radar interferometry

Land subsidence refers to the gradual or sudden lowering of the earth's surface as a result of various factors such as tectonic activities, mining, oil and gas fields, and illegal extraction of underground water. In Alborz province, the growing trend of population and migration in recent years has added to the increase in demand and the amount of water withdrawal from the underground water table, so it is subject to subsidence due to the sharp drop in the level of underground water. In this research, subsidence was first evaluated using the radar interferometric technique, and then, prone areas were zoned with a multi-criteria algorithm in the time frame of 2016 and 2023. The results of information extraction with interferometric technique showed that the average amount of subsidence in the urban boundaries of Saujblag, Karaj, Nazarabad, Chaharbagh and Fardis is between 15 and 320 mm. According to observations, the highest amount of subsidence is in the eastern part and then in the southern and southwestern parts. According to the estimated results of subsidence risk zoning; The parameters of water level drop, land use, slope and geology, respectively, with weight coefficients of 0.16127, 0.141875, 0.130145 and 0.128474, are the most important factors in creating the risk of subsidence in the study area, which are 31 and 23%, respectively. From the range, it has a very high and high probability of danger. Finally, it can be said that the most important factor in subsidence in the studied area is excessive use of underground water and the drop in water level. In some urban areas, such as Hew and Goch Hesar, Malekabad-Mehrshahr-Mehrvila-Kamalshahr, and Mohammadshahr, the highest risk of subsidence can be seen.

The environmental consequences of land subsidence are destructive, costly and irreparable, and include creating cracks on the surface of the earth, damaging human structures such as building foundations, streets, bridges, roads, and power transmission lines. Sewage is destruction of irrigation systems and fertile agricultural soils and damage to ancient sites. Remote sensing methods, unlike mapping data and topographical maps, which are in physical contact with terrestrial phenomena, are without the slightest interference on terrestrial phenomena, and measuring and evaluating changes in phenomena are evaluated from a distance. Short receiving time and high spatial accuracy of radar images have made it used as a general and widely used tool to estimate land subsidence. According to the statistics announced in the country of Iran, the adverse effects caused by land subsidence are not a low number and are rapidly developing and spreading in different regions of the country. Leave irreparable damage. Ardabil plain, with its rich underground water resources and good soil, has always been of interest in the last half century and has been a suitable place for providing drinking water and agriculture. With the boom of agriculture from the 1960s onwards and as a result the excessive harvest from the aforementioned table since 1363, the aforementioned source began to decline and the continuation of this situation in the following years caused this plain to become more critical.

In order to carry out this research, the data of 22 piezometric wells in the Ardabil plain have been used. The time period used in this research is a 7-year period from 1395 to 1402. The method used for the data of this section is the BRF method, as one of the methods of radial functions, which is used due to its low error value and high accuracy. SAR images of the European Space Agency's Sentinel 1 satellite in SLC format and with vv polarization have been used to find out the changes in land subsidence in the Ardabil plain. The images used by the Sentinel 1 satellite (in c-band with a wavelength of 5.6 cm) are in the group of sensors with medium resolution in terms of spatial resolution. The radar interferometry method provides the possibility of producing a digital model of the ground height, whose optimal height accuracy for c-band data with a wavelength of 5.6 cm is about 5 meters. This method is able to reveal surface changes in the ground in different intervals with millimeter accuracy by using at least 2 or more radar images. In this method, an artificial interferogram is produced with the help of digital elevation model of the earth and conversion of height into phase, and in this way, with the help of reverse DEM data, the phase effect caused by topography is calculated and removed from the phase difference values. The remaining phase difference belongs to the effect of surface displacement and atmosphere.

