جستجوی مقالات مرتبط با کلیدواژه « تداخل سنجی راداری » در نشریات گروه « جغرافیا »

Morphometric study of a watershed plays a very important role in land structure. Remote sensing methods provide a good tool for studying and extracting stream networks. One of the common methods for extracting waterway networks and conducting a morphometric study of watersheds is the use of Digital Elevation Models (DEMs) with a high spatial resolution. The purpose of this study was to extract stream networks by using the DEMs of high spatial resolution, such as ALOS-1 and Sentinel-1, and those of medium spatial resolution like SRTM and TanDemX. To produce the DEM by using Sentinel-1 images, the InSAR method was applied. Finally, to validate the accuracy of this DEM for checking Sentinel-1 ability to extract stream networks, the ALOS-1 DEM with the spatial resolution of 12.5 m was used. The results revealed that the produced DEMs by using Sentinel-1 images had a high correlation of about 0.99 with the reference data of ALOS-1, thus showing the high capability of the DEM for extracting stream networks. The results of extracting the waterway networks demonstrated that each of the two DEMs of Sentinel-1 and ALOS-1 with high spatial resolutions could extract 9 waterway networks, while the digital models of SRTM and TanDemX with medium resolutions could only extract 7 and 6 stream networks, respectively. The studies indicated that the baseline parameters, as well as the time difference between the two Master and Slave images in InSAR, had to be highly considered by researchers to improve the quality of the Sentinel-1 DEM.

 Interferometric Synthetic Aperture Radar (InSAR) is a powerful instrument in estimating subsidence with millimeter accuracy. This article uses Sentinel 1A satellite data from 2016 to 2020 to monitor subsidence in Fasa plain. The results of radar interference studies showed that 24 cm subsidence occurred in the study area during the statistical period. In order to find the cause of subsidence, information of piezo metric wells in the area was collected and their changes during the period 1372-1399 were studied. According to the results, the groundwater level in areas with land subsidence has been associated with a decline. Especially in the villages of Dastjeh, Sahravard and Ghazi Kouchak, which have the highest rate of groundwater level drop and are in the zone of high subsidence risk. The lands of the region mostly include gardens and irrigated cultivation. In this regard, it can be said that one of the main reasons for land subsidence in the study area is the uncontrolled abstraction of groundwater resources

One of the types of domain instability that causes financial and human losses every year is the risk of landslides, which has social, economic and environmental consequences. The basin of Balharud Shahrestan is one of the areas prone to landslides due to its mountainous nature and steep slopes. Investigating the effective factors in the occurrence of landslides and identifying the prone areas is an important step in managing natural resources and achieving sustainable development. Radar interferometric technique is an effective method in measuring ground surface displacement. This technology has become very common in the investigation of natural hazards of the earth, such as mass movements of slopes, subsidence, earthquakes and volcanic activities. In this research, in order to identify and measure landslides, Sentil 1 radar images of 2020 and 2022 have been used. In order to process information, SARSCAPE software has been used, and the maximum landslide displacement in the opposite direction was estimated to be 0.154 cm, which was observed along the fault lines and in the center of the study area. Also, the results of this research showed that radar images have a good potential for revealing the instability of domains and calculating their displacement.

In the last decade, subsidence is occurring as a geomorphic hazard in a large part of Iran's plains, including Mashhad plain as one of the important plains. Investigating the subsidence rate and dealing with the causes and influencing factors for risk management is very important. Radar interferometry technique is a powerful tool in estimating subsidence with millimeter accuracy using phase observations. In this paper, 2017-2021 Sentinel 1A satellite data used in order to monitor the subsidence that occurred in Mashhad plain. The results of radar interferometry studies showed that 64 cm of subsidence occurred in the study area during the statistical period.The information of piezometric wells in the collection area and their changes during the period 1991-2019 were examined in order to find the cause of subsidence. The water level of the wells has reached its maximum decrease in the studied period. The highest drop in the groundwater level has occurred in the central and southeastern regions of the studied area. The lands of the region mostly include gardens and irrigated cultivation. In general, the highest rate of subsidence has been created in areas with a sharp drop in the groundwater level, fine-grained soil texture, and high alluvial thickness.

Land subsidence is one of the ecological crises that especially cause damage to human facilities such as communication networks and buildings. Many factors affect the subsidence of the earth, and earthquakes can be one of those factors. The current research examines the effect of the November 2017 earthquake in the western region of Kermanshah on subsidence. For this purpose, the differential radar interferometric method and Sentinel 1 satellite data have been used to investigate the subsidence of the region. Pair processing of radar images in the study area between 11/11/2017 and 11/30/2017 showed that the amount of vertical displacement in the study areas is between -41.72 and -42.99 cm. According to the obtained results, the average displacement of subsidence in the opposite direction of view is -304.16 and -33.1265 cm, which was observed along the fault lines. Also, the average uplift movement rate in the studied area is 17.53 and 34.53 cm per year in line with the satellite view. The evaluation of the displacement map of the region shows that the greatest amount of subsidence was in the eastern, southern, and western parts of Salas Babaji City and the southern and western parts of Sarpol-Zahab city.

The risk of subsidence can be an important factor in increasing the vulnerability of the center of human activities located in areas with natural hazardous infrastructure such as earthquakes. In recent years, this phenomenon has caused a lot of damage to the plains and cities of Iran, especially to residential buildings, plains and agricultural lands located in Chaharmahal and Bakhtiari provinces. Therefore, monitoring the amount of subsidence and dealing with its influential causes in order to control and manage its vulnerability is of particular importance. So far, various methods have been used such as using GPS, precision instrument alignment and radar interferometric method to measure land subsidence. In the meantime, the radar interferometric method is an up-to-date and effective technique for measuring changes in the earth's surface worldwide. In this article, satellite data and radar interferometric technique have been used to measure the subsidence risk of Lordegan plain and urban settlements. For this purpose, the amount of subsidence in a period of 6 years (from 2017 to 2023) has been evaluated using Sentinel A1 data using SNAP software. The results of field observations indicate that the occurrence of subsidence and proportionally the drop of groundwater level is due to excessive extraction of underground water. The data obtained from the piezometric wells of Lordegan city and Barm spring indicate a sharp drop in the underground water level since 2008. The amount of groundwater dropping has been observed in some areas up to 15 meters. The results obtained from the radar data showed that during a 6-year period, Lordegan city has experienced an amount of subsidence of about 14 to 18 cm. These subsidence amounts are about 3 cm per year, which is at the warning level and beyond the normal state. So, accurate management of the withdrawal of underground water seems essential by considering the significant rate of subsidence and its risk.

Radar images obtained from virtual aperture radars (SAR) with the ability to measure the length of the vector from the sensor to the ground surface, are widely used in measurements related to the preparation of digital elevation maps. The technique used in this method is known as radar interferometric technique (InSAR). In radar interferometry, the phase obtained from two images taken from a certain area is interfered to produce an interferometer. In fact, the interferogram is the different product of two radar images. In the interferometry method, the mixed radar images that have the return phase values from the complex to the sensor are combined with each other and an image called the interferometer is produced. Hence, interference is obtained from the phase difference of two images taken at two different times, which are geometrically precisely matched. By using the phase difference information available in the interferometer, which indicates the distance difference between the sensor and the object, it is possible to prepare the deformation variable of the earth's surface or earth's topography. In this research, C-band radar images of the European Space Agency's Sentinel-1A satellite were used in the period of 02/05/2017 to 01/29/2023 at the level of a SLC and in IW mode with high resolution with VV polarization. In addition, in the data processing stage, sub-band IW1 and segment 2 to 3 images were used.

