چکیده:
فرونشست زمین یکی از مخاطرات طبیعی است که در اثر عوامل طبیعی و یا ترکیب این دو عامل، به شکل ﻓﺮورﻳﺰش ﻳﺎ ﻧﺸﺴﺖ رو ﺑﻪ ﭘﺎﻳﻴﻦ ﺳﻄﺢ زﻣﻴﻦ رخ میدهد. پایش تغییرات سطح زمین مستلزم استفاده از فنهای دقیق است. در این راستا، فن تداخلسنجی راداری با پراکنش گرهای دائمی با پوشش وسیع مکانی و نیز قدرت تفکیک زمانی و مکانی بالا، یکی از دقیقترین و کمهزینهترین فنهای سنجشازدور جهت پایش و اندازهگیری میزان جابهجایی به وجود آمده در سطح زمین است. در سالهای اخیر، در پی تغییرات اقلیمی و خشکسالیهای پیاپی از یکسو و نیز مدیریت غیراصولی منابع آب، برداشت بیرویه آبهای زیرزمینی و رشد فزاینده جمعیت، سبب رخداد جابهجایی زمین بهخصوص فرونشست دشت شبستر - صوفیان شده است. ازاینرو، این تحقیق با استفاده از روش مذکور و طریق پردازش تصاویر Sentinel-1 بین سالهای ۲۰۱۶ تا ۲۰۲۰، نرخ جابهجایی زمین در این منطقه را مورد ارزیابی و پایش قرار داده است. برای بررسی تغییرات سطح آب زیرزمینی منطقه و تهیه نقشه افت آب همچنین هیدروگراف واحد چاههای مشاهداتی منطقه از دادههای سطح آب بین بازه زمانی ۱۳۸۰ تا ۱۳۹۸ استفاده شده است. نتایج روش پراکنش گرهای دائمی حاکی از نرخ جابهجایی سالانه زمین برای منطقه از سال ۲۰۱۶ تا ۲۰۲۰ به ترتیب ۵۴/۸ –، ۴۷/۹-، ۹/۸-، ۷/۹- و ۰۲/۹ – سانتیمتر بوده است. بدین سبب که منطقه فاقد ایستگاههای ژئو دینامیک و GPS بوده است، اعتبارسنجی نتایج روش تداخلسنجی راداری با استفاده از دادههای چاههای پیزومتری و مقدر افت سطح آب زیرزمینی (۷/۴ متر) در منطقه و تحلیل هیدروگراف واحد آبخوان، همچنین مقایسه نتایج تحقیقات قبلی صحت نتایج تحقیق حاضر تایید گردید.
Land subsidence is one of the natural hazards that occurs as a result of natural factors or a combination of these two factors, in the form of flooding. Monitoring land surface changes requires the use of precise techniques. In this regard, the radar interferometry technique with permanent dispersers with wide spatial coverage as well as high temporal and spatial resolution is one of the most accurate and cost-effective remote sensing techniques for monitoring and measuring the amount of displacement on the ground. In recent years, following climate change and successive droughts on the one hand, and the improper management of water resources, improper abstraction of groundwater and increasing growth of population, on the other hand, has led to land displacement - and subsidence, in particular - on the Shabestar-Sufi plain. Therefore, this study has evaluated and monitored the rate of land movement in this region by using the mentioned method and by processing Sentinel-1 images between 2016 and 2020. To study the changes in groundwater level in the region and to prepare a water drop map as well as the hydrograph of the observation wells in the region, water level data between 2001 and 2017 have been used. The results of the permanent dispersion method indicate the annual land displacement rate for the region from 2016 to 2020 in five periods - 8.54, -9.47, 8-9, -9.7 and -9.02 cm, respectively. Due to the lack of geodynamic and GPS stations in the region, validation of the results of the radar interferometry method was assessed by using piezometric well data and the predominance of groundwater level drop (4.7 m) in the region and hydrograph analysis of the aquifer unit, and by comparing the results of the previous research, and the accuracy of the results of the present study was confirmed. Extended Abstract 1-Introduction Land subsidence is one of the morphological threats for alluvial plains of the country in the last decade. Sufiyan plain is one of the fertile plains of East Azerbaijan province. In this region, groundwater is the main source of water needs, especially agriculture. The expansion of cultivation area, the increase in agricultural activities, the decrease in rainfall as well as the shortage of surface water and the consequent decrease in groundwater reservoirs on the one hand, and uncontrolled abstraction of groundwater, on the other hand, have caused the groundwater level in this plain to decline continuously. The average groundwater drop in this area during the 18-year statistical period has been about 4.7 meters per year. In this research, in order to obtain the amount of subsidence in Shabestar-Sufiyan plain from 2016 to 2020, the method of interferometry of automatic processing with the method of Persistent Scatterer Interferometry instruments has been used. The radar images used in this study included 133 SLC images of the Sentinel-1 sensor related to the low-pass circuit. To analyze the subsidence of Shabestar-Sufiyan plain in relation to the decrease of groundwater level, the data of piezometric wells in the region, which had more complete data, were used to draw a water loss map and hydrograph of the aquifer unit. This hydrograph is to clarify the relationship between water level drop and land subsidence. Finally, the annual movement rate map of the region has been obtained, and by compiling these maps and comparing them with the hydrograph of wells in the region as well as previous research, an acceptable correlation has been obtained. 