The results of the investigation of piezometric wells in the area of Ardabil Plain show that the maximum drop in the underground water level is 48.77 meters in the southeast of Ardabil Plain and the lowest drop in the underground water level is 1.57 meters in the north. Eastern Ardabil plain was calculated. The amount of fluctuations in the water level of piezometric wells shows that the highest amount of fluctuations was in the area of Pirqavam wells, Arallovi Bozor and Khalil Abad lands. The lowest fluctuation was also observed in the area of Agchechai wells, Nojedeh. In the studied time period, the water level of Khalilabad piezometric well in 2015 was 2.96 meters, while in 1402, the water level in this area reached 46.3 meters. During 7 years, the water level has dropped by 43 meters, which indicates a critical situation in this sector. The lowest fluctuation of the water level is also for the Aghche-chai well. The land subsidence map of Ardabil plain shows that: the south-eastern parts of Ardabil city and also to some extent in the southern part have suffered ground subsidence due to the extraction of underground water. In the next order, the western parts of Ardabil city are prone to land subsidence. Based on this map, the maximum amount of ground subsidence has been calculated at around 598 mm in the area of Khalil Abad well. In the area of Khalil Abad well, the situation of underground water level drop is very critical and it has dropped by 43 meters during 7 years from 1395 to 1402. The overlapping results of the underground water level and co-depth curves with the results of radar interferometry show the accuracy of the findings in this section. Overlapping the location of the historical sites with the land subsidence map shows that, first of all, Tapraqlu hill (first millennium BC) is in the area of land subsidence with a rate of 250 mm.

The results of the application of this method revealed a very high level of land subsidence for the Ardabil plain (598 mm during a 7-year period). The southeastern areas of Ardabil plain have found a critical situation in recent years due to unprincipled exploitation and lack of proper management. Overlapping the location of the historical sites with the land subsidence map showed that Taparaglu hill with a rate of 250 mm and Ozrik Tepe-si with a rate of 69 mm are in the area of land subsidence, respectively. The three historic sites of Qala-Bovini, Niar Tepesi and Tezre Tepesi are also located in the area prone to land subsidence with rates of 27 mm, 46 mm and 49 mm, respectively. The cause of land subsidence in the Ardabil plain, according to the studies conducted on the changes in the underground water level, is the excessive exploitation of the underground water resources for the cultivation of agricultural products and providing the possibility of compaction of the underlying layers. In general, it can be said that the research results indicate the involvement of historical sites in the area of land subsidence.

Land displacement is known as one of the most obvious invisible effects of natural earthquake hazards. In the present study, the radar interferometric technique (SBAS) using the images of Sentinel 1 (2018 to 2021) was used to estimate the land subsidence, and the Landsat 8 image of 2018 was used to extract the land use classes in a part of the Sarab county. Also, the data obtained from the regional water organization has been used to investigate the condition of underground water in connection with the subsidence caused by displacement. According to the findings and survey of the land use map of the study area, the subsidence can be seen in different places and it reaches 9 cm per year around the agricultural areas and pastures. Also, in some places, the rising rate is estimated up to 12 cm. Examining the condition of aquifers shows a drop in the level of underground water in most stations, especially a sudden drop since the beginning of 2018. Considering that the direct relationship between groundwater withdrawal and subsidence has been fully proven; But after the 5.9 magnitude earthquake in November 2018, sudden changes have occurred in the subsidence of the region. Therefore, it seems that the subsidence of the region is more affected by the earthquake.

The landforms created by tectonic processes are studied by morphotectonics, in other words, morphotectonics is the science of applying geomorphic principles in solving tectonic problems. Quantitative landscape measurements are usually based on the calculation of geomorphic indices, using topographic maps, satellite images aerial photographs, and field visits. Coastal deltas are part of landforms and landscapes that, due to the proximity of two environments, land, and water, leave visible effects against tectonic activities, such as changing the pattern and location of deltas due to the change in the course of coastal rivers, the formation of unbalanced coastal terraces in parts of the coast, and the emergence of cut beaches in the form of seawalls.One of the methods of identifying and measuring land changes is using radar remote sensing. The principles of this technique were first described by Graham in 1974 (Pacheco et al., 2006). Interferometry using radar images with an artificial window or SAR is a precise method based on the use of at least two radar images of the same area, which measures the height displacement changes in wide areas and during different time intervals with a significant accuracy of millimeters (Dong et al., 2018).The coastal areas of northern Iran are of great importance due to the high population density and the ability to grow and develop economically and agriculturally, so monitoring geomorphic changes in the direction of sustainable development of these areas is particularly important.In this research, the eastern coast of the Caspian Sea from Gomishan to Joibar is investigated in terms of subsidence and uplift using radar remote sensing techniques to determine the active tectonic zones of the coast in terms of temporal and spatial changes.