The radar interferometry method measures changes in the earth's surface along the line of sight of the satellite. Due to the fact that the major changes in the land surface in subsidence are in the form of height changes, the displacements extracted by the radar interferometric method can be converted into height changes by ignoring the horizontal changes in the ground surface and depicting them in the vertical direction. Each interferogram individually only contains surface changes in one time interval. By using a number of interferograms along with time series analysis, surface changes can be examined over time. Analysis of time series using radar interferometric method is a suitable method for estimating the rate of land surface changes in high spatial resolution. By having two images with different time intervals from satellite images, the rate of subsidence and vulnerability of an area can be calculated at any point and date with the radar interferometric method. It is worth mentioning that the radar interferometry technique is one of the most up-to-date and accurate tools for calculating the rate of land surface changes in the world and is being used all over the world.

In this article, using the radar interferometric technique, the state of the subsidence phenomenon in Lordegan city and the damages caused around the Barm spring in Lordegan city have been discussed. In summary, the most important results obtained are:• The results obtained from the rainfall data and different hydrographs of the plain showed that, the amount of rainfall and the level of underground water have significantly decreased since 1986, for example, the level of underground water has decreased from a depth of about 15 meters from the ground surface to a depth of about 33 meters. The results of the radar interferometry technique to depict the range of subsidence, showed that the total maximum amount of subsidence between the years 2017 and 2023 was about 18 centimeters, which is about 3 centimeters of annual subsidence. based on the evidence and investigations carried out on the Barm spring in Lordegan city, it was determined that the volume of water spring has significantly decreased. It should be noted that the construction of heavy structures and other constructions near the spring has also affected the water flow and the reduction of the flow of this spring. In recent years, numerous damages have appeared in the city and around the Barm spring, for example, the appearance of numerous and annual cracks on the streets and the path of the old aqueducts, cracks and damage to the stone walls around the spring, damage to buildings.

As a morphological phenomenon, land subsidence is a type of change in the shape of the earth's surface, which is associated with a vertical deformation or downward movement of the earth's surface, as well as the gradual settlement or removal of surface materials. The phenomenon of subsidence is due to various causes, including natural factors such as earthquake, volcanoes, fault activities, subsidence due to rising sea levels, dissolution in rocks or following human activities, including; Indiscriminate removal of fluids from the ground, such as; Water, oil and gas occur. The environmental consequences of the subsidence phenomenon are irreversible, costly, and destructive, and include creating a gap on the surface of the earth, damaging human structures, etc. Foundations, streets, bridges, roads and power and sewage transmission lines, destruction of irrigation systems and fertile agricultural soils and damage to wells. According to the statistics announced in Iran, the adverse effects caused by subsidence are not low and are rapidly developing and spreading in different plains across the country, and the lack of timely management and control of its factors can cause loss of life. And leave an irreparable loss.

In this research, the images of Sentinel 1, which captures images in the C-band range of microwaves, have been used. Then the necessary processing was done through the SARSCAPE 5.2 plugin in ENVI 5.3 software and the technique used in this research to determine the amount of subsidence is the differential interferometric method with the combined opening of two frequent or non-frequent passes. In radar interferometry, the phase difference of two images from a specific time zone and baseline is determined. To zone the risk of subsidence, in the stage of data collection, the influencing components must first be specified and the required data and information must be collected and classified based on them. For this purpose, in this study, first, the effective factors (including slope, lithology, land use, precipitation, distance from the city and village, distance from the river, distance from the fault, and drop in the underground water level), according to the natural and human conditions of the region was identified. In the next step, information layers related to each of the factors were prepared in the geographic information system environment. In the next step, the weighting of the investigated factors was done according to the Critic method, and the final analysis was done using the Aras method.

After the interferometry steps, the phase difference has been converted into vertical displacement in the metric system. During the surveys conducted, the amount of subsidence between the years 2016 and 2020, during the last 5 years, shows that according to the above map, the highest amount of subsidence in the central, north-western, and north-eastern parts, amounting to 0.37 mm, it is concentrated. Investigation and analysis of land use and subsidence map and field studies confirm the maximum occurrence of subsidence in agricultural areas, and urban and rural areas, respectively. The presence of fertile plains and the flow of the Qarasu river in Namin city has provided a good opportunity for agricultural and animal husbandry activities, and the areas with agricultural land use have a high potential for subsidence due to the exploitation of underground water areas. After extracting the maps of each of the criteria and applying the relevant weights obtained by the Critic method and by implementing the different stages of the Aras technique, the maps of the subsidence risk zoning in 5 categories from very high to very low risk The risk is achieved. According to the result of using the Aras method, 168.01 square kilometers of the range area is in the very high-risk class and 222.31 square kilometers is in the high-risk class. Most of the high-risk and high-risk class in terms of the possibility of subsidence is located in the central and semi-western parts. Examining the high-risk and high-risk points introduced by the Aras algorithm shows; In terms of the criteria of land use, agricultural use, urban and industrial areas account for the largest percentage of the area of areas with very high and high risk. According to the land use map of the study area, a major part of the city's land has been allocated to agricultural use, which has caused overexploitation of the underground water table in recent years. In addition, a large part of the water needed for drinking and the industrial sector is also supplied from underground water sources, and this, in turn, is involved in the reduction of the water level and the increase in the risk of subsidence in the studied area.

The evaluation of the subsidence rate of the region shows that the highest subsidence rate was in the central, north-west, and north-east areas of the range and the results show that the trend of the groundwater level drop is consistent with the subsidence rate and in the areas where the water level drop is the highest. has existed, the amount of subsidence has also been higher. According to the results of subsidence risk zoning; The criteria of water level drop, and land use, respectively, with a weighting factor of 0.186 and 0.168, were assigned the most weight, and therefore, it can be said that the most important factor involved in increasing the amount and potential of subsidence in the study area of exploitation. It is a waste of underground water. Finally, it can be acknowledged that because land subsidence can cause irreparable financial and human losses, long-term solutions in the form of modifying water resources management methods and short-term solutions in the form of prevention From extraction of underground water tables, creating of underground dams to increase the water level, curbing surface water and implementing artificial feeding plans, confiscating unauthorized drilling equipment, preparing and installing smart meter devices, organizing drilling companies, strict control of water consumption and change The consumption pattern should be taken into consideration by relevant officials as well as residents.

The shape of the earth changes over time and these changes can be periodic or non-periodic. Land deformation may be related to tectonic processes such as earthquakes, faults, volcanoes, landslides, and anthropogenic processes such as mine activity and groundwater exploitation. Subsidence and uplift is one of the most important changes in the shape of the earth. Which is directly related to the tectonic status of the areas. Which is directly related to the tectonic status of the areas. The land of Iran as part of the active alpine-Himalayan tectonic zone has been affected by numerous tectonic activities over time, with the emergence of the Zagros-Makran and Alborz-Kope-Dagh mountains in the Iranian plateau due to the Arabian-Indian Plateau drifting from the landforms resulting from this convergence. Kermanshah plain is also active in tectonic terms due to its location in folded Zagros, therefore it has a lot of potential for the displacement of the Earth's surface. Today, the calculation of ground-level displacements using radar interference technology includes unique capabilities in terms of dimensions, cost, time and accuracy compared to other measurement techniques. Accordingly, in the present study, radar interferometry method was used to assess the amount of subsidence and uplift of Kermanshah Plain and the correlation of this displacement with the earthquake in Kermanshah on 21/08/1396.

Nowadays, calculation of displacements occurring on the surface using radar interferometry technology has unique capabilities in terms of size, cost, time and accuracy compared to other measurement techniques. Therefore, in the present study, using radar interferometry method and SBAS time series, the vertical displacement rate of Kermanshah plain and its relationship with 7.3 earthquake of Kermanshah Ezgele have been investigated. In this study, the displacement rate was calculated for three periods:-the first time in the history of 11.24.2016 to 11.07.2017 and includes 13 image Sentinel 1.Second period is from the date of 07/11/2017 to 11/19/2017 (before and after the earthquake). The third time frame selected to assess the impact of the earthquake on the process of changes and calculations for different purposes is from 24/11/2016 to 19/11/2017 (including 2 images).

