeling method showed that InSAR is a useful method for estimating the amount of ground displacement due to an earthquake and also determining the parameters of the fault causing the earthquake. Also, there is 1 and 3 cm uncertainty for two observed and modeled data, respectively. This indicates a better accuracy of descending geometry.

Land subsidence can be counted as a vital concern for human beings due to its harmful effects. The impacts of land subsidence can be seen in several forms, such as cracks in buildings, damage of infrastructures (roads and bridges), tilting and damaged houses, and increases in flooding inundation areas (Gumilar et al., 2015). Overusing of water and soil resources, which can threaten nature and human life, is considered as one of the main reasons for some natural hazards like land subsidence.

Land subsidence due to groundwater over-exploitation is a man-made hazard, and identifying those areas vulnerable to subsidence is of undeniable significance. The present study applies the ALPRIFT method to assess the vulnerability of land subsidence in the Marand plain located in East Azerbaijan province in Iran, which has been at the risk of subsidence in recent years. In the framework of this method that has been developed recently, seven incorporated data layers comprise aquifer media, land use, groundwater pumping, net recharge, aquifer thickness, distance from fault, and water table decline. The data layers were prepared by GIS processing, and the prescribed rates were assigned to the data layers. Then, the data layers were prioritized based on the recommended weights, and the vulnerability map of the region was delineated. In this paper, with respect to the significance of water table decline, two strategies were used in the process of preparing this data layer. In the first strategy, the difference in water levels was used in the first and the last months of a specific year. Based on this strategy, the decline of water table was prepared during 2011-2018. In the second strategy, the trend or slope of water table decline during the same period was used to prepare this data layer. The goodness-of-fit for the vulnerability map and InSAR processing were evaluated by ROC curve. The comparison of the results showed that the estimation of subsidence vulnerability by the first strategy varied for different years; however, the second strategy provided the vulnerability to subsidence regardless of seasonal and temporal fluctuations. Moreover, the result revealed that the southeast and southwest parts of the plain, the Marand city and the Yamchi and Kushksaray residential areas were located in the vulnerable area to subsidence. Moreover, the average subsidence in this plain is 2 cm based on the results of InSAR processing during 2017-2018. The results of this research can be utilized in the planning and management of groundwater abstraction to control subsidence.

Dams are one of the most important fundamental structures all around the world. Given the high volume of water in the dams, they are susceptible to damage and destruction, leading to large financial losses and fatality. Therefore, by installation of instrumentation data in the dam’s body and execution of terrestrial surveying network, stability and safety of dams can be monitored. However, occasionally abnormal processes take place in the dam’s body and foundation that do not match with the instrumentation data’s outcomes. In the recent years, with the evolution and progress of radar imaging techniques and the image processing approaches, large deformations in the dams’ and bridges’ body can be monitored precisely. In the current study, the abnormal deformation and displacement taken place within the time period of Sentinel-1A 2014-2018 on the downstream part of Taleqan dam’s body were evaluated 4 mm/y and were compared with instrumentation data. The results imply that the occurred displacement is related to the external and protective layer of the dam’s body (Riprap) and has no correlation with the dam’s body behaviour.

A number of regions around the world have suffered severe subsidence due to groundwater withdrawal. Mashhad as one of the largest municipalities in Iran has suffered subsidence due to deep groundwater overextraction. Land subsidence in this area can be destructive for urban infrastructures and can create serious environmental issues and structural damages. So, the aim of this research is to precisely determine the uninterrupted vertical subsidence in Mashhad by Permanent Scatterer InSAR technique and also to assess the previous reports on the study area. We complement previous works using more accurate data and procedure in an urban area. Furthermore, we considered geotechnical properties which was not focused in the previous studies. For this purpose, 69 descending and ascending C-band radar images, provided by relatively high-resolution Sentinel-1A satellite, were used to estimate the deformation-trend of the interest area. The method was applied to the images spanning October, 2014, and February, 2017 investigating land subsidence. The assessment procedure demonstrated a high-rate of subsidence in northwest of Mashhad with the significant deformation of 140 mm/year. The outputs were validated using in-situ measurements data and hydraulic head variations respecting piezometric data from groundwater wells. Subsequently, the geotechnical properties of the chosen area were considered to interpret the results. It was illustrated that the land subsidence in the case study is brutally continuous and there is no decrease on the deformation rate.

Landslide is one of natural hazard which often occur in mountainous regions with high precipitation and seismic activity. Iran because of having vast mountainous areas is one of susceptible countries in occurrence of landslide. Case study area of this paper is an instable slope which a village named Gougerd is located on downstream of it. This village is located near Khoy city northwest of Iran in western Azerbayjan province. The purpose of this study is using two different methods in the Geomatics field in order to monitor the probable downward movement of the Gougerd village slope. Differential SAR interferometry (DInsAR) and Global Positioning System (GPS) observation is used as beneficial tools to evaluation and monitoring of surface displacement caused by landslide. 24 SAR images are provided spanning 2003-2010 for InSAR technique processes to study past mechanism of Gougerd slope. Displacement field map and time-series of selected PS pixels are the final products of InSAR analysis which show the range of the occurred mass movement along sensor line-of-sight. Also in order to more accurate evaluation and consideration a geodetic network with ~ 20 stations are constructed on the slope. Dual frequency GPS receivers are applied to do geodetic observations of this network to study present mechanism of the slope by determining the precise horizontal movement at some specific sparse locations. Static mode of GPS observations is done in 3 epochs during 2010-2011 with time interval of about 7 month. Using DInSAR technique beside GPS Geodetic observation method released useful qualitative and quantitative information about downward movement of Gougerd slope. Displacement analyses of both used methods represent significant movement especially on the upstream of Gougerd slope affected by landslide creeping. GPS and InSAR results showed suitable compatibility and prove that these two methods are complementary each other appropriately to illustrate surface slow movement like landslide creeping as we used it in this research.

Recently, Interferometric Synthetic Aperture Radar (InSAR) has proven to be a very effective technique for monitoring and measuring earth surface deformations,such as subsidence, landslide, volcanic and other tectonic deformation. InSAR observations are based on measuring the differences in received phases of SAR images which covers the same area.Almost, any interferograms covers areas where the signals decorrelate, so measurements in these regions are not reliable. This problem is due to temporal and spatial decorrelation and alsodifferences in atmospheric delay between imges. There are two main techniques to overcome the mentioned limitations: Small Baseline Subsets (SBAS) and PersistentScatterer Interferometry (PSInSAR).This paper investigates land subsidence due to ground water exploitation in Tehran Plain by means of PSInSAR. Envisat datasets between 2003 and 2004 are used.To evaluate the results, the InSAR subsidence rate and time series are compared with spirit leveling measurements.