The Eastern Caspian Plain is the border between the Caspian Sea and West Gorgan and includes the cities of Gomishan, Bandare Turkman, Bandare Gaz, Gulugah, Khazarabad, and Joybar. The absolute height of the Caspian Plain along the coastline is determined according to the sea level, based on the hydrographic data of the Baku station, since 1850, the Caspian sea level has varied between -25.4 and -29.4 (Abdolhi Kakrodi, 2012).The history of seismic activity in North Alborz shows that cities like Rasht, Lahijan, Amol, and Gorgan, have been destroyed many times due to destructive earthquakes (Aqhanbati, 2013). The Alborz fault is an active fault that is stretched in a clockwise direction in the southern Caspian basin.In this research, according to the desired goals and radar remote sensing techniques, a series of Sentinel-1 radar images with a suitable time and space difference (maximum 30 days and maximum 150 meters respectively) including 61 images in time from 2014 to 2021 were prepared and processed.

The results obtained from the SBAS model indicate that the eastern part of the Caspian coast is more affected by the uplift and this trend continues up to Gorgan Bay. The Gorgan city has an uplift between 20 and 40 mm/year, which is reversed towards the coastal area, and subsidence of 10 to 52 mm/year occurs, which decreases as it approaches the coast and reaches 10 mm /year.

According to the results obtained from radar interferometry, the eastern coast of the Caspian Sea is more affected by uplifting. The Gorgan city has an uplift between 20 and 40 mm/year, which is reversed towards the coastal area, and subsidence of 10 to 52 mm/year occurs, which decreases as it approaches the coast and reaches 10 mm/year.To verify the results obtained, the data of the Gorgan geodynamic station was used, which shows subsidence of about 90 to 100 mm in a 6-year period, which is consistent with the values obtained from radar interferometry Based on comments Shahpasandzadeh (2013) and the reports of Nazari et al (2021), active tectonics caused by the Caspian fault that indicates the horizontal geodynamic displacement diagram of Gorgan, the small area towards the north and east during this time, which is observed in the form of numerous branches with a thrust (reverse) mechanism and a right-slip component with a slope to the south in Golestan province.Considering that the main feature of the coast of the Caspian Sea is the Surface rivers and the use of groundwater is very little and also the extraction of gas, oil, and mining resources, which is another factor in the occurrence of land subsidence, does not exist in this area, and there isn’t also huge and heavy structure in the study area that affects the subsidence of the surface; so displacement in the study area is the result of active tectonics.

Snow depth plays a critical role as a key input parameter in various agricultural, hydrological, and climatological models. Nevertheless, the process of estimating snow depth through optical remote sensing tools is subject to uncertainties stemming from constraints within the imaging technique. Consequently, the primary objective of this study is to employ active microwave remote sensing technology for the purpose of snow depth estimation in regions characterized by mountainous terrain. The radar interferometric technique employing active microwave imagery was utilized for the specific objective of examining the microwave signal's interaction with snow accumulation. Utilizing Sentinel 1 satellite images of the Zagros mountains in Iran during the months of February 2017, March 2019, and 2020, relevant data was acquired. Furthermore, field measurements of snow depth were conducted to validate the proposed algorithm. In order to enhance the accuracy of snow depth estimations, the data from both VV and VH channels was integrated by applying a weighting factor determined based on the local radiation angle. The comparison between the outcomes of the suggested approach and the field data revealed a correlation coefficient of 0.86. Furthermore, the calculated values for RMSE and P-Value were 14.37 cm and 0.009, correspondingly. Based on the statistical metrics derived from the validation process of the proposed technique, it demonstrated a satisfactory performance in the estimation of snow depth.