The results show that the Kermanshah herd earthquake has a direct role in the vertical displacement of Kermanshah plain. The result of calculating the vertical displacement in the first period indicates that the northwest and southeast areas of Kermanshah urban area have subsided and the northeast and southwest elevations have been elevated, but this trend has changed due to the earthquake of the Ezgele, So that the earthquake of the Ezgele has increased many parts of the study area, especially its southern regions, and has also subsided in the northeast areas of the study area, so the results in the third time period have been very variable, It is concluded that the Kermanshah northeast highlands, which had been uplifted during the first period, were associated with a subsidence due to the Kermanshah herd earthquake. Also the southeastern areas of Kermanshah urban area which had subsided in the first period, Due to the direct impact of the earthquake from the Ezgele, it has been experiencing an uplift in the third period. Therefore, it can be said that the earthquake of the Ezgele, while changing the vertical displacement process of Kermanshah plain, can affect the results of different calculations in this regard.

In this research, in order to investigate the factors affecting this displacement, three time intervals were used to evaluate the vertical displacement of the area. The results indicate that the range of studies ranged from +107 to -40 mm. Given that the amount of positive displacement (uplift) was higher than the negative displacement (subsidence) and also the tectonic factors, the main cause of the displacement can be attributed to the tectonic factors, however, other factors such as groundwater depletion can affect the rate of subsidence in the northwest and southeast of Kermanshah urban area. Evaluation results in the second time period indicate that the study area had a vertical displacement of between +22 to -46 mm during the 12 day period before and after the earthquake, which could be attributed to the short-term period. Directly attributed to the earthquake of the Ezgele. The third study period also had a range of displacements of +102 to +33 mm, but the important and significant point in this period was the impact of the earthquake of the herd on the extent and trend of displacement in the study area. In fact, the results show that in the first period, the northwest and southeast areas of Kermanshah metropolitan area have subsided and the northeast and southwest areas have risen, while the northeast Kermanshah highlands have subsided. The first time has been uplift, during this period has been associated with subsidence due to the Kermanshah Ezgele earthquake. Also, the south-eastern areas of Kermanshah metropolitan area which had subsided in the first period, due to the direct impact of the earthquake from the Ezgele, in the third period has been rising. Therefore, it can be said that the earthquake in Kermanshah plain, while changing the vertical displacement process, can affect the results of different calculations in this regard.

In the early 1990s, radar interferometry was introduced and used as a useful tool in the study of all phenomena that cause land surface deformations. If the land surface deforms between two radar images, a surface displacement map can be created with millimeter resolution and accuracy. This paper reports the findings of the Sentinel1 –A data time series results using the SBAS algorithm to detect surface deformation in the Sangan iron ore mine. Sangan Iron Ore Mine is the largest open pit iron ore deposit in the Middle East. Due to mining activities, this mine has undergone many changes in terms of topography and geomorphology, which can intensify geomorphological processes. To detect and obtain the amount of land deformation, 48 SAR images of Sangan iron ore mine obtained by the European Space Agency's Sentinel 1-A satellite were used. The time series (2014-2020) obtained from the deformation in the range of placer mines were analyzed. The results show the average displacement rate of -20 to -35 mm per year and the maximum cumulative rate of deformations of -120 mm. Investigation of the cross-section in the two parts of the apex and the center of the alluvial fan in the placer mines during the period 2014-2017 shows the topographic changes well. To evaluating the reliability of the results, the results derived from SBAS have been compared due to the lack of data in the range of placer mines with the values measured by the total station related to the mountain unit in the years 2020-2014. The results showed that the rate of deformations from radar data using the SBAS algorithm compared to the leveling data has followed a similar pattern. However, there may be some error due to the different nature, ie in the leveling of elevation deformations measured for a point, but in interferometry the average rate is obtained from adjacent points.

In recent years, the irreversible phenomenon of land subsidence has led to environmental hazards in various plains of Iran including Gorgan. In general, the most important activities causing this phenomenon are inappropriate groundwater withdrawal and geological factors. The research method consists of two sections: identifying subsidence areas and examining the effective factors and parameters and evaluating the impact of each. In identification section, radar interferometry technique was used to compare the phase taken from two radar sets from the same region at two different times and measurement of land surface changes over time can be achieved through interferogram, and in the effective factors analyzing section, the determination and analysis of effective parameters such as water level drop, texture and thickness of soil layers, especially fine-grained layers were investigated. The results of the satellite data analysis indicate that the region is steadily subsiding. The mean velocity map along the satellite line of sight obtained from time series analysis showed a subsidence rate of 14 mm / month (169 mm / year). The identified subsidence range is approximately eastern-western which is consistent with trends in structures such as the Caspian. Figures of water level and precipitation in this area during 2007 to 2009 show a decreasing trend despite of seasonal fluctuations, and analysis of effective parameters shows that the subsidence is due to the same drop in water level or the difference of same thickness of the fine-grained layer at different depths

Soil erosion is a phenomenon that is carried out by the wear and tear of soil on the surface of the earth and its transfer to another place by water or wind processes. This process has caused the emergence of many geomorphological forms and landforms in the world (Shayan and Zare, 2011). The extent of the world's reservoirs is large and these areas have active dynamics due to the instability of sands and undergo many geomorphological changes in a short period of time. There are many wind landforms of compression and erosion type in Lut desert. These geomorphological and geological phenomena are one of the most important natural attractions of the Lut plain and desert, which can be said to be rare or unique in the world. Landforms such as huge sand dunes and pyramids, which are unique in their kind in the world, have a very high ability to attract different tourists, including adventure tourists, scientific tourists, educational tourists, and other tourists (Maqsoudi et al. 2004). In this research, the Dayvis erosion cycle has been investigated in the Lut desert geoforms using differential radar interferometric techniques and the collection and deposition points have been revealed.

In order to reveal the harvesting, transportation and sedimentation areas of the Lut desert world heritage, the radar data of Sentinel 1 satellite and the digital model at a height of 30 meters have been used for software processing. The radar technology that has been provided thanks to the rapid development of space technology (Ferretti et al., 2007) has been done with the radar interferometric method (DInSAR). In this research, we also used Landsat 8 satellite images to prepare a map of the study area, ASTER satellite digital elevation model (DEM) with a resolution of 30 meters to prepare a hypsometric map and radar processing, vector layers of geoscience databases, and windfalls of synoptic stations located around the study area. It has wind direction and speed information; it is also prepared from the National Meteorological Organization. Information processing has also been done in SNAP and GIS software.

In order to reveal the harvesting, transportation and sedimentation areas of the Lut desert world heritage area, the differential radar interferometry method was used between 2019 and 2020 and the radar data of the Sentinel 1 satellite, which is of C-Band type and has the penetration of radar waves with a wavelength equal to the frequency of 405 5 GHz is used. According to the outputs, the phase difference between the two data in the Kluts has a negative trend and it is quite noticeable that it shows the erosibility of the Kluts, which is caused by the winds of the region.It should be noted that due to the resistance of Lut block to the internal forces of the earth, the effect of faults in the height changes in the bedrock of Lut block and the area of the Kluts is very small and the observed changes are only due to wind erosion. After the unwrapping process, the unwrapped layer is converted into a displacement layer and then georeferenced. The final map of the vertical displacement of Lute Kluts was drawn in a general and classified manner, which shows many changes during a year. But in general, the northern parts of Klut have more erosion resistance due to high wind speed and high erosion power. The yardangs in the northwest parts of Kluts can be a proof of this statement. Therefore, most of the area of Klots is eroding every year and these sediments have been accumulated in many parts of Rig Yalan. Middle Hamada can be considered as a transition range. In order to investigate the dominant processes in the creation of geomorphological complications in Lut, synoptic data were analyzed at Shahdad, Nehbandan and Nusratabad stations, and the gulbads of the region were drawn. According to the winds of the region, the erosion trend of the Klots from the northwest to the southeast shows a significant trend in wind erosion.