Land subsidence is a phenomenon emerging in most of the alluvial plains of Iran in the last few decades due to the gradual or sudden lowering of the land surface. It is prompted by various factors such as over-harvesting of underground water, tectonic activities, mining, etc. Neyshabur Plain is not an exception to this rule and due to the over-exploitation of underground water in the last few decades, the water level of the aquifer has dropped and the hydrostatic pressure has declined. This has led to subsidence, which has affected rural and urban areas. This plain covers an area of 3477 square kilometers, of which an area of 591 square kilometers, which is home to a population of 59,000 people and 179 villages, struggles with severe land subsidence. In this research, the relationship between the aquifer and underground water level and its compatibility with the areas facing subsidence is investigated. Research shows that for every 83-cm decline in  groundwater level, there is on average 10.5 cm subsidence in the surface of Neyshabur Plain. In this research, sentinel satellite images from October 2014 to December 2017 taken by the Mapping Organization have been used by radar interferometric method. The results suggest that the indiscriminate exploitation of underground water resources has triggered land subsidence and cracks in rural areas, especially in the periphery of the villages of Firuzeh, Abu Saadi, Birum Abad, Faiz Abad, Sarab Koushak, Urdughash, and Farrakhk which are in some cases as big as 15 to 20 cm per year. The highest and the lowest subsidence, i.e., 1 cm per year, is reported in the villages of Dasht, Mehdi Abad, and Khoresofla.

Geological processes (tectonics) are formed by forces that originate from the earth's crust and change the shape of the earth's crust. These processes create external forms and landforms such as continents, mountains and oceans, and the set of these processes is called tectonic cycle, so tectonics refers to processes, buildings and landforms. Related are to changes in the shape of the earth. In order to check the tectonic status of a region or basin, there are various methods. In the meantime, geomorphic indicators are a useful and reliable tool in evaluating tectonic activities because they can be used to identify areas that have experienced fast or even slow tectonic activities in the past. Are easily identified. The amount of new land construction activities is different in different regions of the Iranian plateau, among which, Zagros is active in terms of new land construction activities and is associated with many movements. The studies of geostructural processes will be useful for the better management of geomorphological hazards, which are important for many human activities such as the design and construction of cities, power plants, airports, military and security facilities, dams and industrial centers. Also, identifying the features of the environment, the geomorphological forms of a region and being aware of them help us to better understand the environmental capabilities and by providing this information to the authorities, they can use them in the implementation of regional planning. And local, civil planning, land use plans and in general sustainable management of the environment suitable for that area. Considering the importance of the topic, in this research, the tectonic situation of Zagros in Fars province from evaz to Karmostaj has been evaluated.

In this research, the Sentinel 1 radar images, SRTM 12.5 meter high digital model and satellite images are used as the most important research data. The most important tools used in the research were ArcGIS (to prepare the desired maps), GMT (to run the SBAS time series model) and SPSS (to perform the calculations related to the indicators). Also, 10 geomorphic indices and SBAS time series model were used in this research. This research has been done in two stages according to the desired goals. In the first stage, the tectonic status of the region has been evaluated using 10 geomorphic indicators. In the second stage, using Sentinel 1 radar images and the radar interferometry method and SBAS time series, the amount of vertical displacement in the study area has been evaluated. In order to implement the SBAS time series model, first, 21 Sentinel 1 radar images related to a 2-year period (2020 to 2022) have been prepared.

In this research, in order to investigate the tectonic status of the studied area, geomorphic indicators and also radar interferometry method have been used. The results of investigating the tectonic status of sub-basins in the region in terms of IAT index have shown that sub-basin 4 has the lowest average with an average coefficient of 1.5, and overall, in terms of the indicators used, it has a more active tectonic status than other sub-basins. After this sub-basin, sub-basins 6 and 9 have a more active tectonic situation with coefficients of 1.6 and 1.7, respectively. Also, sub-basins 10, 2 and 3 have the highest average with coefficients of 2.2, 1.2 and 1.2, respectively, and in terms of the indicators used, they are tectonically less active than other sub-basins. They have Also, the results of the radar interferometry method have shown that the study area during the studied time period (from 12/01/2020 to 01/01/2022) had 127 mm of elevation and 109 mm of subsidence. . Examining the spatial situation of the vertical movement that has occurred indicates that a large part of the southern anticlines of Lar and Gerash cities has faced subsidence and a large part of the plains of this region has faced uplift. According to these changes, it can be said that the tectonic factor played the main role in the displacement that occurred in the region.

The results of this research have shown that the studied area is tectonically active. Also, in this research, the relationship between the amount of vertical movement of the region and geomorphic indicators has been investigated. First of all, it should be said that the correctness of the geomorphic indicators is confirmed, because based on the radar images, the studied area is tectonically active. But the remarkable thing about the results obtained from the radar images is the type of displacement that occurred and the effect on the geomorphic indicators. In fact, as it was said, the plains of the region are elevated and this problem has caused the difference in the height of the basin to decrease. Based on this, the type of vertical displacement of the region has caused some indices such as Hi, Bs, SI, S and Gi to show the tectonic activity of the region less than it is. In total, the results obtained up to this stage have shown that some geomorphic indicators show the tectonic status of the region less than the actual value.

Investigation and monitoring of displacement field due to deformations of the earth's surface is one of the most important and applied studies in various topics such as geology, geomorphology, geophysical. Land subsidence is one of the destructive geological phenomena that can cause irreparable financial and life losses. In fact, subsidence is a morphological phenomenon that in the logical state of this phenomenon includes collapse or downward sitting of the earth's surface, which can also have a small horizontal displacement vector (Solari et al., 2018). This phenomenon has been charted as a serious crisis in most plains of the country in recent years. Therefore, identifying and reducing the consequences of subsidence phenomenon requires a monitoring system. Several methods have been proposed to accurately evaluate and measure this phenomenon, which radar interferometry technique was introduced as one of the methods of radar image processing in active remote sensing, a useful tool in monitoring the placements of the earth's surface (Sadeghi et al., 2012).So that over the past several years, the use of radar interferometry technique to evaluate and monitor land subsidence has increased and its time series algorithms such as PSI and SBAS have provided the possibility of measuring ground displacements (Abu pit et al., 2010). Therefore, in this study, we tried to estimate the time series of kermanshah plain subsidence during 2016-2021 using Sentinel 1 satellite imagery and using radar interferometry technique under small baseline length approach.

Radar interferometry with artificial valve is a remote sensing technique. In which two or more radar images are used to produce digital elevation models or to map the displacement of the earth's surface. In this technique, the phase difference between two different waves is measured and this phase difference is attributed to the change in distance between the sensor and the ground target or the displacement of the earth's surface. Ideally, each interferogram should have only a phase difference caused by the displacement of the earth. For this reason, other components must be removed or deducted so that the remaining phase can be obtained only from displacement. In the above article, using radar data and using radar interferometry technique and small baseline time series analysis, the time series of land subsidence phenomenon in Kermanshah plain is monitored and measured. In this method, only visual couples are used that the vertical component of the baseline is less than the critical value of the baseline. Also, their time baseline is minimized at the same time. In this way, only interferences are formed that have good quality. Then, the results of this method, which is the average annual subsidence map in the desired period, are investigated to explain the relationship between the cause of subsidence occurring on the plain surface with changes in groundwater level and the thickness of fine sediments.

In order to investigate the behavior pattern of the earth surface in the long term, we used time series analysis using small baseline method. To do this, among multiple images and interferograms, 36 radar images were selected from sentinel 1 sensor at the time interval of 2016 (June) to 2021 (January) and selected by the lowest baseline of 88 interferograms that had a suitable spatial and temporal baseline and were dispersed in the interferometry process. After obtaining the interferogram images, the noises in the mapping interference must be removed so that the residual noise is only due to the displacements of the earth's surface, resulting in the average map of the earth's surface displacements in the desired timeframe. Evaluation of the obtained map indicates maximum subsidence of -100 mm/year in the western parts of the plain. Then, by preparing a map of water level drop in the plain, the relationship between these two variables was investigated, which did not show a significant correlation between them, so by examining another effective factor in the plain surface, we realized that in addition to the drop in the water level, the thickness of fine sediments should also be considered because by summing these two factors together, the surface subsidence. The earth intensifies. This is well known in the western parts of the plain

The maximum subsidence calculated between 2016 and 2021 is 10 cm, which covers an area of about 1.67% of the total area. Then, in order to explain the cause of subsidence occurring in the region, we investigated the relationship between groundwater level drop and subsidence in the region. By evaluating 54 piezometer wells in the plain, it has been observed that the maximum subsidence range is not in accordance with the maximum drop in water level. Therefore, we were looking for another effective factor in the plain surface that by studying the thickness of fine sediments (clay and silt) in the maximum subsidence range, we saw a high thickness of fine sediments which has experienced a moderate drop from the water surface about 5 meters per year. Therefore, it is not always possible to see the linear relationship between water level drop and land subsidence.investigation of steady state index showthebarchan dunes, with annual displacement rate more than 12 meters,have the maximum number and highest rates of displacement, and have the lowest steady state. Thus this group is demanding the more attention and planning requirements for stabilization of quicksand and environmental management of mobile barchan dunes.