Since Lot is the most important natural work of the country that has been registered globally, investigating its geomorphological complications is also one of the research priorities. These surveys allow for accurate knowledge and information about the conditions and characteristics of the region. Among these, Kluts and Rig Yalan are the most important geomorphological phenomena of Lot, which were investigated in this research. Kluts and Rig Yalan are located in the hydro-eolian region and are always subject to significant geomorphological changes. According to the investigations carried out in this research, it was found that there is an erosion cycle in the area of Klut. Rig Yalan and Middle Hamada. In the area of Kluts, the highest amount of digging was observed in the northern and central parts. In the northern part of the Middle Hamada, which was referred to as the transfer zone, it shows the digging of sediments, but in the southern parts of this region, we have sediment accumulation. In different parts of Lut sand, which is known as the sedimentation area, the accumulation of sediments has been different, so that in the western and western parts, the height of the sand pyramids has decreased, but in the eastern and especially the northern parts. The east shows the increase in height and accumulation of sediments. According to the mentioned contents, the erosion cycle in this range is rotational and in the counterclockwise direction. Among the articles that have been worked in Lut and can be cited as a confirmation of this research, is the article Thermal cyclone of Lut, Yemen, in which he mentions the existence of a thermal cyclone in Lut and the air flow in this cyclone is opposite. The hands of the clock say.

Various natural phenomena have had a significant impact on the quality of human life since long ago. One of these types of natural phenomena is the deformation and displacement of the earth's surface, including subsidence. Subsidence is a morphological phenomenon that occurs under the influence of the downward movement of the earth. The salient features of radar images and the acceptable accuracy of the radar interferometric method have provided a powerful tool for researchers in investigating land subsidence. For this reason, 35 radar images of the Sentinel 1 sensor in the ascending orbit and transit 174 in the period from 2016 (June) to 2021 (January) were used to investigate the land subsidence in the Kermanshah plain. To analyze the time series of these images to prepare the average annual subsidence map in the plain, the radar interferometric technique was used under PSI and SBAS approaches. The results show the maximum land subsidence of 100 mm in the SBAS method and 10 mm in the PSI method in the west and northwest of the plain for 6 years. Finally, the maximum range was investigated in terms of geology and geo-hydrology. The results of the investigations showed that the land use of the maximum land subsidence area includes irrigated and rainfed agricultural lands, with the highest amount of water withdrawal in the agricultural sector, along with an average drop in the water level of 8 meters in 20 years in wells with a large thickness of fine-grained sediments. Is. In general, land subsidence in the area is affected by human and natural factors

Land subsidence is one of the environmental hazards caused by various factors, and especially in recent years, it has caused a lot of damage to human societies. The Khanmirza plain aquifer has also faced this phenomenon in recent years. The creation of wide gaps and cracks on the surface of the plain and the release of gas from them makes the issue of subsidence important. For this reason, the present study tries to monitor and measure the amount of land subsidence in Khanmirza plain, and evaluate and analyze its relationship with the withdrawal of excess from underground water sources. For this purpose, in order to investigate the changes in the underground water level during 10 years and in two different time frames from the IDW geostatistics model and to estimate the subsidence of the land surface using the differential radar interferometric method and from the Sentinel-1A radar images during 5 years and in Three different time periods were used. The results of the research indicate that displacement of the earth's surface in different time periods is different and does not have a constant trend, while the trend of the drop of the underground water level has been increasing in the whole time period. Accordingly, according to the results of the research, there is no significant relationship between the indiscriminate extraction of underground water sources and the subsidence areas in Khanmirza plain.

Land subsidence induced by soil consolidation is one of the natural hazards that occur gradually. This phenomenon has reached its critical state in most regions of Iran. Factors affecting subsidence are groundwater level depletion, land cover, soil type, elevation, slops gradient, rock bed depth, etc. The causes of subsidence should be investigated so that decisions could be based on the real characteristics of the region. Decrease in groundwater level is one of the most important factors that influences subsidence but due to the complexity of the relationship between subsidence and other factors, a direct linear relationship between groundwater level and subsidence cannot be considered. The study aimed to investigate the relationship between subsidence and groundwater changes through relationship between the two parameters in the period 2014 to 2018 in Isfahan. In this regard, the time series of radar interferometry and the time series of water levels of piezometric wells in the Isfahan were studied. The results show that in 12% of the wells, no correlation exists, in 9%, poor positive ignorable correlation, in 12%, fair positive correlation, in 48%, significant positive correlation, in 6%, poor negative ignorable correlation, in 4% fair negative correlation and in 9% there is a strong and negative significant correlation between the subsidence rate and the groundwater level. Correlation values show the complexity of the relationship between subsidence and water level depletion. Therefore, the relationship between subsidence and its causative factors requires more detailed studies and comprehensive models.

River terraces represent a history of river stratigraphy and provide valuable information for understanding the interactions of tectonics, erosion, and climate change. The high altitude of the Jajrood basin has resulted in extensive glacial remnants, especially the accumulation of moraines upstream of the basin. The extent of moraine depositions under the upstream basins of the Jajrood River is not evident in the structure of river terraces and they do not have a uniform elevation. Moreover, the relations of old glacial conditions in the sedimentary interference of terraces cannot be easily reconstructed and discriminated, and there is no regular order in the stratigraphic sequence and sedimentological conditions of the river terraces. The moraine deposition seemingly has had a major role in the differences in river terrace sequences from upstream to downstream of the study area, which calls for further investigation and is also addressed in this study. Many studies have delved into the analysis of the evolution of the river terraces. Other important areas of study include paleontology and sedimentology and their effects on the canal sustainability against flow dynamics. This study aimed to explore the climatic and neo-tectonic developments of the Jajrood River Basin and the role they have played in creating terrace sequences.

This pure research investigated the role of neo-tectonic developments and climate change on the formation and evolution of terraces in the Jajrood River Basin. The research was based on analytical calculations and reports prepared through surveys as well as remote sensing methods to examine the effects of tectonics in the area. In addition, sedimentological evidence was studied to see how climate change has affected the formation and evolution of these terraces. The primary research tools were topographic and geological maps alongside aerial photographs and satellite images. Other fieldworks such as terrace morphometry using GPS measurements and sedimentological analysis helped to add insight to the findings. Then, the data was analyzed in ArcGIS. Here, the Jajrood Canyon was divided into three sections to better examine the morphogenesis of the terraces. Next, the transverse profiles and stratigraphic sections were drawn up to investigate the sedimentary strata in each section through morphometry, and then the evolution of the terraces was analyzed and reconstructed. The tectonics were studied using radar images to determine vertical displacement through the small baseline subset (SBAS) time series. Here, 27 Sentinel-1 images were used for the period from Oct. 14, 2014, to Oct. 27, 2016. which was performed using Generic Mapping Tools (GMT) in Linux OS. After preparing the interferogram maps, a map of the displacement in the study area was generated using the SBAS method (Zhao, 2013). Moreover, changes in the climate were studied using sedimentological and stratigraphic evidence.

The research findings can be classified into two parts. First, neo-tectonics was investigated through remote sensing methods and the analysis of vertical displacement across the region. Then, the effects of these neo-tectonic processes on the genesis and evolution of terraces were examined. In the second part, the effect of climate change on terrace developments was explored using sedimentological and stratigraphic evidence. In the first part, the region's tectonics was analyzed using radar imagery. In doing so, the vertical displacement was measured using SBAS time series and 27 Sentinel-1 imagery during the period from Oct. 14, 2014, to Oct. 27, 2016. The specifications of the research images are presented in Table 1. The images were selected based on the research purpose and the baseline of the images relative to each other. The VV polarization was used for all images since co-polarizations exhibit a stronger backscatter. Some sensors have different polarizations, and images with different polarizations can inform interpretations to a great extent.After preparing the images, for measuring displacement using the SBAS method, first, the temporal and spatial baseline of the images was examined and image pairs were selected for interferogram generation (Table 2 and Figure 3), which was performed using GenericMapping Tools (GMT) in Linux OS. After preparing the interferogram maps, a map of the displacement in the study area was generated using the SBAS method. In the end, the role of morphotectonic relations in the morphogenesis (i.e., origin and development) of the terraces were examined.

These findings suggest that terraces in the Jajrood Canyon are highly heterogeneous in terms of sedimentological structures, stratigraphy, and altitude. For instance, the T3 to T1 terraces, respectively, were located 130, 90, and 80 m above the river. These terraces have also experienced three intermittent processes. These three river terraces were created through the combined effects of climate change, tectonic uplifts, and the formation of dam lakes. The results of SAR interferometry (InSAR) and fieldworks also confirm the effect of active tectonic uplift differences along the main canal. These differences reflect the differences in their morphogenetic processes. The altitude of the terraces at the Oushan River tributary (Section 1) is nearly 130 meters. However, this section's altitude downstream (near Hajiabad Village) is estimated at 90 m. This difference cannot be merely due to baseline discrepancies. Evidence indicates that a sedimentary interference originating in the lake due to a past landslide downstream of the study area (Hajiabad landslide) is the cause of the higher altitude of the terraces in this section. The terrace sequences were not the same in any of the three sections. To be more precise, there are three identifiable terrace levels in Section 1, two in Section 2, and one in Section 3. In addition to the differences in the tectonic baseline, three factors—namely climate change, moraine, and the formation of a landslide-dam lake downstream—were identified for the genetic diversity, sequence differences, and terrace sequences throughout the three sections. In addition to morphometric differences, there were great differences in the genesis of the terrace sediments. The river has contributed the most to the formation and structure of terraces and their genesis. Nevertheless, the interference of landslide-dam lake deposits, moraines, and alluvial deposits, consecutively or simultaneously, have affected particularly sections 1 and 2 through differences in flow dynamics. Meanwhile, greater uniformity can be seen upstream, particularly in the Garmābdar basin (Section 3), such that upstream terraces in this section are predominantly glacial.

 Landslides are one of the most complex and at the same time harmful phenomena, as a result of which the slope material is moved from the sloping surfaces and relatively deep wounds are left on the surface of the slopes. A phenomenon near cultural features, such as residential areas, roads, etc., causes financial damage and many casualties. The use of geographic information systems in the first place, followed by the use of satellite image analysis technology, is of great help to this part of management. For this purpose, the D-InSAR radar interferometry technique, with its frequent, continuous wide ground coverage and high temporal and spatial resolution, as one of the most accurate and least expensive remote sensing techniques, to display the displacements that occur in the ground surface is provided. The present study investigated the existence of landslides in the study area of Sarbaz village by means of Sentinel 1 sensor radar images and using radar interferometric technique in the period of 2017 and 2018. After various processes that were done in ENVI software and SarScape plugin, the amount of displacement and landslide of the area was obtained, and according to the results obtained, it can be said that Sarbaz area is an area with a high level of activity in terms of landslides. Also, 3 points have been introduced as points with high sensitivity, which were found to be in the medium to high risk level. The obtained results showed that Sarbaz region had a displacement of -0.069 in the period of 06/05/2017 to 12/14/2017, in fact it had a displacement of nearly 7 cm, in the period of 12/14/2017 to 12 In 06/2018, the amount of displacement was -0.035, which means that nearly 4 centimeters of displacement occurred in the region, and between 12/06/2018 and 21/12/2018, the displacement in the region was equal to -0.064, which It shows that there has been 6 cm displacement in the studied area during this time period. At the end, a map of sensitive points was prepared and presented.Deformation of the soil surface is a dynamic process on the Earth's surface, this process occurs naturally or due to human intervention. One of the forms of this deformation is landslide [7]. The definition of landslide is the general and deep movements of the entire soil layer on the surface of the mother earth, which cause heavy damages every year, sometimes it is not possible to compensate for these damages, and we need to spend a lot of time and money. The speed of their operation and their extent often creates spectacular and sometimes catastrophic phenomena, and they may affect tens or hundreds of thousands of cubic meters of rock and soil in one place. This phenomenon works mostly in isolated sediments [10]. The effects of domain instability are mass movements on a small to large scale. Range movements may be minor and unique to the fall of a single piece of rock, or they may be very large and catastrophic. The damage caused by this type of movement is more in developed countries, but 95% of the deaths caused by it happen in developing countries. Landslides are among the most devastating natural disasters in steep areas, the damage to residential areas and economic infrastructure, as well as human casualties caused by landslides are increasing worldwide [9]. Iran, with its mainly mountainous topography, tectonic activity and high seismicity, diverse geological and climatic conditions, has the main natural conditions for creating a wide range of landslides [4]. By using morphotectonic indicators, it is possible to help planners by providing maps in predicting the places that will become unstable due to future earthquakes. By using morphometric analysis and using geomorphic indices and rank parameters of drainage networks, the active tectonics of a region can be investigated [5]. Among the presented methods, we can mention tachometry, leveling, short-range photogrammetry, observations from geodetic networks [GPS], radar interferometry, and lidar. Although the first use of radar data in investigating the instability of the earth dates back to the mid-1990s, in recent decades, due to the availability of radar data with a long time span compared to the past, and the development and expansion of new methods such as techniques Interferometry has drawn the attention of researchers to the use of these methods [4]. Among the remote sensing techniques, differential radar interferometry [DINSAR], which has the ability to work in all bad weather conditions and the length of day and night, is considered as one of the effective and efficient techniques in monitoring slow changes in the earth's surface [11]. Due to the fact that natural phenomena and hazards will cause damage in different regions, therefore, it is important and necessary to investigate these issues in different time frames and regions in the country. This research was conducted for the first time in the studied region. and the purpose of doing it is to investigate the amount of landslides in Sarbaz village in Isfahan province using radar satellite images, remote sensing techniques and radar interferometry. Therefore, this research is innovative in terms of being new and up-to-date.

 In the current research, in order to monitor and determine the amount of displacement caused by the movement of the sliding mass of Sarbaz village, the radar interferometric method and Sentinle-1, radar satellite images with C-band wavelength in the ascending orbit mode have been used. Radar interferometry or interferometry is the method of using the phase difference of signals returned from the earth's surface in two SAR images taken with a time delay or with parallax from a region to extract height or information related to changes in the earth's surface. In order to implement the DInSAR method, one should first pay attention to two principles between each pair of radar images (main image and secondary image), the first is the temporal baseline and the second is the spatial baseline. After choosing suitable interferometer pairs based on temporal and spatial baselines, in the next step of processing these images, and in order to remove the topography effect from the interferometer, the method of preparing the interferometer along with the digital height model was used. The output of this stage of the work is in the form of a differential interferogram in the form of a flattened interferogram in which the stationary phase and the topographic phase are removed from the interferogram. Since the flattened interferometer contains noise that lowers the visual quality of the fringes, the adaptive filter is used for this purpose.