Land subsidence is a geological hazard that occurs in connection with human activities and environmental changes. This hazard has occurred in 60 countries and more than 150 cities of the world. Similar to many regions of Iran, the southern plains of the Alborz mountain range are facing rapid land subsidence in connection with excessive extraction of groundwater. Considering the average water consumption and the scattered data related to the drop in the underground water level in the country, it is not difficult to recognize that subsidence and its consequences have become a problematic phenomenon in the country. In recent years, many cracks have appeared in agricultural lands and residential buildings, streets and infrastructures of the study area; In such a way that in the agricultural sector of the region, it has caused the destruction and destruction of part of the lands, and in the residential sector, it has caused successive settlements in the buildings and caused irreparable damages.

In this research, data analysis was done in several stages, which are described below. In the first stage, using the information related to the water level drop of the wells in the studied basin, the amount of changes in the water level of the wells was calculated and then a map of the groundwater level drop in the studied basin was prepared. In the second step, using Sentinel 1 images for a period of 5 years (January 2017 to January 2022) and using the SBAS time series method, the amount of subsidence of the studied basin has been calculated. At this stage, the desired images with 24-day intervals have been prepared. After preparing the images, Linux operating system and SNAP software have been used to process the images. In the next step, the correlation between the amount of subsidence with the state of groundwater level drop in the region and other geomorphological parameters has been evaluated, for this purpose, the interpolation map related to the drop in the groundwater level of the region was entered into SPSS software in pixel format and then the subsidence map was also created. In the same way, it was entered into the SPSS software, and in this way, the relationship between the amount of subsidence and the groundwater loss of each pixel was evaluated together. At this stage, using the integrated model of fuzzy logic and AHP, areas prone to subsidence have been identified. To do this, first, the desired parameters including lithology, height, slope, the amount of groundwater loss, proximity to the river and topographic units have been selected. After preparing the desired information layers, the layers are scaled based on the subsidence potential. After fuzzy membership of the layers, the layers are weighted based on the opinions of experts (3 Geomorphologists) and the Analytical Hierarchy Model (AHP) and finally, the layers of information are combined using the fuzzy gamma operator and the final map of the areas prone to subsidence is prepared.

The area of Hashtgerd Plain lacks the variety of geomorphological landforms and is mainly located on the plain and old conifers. The absence of geomorphological barriers has made the residential and agricultural development in this area not to face much restrictions. Therefore, in the period of 30 years, there have been major changes in the land use of the region. The land use map of the studied area during the years 1990 to 2020 shows the increase of residential and agricultural uses. According to the results of calculating the water level drop in the studied wells, in this research, using the spline interpolation method, an annual groundwater drop map has been prepared in the study area, based on this, the middle and southern areas of the range Studies have the highest average annual groundwater level drop.
The correlation between the annual average drop of the underground water level and the amount of subsidence has been evaluated, and the results show that the correlation coefficient between them is about 7%. According to the results, it can be concluded that the Hashtgerd range has experienced subsidence between 18 and 320 mm in our five-year period.

Land subsidence will ultimately be the "death of the aquifer" and the destruction of agriculture and horticulture in the Hashtgerd Plain. With the continuation of this process, the fertile lands of Hashtgerd region will face a dark prospect and irreparable social and economic effects will affect the region. The results of radar interferometry indicate that the amount of subsidence in the study area during a 5-year period is between 18 and 32 cm. The final subsidence map shows that the highest amount of subsidence is in the southern and western areas and the lowest amount is related to the northern areas of the study area. Based on the assessment of areas prone to subsidence risk, it can be seen that the results of radar interferometry are highly reliable to a significant extent.