Identifying areas prone to landslides and zoning the potential of landslides is very necessary and important in order to avoid these areas and implement prevention and control methods. In order to implement the DINSAR method in this research, the capabilities and quality of the radar images used to prepare the interferometer were checked by calculating their temporal and spatial baseline values. Table 1. The results of numerical processing of landslides and accumulation of sediments The amount of displacement in these maps is shown in the form of a numerical range between negative values and positive values in meters(Figure 2). The level of the range and slopes and positive values indicate the accumulation of sediments at the foot of the range and slopes. According to the maps of phase transformation to displacement of the landslide and the analysis of images in different time intervals, the metamorphosis of the landslide surface can also be explained well. Figure1. General map of landslides and accumulation of sediments According to the results obtained and determining the amount of landslides in the region, we have reached a positive correlation with the results of similar works, according to the results of similar works in the field of landslides that Sadeghi et al. (2022), Casagli et al. (2016), Hammand et al.(2019), Deming et al.(2020), it is concluded that by using remote sensing and radar interferometric technique, the amount of landslides in different areas can be determined with high accuracy and low cost. achieved and provided the results to relevant authorities to provide appropriate solutions.

In the new decade, the use of new technologies in the field of urban management as well as natural disaster management has had a growing trend. The use of geographic information systems in the first place, followed by the use of satellite image analysis technology, is of great help to this part of management. The present study calculated amount of landslides in Sarbaz village in Semiram city of Isfahan province by using Sentinel 1 radar satellite data and with radar interferometric technique. It is caused by landslides or, on a smaller scale, human activities. Negative numbers and sections indicate falls on slopes and other areas.  According to the obtained results, it can be said that Sarzab region is an area with a high level of landslide activity. Also, 3 points have been introduced as high sensitivity points, which were found to be in the medium to high risk level. The obtained results showed that Sarbaz region had a displacement of -0.069 in the period of 06/05/2017 to 12/14/2017, in fact it had a displacement of nearly 7 cm, in the period of 12/14/2017 to 12 In 06/2018, the amount of displacement was -0.035, which means that nearly 4 centimeters of displacement occurred in the region, and between 12/06/2018 and 21/12/2018, the displacement in the region was equal to -0.064, which It shows that there has been 6 cm displacement in the studied area during this time period.

Land subsidence is commonly referred to as vertical downward movements of the earth's surface that can be accompanied by a slight horizontal vector. Land subsidence is a global problem and a morphological phenomenon. This phenomenon is affected by human activities and natural factors that may become a threat to humans and human achievements. The phenomenon of subsidence, although imperceptible and gradual, but is associated with many risks, including the creation of potholes, failure and cracking of buildings, skewing of high facilities, damage to agricultural facilities, breakage and destruction of stairs Roads and network of urban thoroughfares. Therefore, this issue affects the urban areas more, which if not addressed can lead to many human and financial losses. Accordingly, monitoring the rate of land subsidence in order to reduce the negative effects as well as controlling its development process, will be very important and it is necessary to regularly estimate the area subsidence trend. Due to the importance of the issue, in recent years, various studies have been conducted in the field of subsidence and advances in the field of remote sensing have led to monitoring the phenomenon of subsidence, unlike in the past, with greater accuracy and speed. One of the methods that has received a lot of attention in recent years is the radar interference method, which has high accuracy and speed in processing information and monitoring land surface changes, so in this study, this method is used to monitor the situation. Subsidence of cities located in Hamedan-Bahar plain has been used.

In this study, in accordance with the intended objectives of Sentinel 1 radar images (73 radar images during the period 16/01/2015 to 14/01/20120), the information of piezometric wells in the region (related to the Water and Regional Organization of Hamadan Province ) And the 30 m SRTM digital elevation model have been used as research data. Important research tools also include GMT (for radar interference measurement and SBAS time series) and ARCGIS (for mapping). This research has been done in 2 general stages. In the first stage, the amount of subsidence in the area is assessed using radar images. In order to perform this step, radar interferometry and SBAS time series method have been used. In the second stage, the annual drop in groundwater in the region is evaluated. At this stage, in order to assess the annual drop in groundwater in the region, information about 25 piezometric wells located in the study area in the period of 1375 to 1395 has been used.

The study of subsidence results in the study cities indicates that the average annual subsidence in the urban area of Hamedan was about 23 mm, the highest amount of which was related to the western regions of the city. The average annual subsidence in the urban area of Bahar was about 9 mm, the highest rate of subsidence was in the southern areas of the urban area. The average annual subsidence in the urban area of Salehabad with 6 mm was lower than other cities, but the average annual subsidence of Lalejin with 47 mm was the highest among cities. Also, in this research, information related to 25 piezometric wells (statistical periods of wells related to the years 1375 to 1695) located in the study area has been used. Examination of the level of water level drop in the studied wells indicates that these wells have faced a lot of water level drop, so the average annual drop of wells is calculated between 100 to 2070 mm. The study of the spatial status of groundwater depletion indicates that the middle areas of the study area have the highest average annual groundwater level depletion.

The results obtained from the assessment of subsidence in the studied urban areas indicate that the highest amount of subsidence occurred in the urban area of Lalejin, so that this area during a period of 5 years (01/16/2015 to 01/14 / 2020) had a subsidence between 26 and 234 mm (average annual 47 mm). In this study, the situation of groundwater resources decline has also been evaluated. The results show that the average annual drop of wells in the region is between 100 to 2070 mm, which is the highest rate of decline in the middle areas of the study area, and given that in this region, the highest rate of subsidence also occurred. Given that there is a significant relationship between land subsidence and groundwater level decline (correlation 0.7). In fact, a study of the subsidence of cities in relation to the decline of groundwater resources indicates that the city of Lalejin, due to its location in the middle of the area and the high annual rate of groundwater decline, had the highest rate of subsidence. Also, the results of evaluations have shown that in addition to the decrease of groundwater resources, constructions have also played a role in increasing the rate of subsidence, so that the city of Hamedan has faced less groundwater loss than the city of Bahar, but it had more subsidence. Considering that the highest rate of subsidence occurred in the western, southern and eastern regions of Hamedan urban area and these areas have faced a lot of physical development in recent years, so it can be said that in addition to water loss Underground, the development of construction has also played an important role in the rate of subsidence in this city.