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.

Khanmirza plain is one of the plains of cold and temperate regions of Iran, with an average rainfall of 500 mm per year and sufficient nutrition in terms of surface resources, the subsidence event is currently happening in it with a rapid trend. In terms of geostructure, Khanmirza plain is located in the folded Zagros zone in the south of the Dana fault, and the presence of piezometers protruding from the soil, as well as the presence of springs, etc., are signs of crustal movement on the surface of this plain. For this purpose, with the aim of evaluating the tectonic activity of the region in creating the phenomenon of subsidence from some geomorphic indices such as basin shape index (BS), river longitudinal gradient (SL), drainage basin asymmetry (AF), reverse topography symmetry index (T), integral index Hypsometry (H) of the region's subsidence was studied tectonically. Likewise, the subsidence rate was determined using radar interferometry. Examining these indicators showed that the indicators of basin shape (BS), river longitudinal gradient (SL), drainage basin asymmetry (AF), reverse topography symmetry index (T) are active tectonics in the region. Earth construction activities have caused the plain to stretch and become asymmetric on both sides of the main river. Likewise, the results of radar interferometry in the two-year period indicate that parallel to subsidence (at a rate of 9 cm) in some parts of the plain, other parts are facing uplift (at a rate of 21 cm).Collapse and subsidence can be caused by natural geological phenomena such as earthquakes, dissolution of limestone, chalk and salt rocks, melting of ice and compaction of deposits, slow movements of the crust and the release of lava from the solid crust of the earth, or activities human activities such as mining, extracting underground fluids such as underground water, oil or gas (Galloy and Barbie, 2011: 1459). Radar interferometry has been widely used by Earth researchers since the early 1990s (Shirani et al.: 2013). This technique can be used to measure displacements resulting from many phenomena such as earthquakes, landslides and subsidence. In general, there are nearly six hundred plains in Iran, and it is likely that more than half of them are subject to subsidence (Kia Sharifi, 2010: 58).

In order to evaluate the tectonic situation of the region, from topographic maps 1:50000 and geological map 1:100000 to calculate basin shape index (BS), river longitudinal gradient (SL), drainage basin asymmetry (AF), symmetry index Inverted topography (T), hypsometric integral index (H) from (DEM) 30 meters and topographic map were used, which were processed in GIS environment. D-InSAR radar images were used in the period from 2003 to 2005, which were processed in ENVI 5.3 software. Radar interferometry technique

How to calculate the SL river gradient index: The SL index is calculated for the middle point between two flow curves. Symmetry index of transverse topography (T): this index can also specify the state of symmetry and, as a result, the active or inactive state of the region. Drainage basin asymmetry index (AF): The asymmetry index is a method to evaluate the existence of tilts caused by tectonic activities at the scale of the drainage basin. Basin Shape Ratio Index (BS): Basins that have an elongated shape are tectonically active. And the shape of basins that are tectonically inactive tends to be round. Integral Hypsometric Index: Integral Hypsometric is an index that calculates the height of the entire area in relation to the area of the entire area. The values of this index show the transformation stages of the landscape in the erosion cycle. Today, radar interferometry, as a technique that estimates the displacement of the earth's surface with high accuracy and resolution, is a common tool for investigating the change of the earth's surface due to various factors, including land subsidence. In this technique, an interferogram can be prepared using two satellite images. So that by using the interferometric tool, the phases of the return signal from the ground are subtracted from each other in two time-delayed satellite images of the same region to extract changes in the ground surface. The radar interferometry technique uses Sarscape software as one of the powerful tools in the digitization of satellite images to survey the changes in the earth's surface. In this research, 12 Envisat satellite images from the European Space Agency were prepared

 The amount of subsidence calculated from 10 paired images is 9 cm drop in a two-year period, and the amount of elevation obtained from the images was calculated as 21 cm in a two-year period. By comparing these two numbers, it can be concluded that in this basin, the uplift rate is twice as high as the subsidence rate.The obtained values show that in addition to groundwater extraction as one of the main and common causes of subsidence, considering the tectonic factor in areas such as the Khanmirza watershed with high rainfall input is one of the main reasons for its formation.

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 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.

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

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.

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.