Estimation of subsidence rate using radar interferometry technique and groundwater parameters and land use (Case study: Ardabil plain)IntroductionThe phenomenon of subsidence has affected many parts of the world, including Iran, and in recent years has been raised as one of the main issues and challenges. This phenomenon has developed in different regions under the influence of different factors. In Iranian subsidence, groundwater loss has been suggested as the main factor. Because there is a direct relationship between subsidence of areas and the rate of groundwater loss in different areas. In fact, the prevailing dry climate in most parts of Iran and the concentration of industrial, agricultural and drinking water consumption on groundwater resources, has provided a good infrastructure for the occurrence of this phenomenon. Due to the importance of the issue in recent years, various studies have been conducted in the field of subsidence and advances in the field of remote sensing have led to monitoring the phenomenon of subsidence with greater accuracy and speed than in the past. . Which has received a lot of attention in recent years Radar interference method that has high accuracy and speed in processing information and monitoring land surface changes. Therefore, in this study, this method has been used to monitor the subsidence of Ardabil plain.MethodologyIn this study, First, radar interferometry method has been used to investigate and measure the amount of subsidence. One of the powerful tools for monitoring the subsidence phenomenon is the radar interferometry method. This method is able to determine the changes in the earth's surface in that time period by comparing the phases of two radar images taken from an area at two different times. Sentinel 1 satellite images from 2016 and 2020 were used for this purpose. Considering the direct effect of groundwater decline and increasing its utilization rate on subsidence, in the present study, the status of piezometric wells in the Ardabil plain was evaluated by intriguing method (kriging). Kriging interpolation requires zero mean estimation error. Absolute estimation in interpolation is one of the main features of Kriging model. Also, This means that the estimated value of the quantity at the sampling points is equal to the measured value and the variance of the estimate is zero. Object-oriented method was used to classify the images in the land use map in this study. This is because the method uses information from other pixels (size, shape, texture, etc.) for classification in addition to spectral information. Image objects are created based on parameters such as scale, object shape, color, compression ratio that are determined during interpretation.ResultsThe study of subsidence according to Figure 3 in the last 5 years from 2016 to 2020 in the study area shows that the amount of subsidence is 4 mm per year and 22 mm during 5 years. In order to reconcile the results of radar interferometry with other supplementary data, land use map as well as piezometric wells in Ardabil plain were used. By reviewing and analyzing the land use map and subsidence of Ardabil and field studies confirm the maximum occurrence of subsidence in agricultural areas and good rangelands or 0.22 mm, medium rangelands 0.21 mm and 0.20 mm It provides unsafe and risky living conditions for the residents of Ardabil plain and indirectly has reduced the quality of environmental conditions and life of the residents of Ardabil plain. Land subsidence is a pervasive phenomenon in the world, which has had a significant quantitative and qualitative manifestation in recent years, mainly due to the improper exploitation of groundwater resources and the intensification of its surface decline. To investigate the situation and the effect of groundwater level decline and its effect on the subsidence of Ardabil plain from the information of 39 piezometric wells (obtained from Ardabil Regional Water Organization) during the years 1987 to 2020 that the results of the analysis of a decrease of 48% Shows the water level in 2020 compared to 1987. The maximum water level of piezometric wells has increased from 45 meters to more than 70 meters in 2020, which indicates the deterioration of the Ardabil plain aquifer. Which requires the identification of effective factors, mitigation measures and adaptation measures, including the restriction or prohibition of groundwater extraction in areas subject to subsidence and the implementation of strict regulations for extractors of groundwater resources in areas subject to subsidence and continuous monitoring Indicators of subsidence.ConclusionsIn this study, the extent and distribution of subsidence in Ardabil plain and the effect of groundwater level decline and land use on land subsidence were investigated by radar interferometry, interpolation and object-oriented methods. Studies show subsidence of 22 mm over a period of 5 years. The results of data analysis of 39 piezometric wells in Ardabil plain in a period of 33 years show an average groundwater drop of about 9.5 meters. Co-institutionalization of subsidence maps with land use layers also confirms the maximum occurrence of the settlement area, which has the highest rate related to good pastures and agricultural areas0 / 22. Mm, medium rangelands 0/21 mm and man-made areas0 /20 mm.

Landslide is a geological phenomenon that includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. Landslides are caused by various natural and human causes. Due to its damages, landslide activities must be considered in various construction, industry and agricultural activities. There are several methods for measuring the motion of the earth's crust caused by landslides. These include microgeodesic methods using accurate leveling and GPS observations. It will not be possible to repeat these measurements with this methods due to the high cost and difficulty. Therefore, it is not possible to provide timely and widly information on movements and displacements caused by landslides.SAR interferometry technique is one of the newest remote sensing techniques that by processing radar images has provided the possibility of preparing earth crust movement maps on a large and continuous surface.

One of the principal applications of the SAR technology is represented by the SAR interferometry (InSAR) technique. SAR interferometric techniques combine complex images recorded by antennas at different locations or at different tima to form interferograms which permit the determination of minute differences in the range (distance) to corresponding points of an image pair, on the sub-wavelength scale. By combining three radar images as two pairs of interferograms were able to separate topographic and dynamic effects and thus estimate the coseismic displacement field using radar data alone. The purpose of this study is to evaluate the capability and capability of radar interferometry technique in landslide detection. Radar interferometry processes and the results are presented in order to identify landslides in the study area (Koohrang county). Radar images taken by ASAR (Advanced SAR) sensor, which is one of the ENVISAT satellite sensors, are used for radar interferometry processing and interferogram creation.

Seven interferograms were formed on all pairs of available images. In three cases, fringes indicating landslides were observed. Considering the elimination of the topographic effect in the above interferograms and considering the fact that no earthquake has been recorded in this area during this period, so the fringes formed in this interferograms can be related to the occurrence of landslides. Considering the consistency of the observations of all three interrograms, the approximate average displacement rate has been calculated for each of these landslides.Among the identified sites as landslides, only two cases are located in Chaharmahal and Bakhtiari province. One of them is located in the vicinity of Kofi village and another one is detected in Dehdeli village in Ardal county.

The approximate maximum ground displacement of landslides detected in the range of radar sensor visibility was estimated in centimeters. Extensive coverage of radar images in InSAR technique is one of the important advantages of this technique. Therefore, using this technique, make it is possible to identify active landslides, even in Inaccessible areas. Due to the presence of images in the archives of radar satellites such as ENVISAT satellites, it is possible to monitor landslides over the past years to the present.One of the limitations in using the SAR interferometry technique is that all SAR images taken are not suitable for forming interferrogram. In fact, reducing the correlation of images such as Baseline Decorrelation and temporal decorrelation are important obstacles in using this technique in different situations.Another limitation factor of this technique that can be considered is low spatial resolution of the resulting interrograms. This in turn causes the loss of small displacement ranges, in other words small landslides.Accurate Global navigation satellite system point observations can be used as a complement to InSAR observations (continuously and extensively) in landslide modeling.The following suggestions for using this technique in the study of landslides are presented.A) Since it is possible to identify landslides and calculate the displacement vector for high-precision radar sensor vision using InSAR technique, use this technique to identify and monitor active landslides in order to complete the land database. Slips are suggested.B) Conducting research to extract the dimensions and components of a landslide (including parameters such as canopy, peak, landslide, displaced mass, depletion zone, accumulation zone, etc.) from the results of InSAR technique to model landslide seems necessary It arrives.C) GPS point and sight observations can be used as a complement to InSAR observations (continuously and on a large scale) in landslide modeling.D) Due to the low spatial resolution of the displacement interrogram resulting from the use of the digital SRTM elevation model with a pixel size of 90 m, conduct research to use digital elevation models with better pixel size to reconstruct the topographic phase and finally obtain An interrogram requires better displacement with better spatial resolution. Undoubtedly, in such an interrogram, the probability of identifying landslides that have occurred in small areas will increase. 

Introduction:

 The phenomenon of land subsidence involves collapse or sinking of the earth's surface, which can also have a slight horizontal displacement vector. This movement is not limited in terms of intensity, extent, and measure of the involved areas. Subsidence in cities leads to costly and serious damage to urban infrastructure such as buildings, roads and railway tracks. Land subsidence can occur for a variety of reasons: groundwater abstraction, Subsidence due to oil extraction in oil fields, Displacement due to landslides and collapse of internal walls of mines.Numerous techniques and methods have been implemented to study the extent, action and land expansion and behavioral measurement in relation to land subsidence. One of the most recent and the most effective methods is the radar image interference technique. Interferometric Synthetic Aperture Radar (InSAR) is a powerful technique for measuring the topography of a surface and its changes over time. Due to its broad spatial coverage and high accuracy, InSAR has become a preferred geodetic method for the study of land deformation in developed groundwater basins and provides insight into the geological and hydrological parameters that characterize the underlying aquifer systems.Varamin plain is one of the areas affected by subsidence in Iran, which is located in the alluvial fan of Jajrud river and its development and prosperity is due to the quality and fertility of the soil in this region. Irregular and over pumping of groundwater has caused many subsidence cases in the study area. This study investigates the subsidence of Jajrud alluvial fan with emphasis on Javadabad Varamin from 2016 to 2019, using permanent scatter radar interferometry method.

Materials and Methods:

 In this study, 41 images of Sentinel (2016-2019) were used to determine the rate and amplitude of land subsidence using the method of permanent dispersants. Permanent scattering points (PS) were selected based on the domain scattering index. The amplitude scattering index, according to the threshold limit is usually considered to be 0.4 or 0.42 in various studies, which means that all selected points are not located in the set of PS points and only those points to be selected that the amplitude scattering index value is exceeding the threshold. Then, at this stage, points network (PS) was prepared in order to evaluate the processing performed. The prepared spatial network in this section is derived from the Delaunay model. Due to this fact that the amount of displacement is relative in this method, therefore, one of the points in the area is selected where the amount of displacement is relatively zero in compare to other points and other PS points are applied to it. Because of seasonal temperature changes and its effect on buildings that cause elevation changes (the effect of temperature on the structure of buildings), selected point must be located on the ground. SNAP software was selected for radar interferometry processing.. In order to find the cause of subsidence, the information of piezometric wells (1996-2016) in the study area and its temporal changes were investigated.

Results and discussion:

 research findings یافته های پژوهش:The findings یافته ها:Can't load full results Try again Retrying… Retrying… Can't load full results Try again Retrying… Retrying… In general, land subsidence has occurred in two large areas. The northern region is located in the Jajrud alluvial fan. The length of this zone is 44 km and its width is 7 km, which covers an area more than 300 square kilometers. In general, we have land subsidence in two broad areas. به طور کلی ، در دو منطقه وسیع فرونشست زمین داریم. In general, the vast expanse of land subsidence have occurred. به طور کلی ، پهنه وسیع فرونشست زمین رخ داده است. Can't load full results Try again Retrying… Retrying… Its northern region is located in the Jajrud alluvial fan. منطقه شمالی آن در مخروط افکنه جاجرود واقع شده است. North Zone is located in the fan MkhrvtAfknh Jajrood. منطقه شمال در فن MkhrvtAfknh Jajrood واقع شده است. Can't load full results Try again Retrying… Retrying… The length of this zone is 44 km and its width is 7 km, which covers an area of 300 square kilometers. طول این منطقه 44 کیلومتر و عرض آن 7 کیلومتر است که مساحت آن 300 کیلومتر مربع است. Over the span of 44 km and a width of 7 meters, which is the area of over 300 square kilometers in the lie. بیش از 44 کیلومتر و عرض 7 متر ، که مساحت بیش از 300 کیلومتر مربع در دروغ است. Can't load full results Try again Retrying… Retrying… The highest amount of subsidence in this area is related to Golabbas area, which is about 120 mm per year. The presence of Jajrud alluvial fan and agricultural lands in this area is considerable.The second region is related to the southern zone. The northern part of this zone is bounded by the city of Pishva, Qala-e-Sin and the east of Varamin city. In these areas, the annual subsidence rate reaches to maximum 6 cm. The southern part of this zone is surrounded by Hesargol and Jahanabad areas. The second area is related to the southern zone. The northern part of this zone is limited to the city of Pishva, Qala-e-Sin and the east of Varamin city. منطقه دوم مربوط به منطقه جنوبی است. قسمت شمالی این منطقه محدود به شهر پیشوا ، قلعه سین و شرق شهرستان ورامین است. The second extension of the South zone is an area in the north of the city limits Rector, Xinjiang and East fort city of Varamin is limited. گسترش دوم منطقه جنوبی منطقه ای در شمال محدوده شهر رکتور ، سین کیانگ و شهر قلعه شرقی ورامین محدود است. Can't load full results Try again Retrying… Retrying… In these areas, the annual subsidence rate reaches a maximum of 6 cm. در این مناطق ، میزان فرونشست سالانه به حداکثر 6 سانتی متر می رسد. In these areas the annual subsidence reaches up to 6 cm. در این مناطق فرونشست سالانه تا 6 سانتی متر می رسد. Can't load full results Try again Retrying… Retrying… The southern part of this zone is limited to Hesargol and Jahanabad areas. قسمت جنوبی این منطقه به مناطق حصارگل و جهان آباد محدود می شود. The southern part of the zone in MntqhHay hesar goli and JhanBad is limited. قسمت جنوبی منطقه در MntqhHay hesar goli و JhanBad محدود است. Can't load full results Try again Retrying… Retrying… In these areas, the rate of land subsidence is lower compare to the central areas and it is about 20 to 40 millimeter per year. In the northern part of Jahanabad region, the maximum land subsidence is 60 mm per year. The southern zone in which the study area is located has circular shape and the amount of land subsidence increases from the periphery to the center of the region. The highest rate of land subsidence in the study area is occurred in Salman-Abad, Khaveh, Javadabad, Hesar-e-Sorkh and Zavarehvar areas, with the amount of between 160 to 200 mm per year. Areas such as Tajreh, Rostamabad and Hesar Kouchak also show significant land subsidence, that is about 120 to 160 mm per year.The result of radar interferometry studies has demonstrated that subsidence has occurred in the main parts of the Jajrud alluvial fan's surface. Javadabad region which is located in Varamin is one of the areas with significant subsidence that subsidence occurs at a rate of 20 cm per year - Javadabad region of Varamin is one of the areas with significant subsidence that occurs at a rate of 20 cm per year of land subsidence. - منطقه جوادآباد ورامین یکی از مناطقی با فرونشست قابل توجه است که با سرعت 20 سانتی متر در سال از فرونشست زمین رخ می دهد. - Regional Branch of MhdvdhHay JvadBad with significant subsidence zone at a rate of 20 cm annual event that there is land subsidence. - شعبه منطقه ای MhdvdhHay JvadBad با منطقه فرونشست قابل توجه با نرخ سالانه 20 سانتی متر که فرونشست زمین وجود دارد. Can't load full results Try again Retrying… Retrying… Studies conducted in the study area depicted that the decreases in groundwater level in the study area is linear and this is acceptable in justifying land subsidence. Studies conducted from the study area showed that the drop in groundwater level in the area is linear and this is acceptable in justifying land subsidence. مطالعات انجام شده از منطقه مورد مطالعه نشان داد که افت سطح آب زیرزمینی در منطقه خطی است و این در توجیه فرونشست زمین قابل قبول است. Studies of the area showed a decline in groundwater levels in the region is linear in this case is the justification acceptable land subsidence. مطالعات منطقه نشان داد که کاهش سطح آبهای زیرزمینی در منطقه خطی است در این مورد توجیه فرونشست زمین قابل قبول است. Can't load full results Try again Retrying… Retrying… So that the patterns obtained using the radar interferometry method in order to find the pattern of land subsidence and groundwater were consistent and somewhat uniform. In this regard, one of the main causes of land subsidence in the region in Javadabad due to the increasing depth of piezometric wells in the study period can be attributed to the high pumping of groundwater resources. The results of radar interferometry studies have shown that subsidence has occurred at most of the surface of the Jajrud alluvial fan. نتایج مطالعات تداخل سنجی راداری نشان داده است که فرونشست در بیشتر سطح مخروط افکنه جاجرود رخ داده است. As a result of TdakhlSnjy radar studies show most MkhrvtAfknh level Jajrood land subsidence occurred. در نتیجه مطالعات راداری TdakhlSnjy نشان داده شده است که بیشتر سطح مخروتافنکنه فرونشست زمین جاجرود رخ داده است. Can't load full results Try again Retrying… Retrying… According to the physiographic shape of the region and the pattern of land subsidence, the highest rate of land subsidence was observed in areas consist of low slope, including Javadabad and Varamin. In terms of risk, population, housing, roads and buildings, rail roads and important roads are involved in the phenomenon of land subsidence in this region. The railroads of Tehran, Mashhad, Garmsar and Qom are the connecting roads in this region. The occurrence of land subsidence has caused change in the local surface slope and this has caused disturbance in the drainage network and the flow path of surface water, which has ultimately result the occurrence of various types of erosion.