2-Materials and Methods In this study, In order to monitor the subsidence of the region, the technique of automatic interferometry processing by Persistent Scatterer Interferometry (PSI) has been used. 133 Sentinel-1 single look complex (SLC) products acquired in Interferometric Wide-Swath (IW) mode between January 2016 and December 2020 in descending direction (path 464) were used in this study. As the number of persistent scatterers which can potentially be identified from the time series decreases in the course of time, the investigated time was divided into five intervals of one-year. The master images of each period were selected by minimizing the overall decorrelation of the spatial and temporal baseline as well as the differences in Doppler centroid. To start this automated process, a base image must be selected from the images, which means that technically all images must be combined for processing in the same way. The base image is the image that is placed in the middle of the analysis period. After selecting a base image, the rest of the following images are geometrically recorded relative to the base image. Geometric recording of images is necessary to form interferograms in the next step, which ensures that each terrestrial target corresponds to a similar pixel with the same azimuth and suffering coordinates in both the base and follower images. After the interferograms are created by adjusting the scripts, the contribution of the noise phase and the flat ground phase are removed from them and the separated parts of the images are debugged. At the final stage, additional Stamp entry data includeing the altitude band and latitude and longitude coordinates are generated and prepared in Stamps format to be given to MATLAB. After loading the data in MATLAB, the candidate pixels are selected and the phase noise of each candidate pixel in each interferogram is estimated. After this, the persistent scatter pixels are selected. In the next step, the pixels that have a very high noise are widened to eliminate these pixels. Atmospheric filtering is applied to the data after the entrapment operation has been performed on the interfrograms and after the parallax error caused by their spatial correlation has been removed, a displacement map is created. 3- Results and Discussion In this study, 133 sentinel-1 (SLC) and polarized (VV) images were used to obtain the degree of subsidence of the region. After processing this data, the displacement map was prepared every 5 years from 2016 to 2020 by the method of permanent scattering. The results show a maximum subsidence of 12.1 cm from 22 January 2016 to 23 December 2016, 12.7 cm from 16 January 2017 to 30 December 2017, and 12.2 cm from 11 January 2018 to December 25, 2018, and 12.3 cm on January 6, 2019 to December 20, 2019. The highest rate of land subsidence was related to the period from January 1, 2020 to December 26, 2020 with 12.9 cm of annual subsidence. Distribution of subsidence areas has been observed mainly in the eastern part of the plain (southeastern parts of Nazarloo village to Zinab village) and southwestern plain, from Vayqan to Sharafkhaneh port. 4- Conclusion The results show that areas with high land subsidence rates are consistent with agricultural and horticultural uses, and according to statistics, the largest share of groundwater abstraction is related to this sector. Also, the maps and graphs obtained from the study of pizometric wells in the region, show a continuous decrease in groundwater level during this statistical period. According to the research results, the most important cause of subsidence is the uncontrolled abstraction of groundwater. On the other hand, the rate and range of subsidence obtained between 2016 and 2020 also show the trend of increasing subsidence in the study area. Field observations also confirm the occurrence of subsidence in the last decade.
خلاصه ماشینی:
ازاين رو، اين تحقيق با استفاده از روش مذکور و طريق پردازش تصـاوير ١-Sentinel بـين سـال هـاي ٢٠١٦ تـا ٢٠٢٠، نرخ جابه جايي زمين در اين منطقه را مورد ارزيابي و پايش قرار داده است .
باتوجه به ميزان افت آب هاي زيرزميني و تأثير مستقيم آن بر ميزان فرونشست منطقه ، در تحقيـق بـراي ارزيـابي وضـعيت افت آب هاي زيرزميني از اطلاعات آماري سازمان آب و منطقه اي استان آذربايجان شرقي استفاده شـده و همچنـين بـه منظـور برآورد نرخ فرونشست منطقه نيز از تصاوير ١-Sentinel، بـين بـازه زمـاني ٢٠١٦ تـا ٢٠٢٠ و روش تـداخل سـنجي پـراکنش گرهاي دائمي (PSI)، به دليل قابليـت پوشـش مکـاني وسـيع ، زمـان و دقـت نسـبت بـه ديگـر فـن هـاي سـنجش ازدوري استفاده شده است .
باتوجه به اهميت اين موضوع ، تحقيق حاضر بـا اسـتفاده از ١٣٣ تصـوير راداري سـنجنده ١-Sentinel بـراي آشکارسـازي وضعيت جابه جايي سطح زمين در محدوده مطالعاتي از سال ٢٠١٦ تـا ٢٠٢٠ انجـام گرفتـه اسـت کـه نتـايج آن مـي توانـد در مديريت آبخوان اين دشت مؤثر واقع شود .
آثار بالازدگي لوله چاه ها ناشي از فرونشست زمين در منطقه موردمطالعه (گزارش شرکت سهامي مديريت منابع آب ، ١٤٠٠) مقايسه نتايج پژوهش حاضر با نتايج پيشين نشان مي دهد که در تمامي اين تحقيقات نيز، دليل عمده فرونشسـت منطقـه افت سطح آب ناشي از برداشت بي رويه آب هاي زيرزميني بوده است .
Monitoring of land subsidence due to overexploitation of groundwater using PS-InSAR )Case study: Assadabad city and adjacent plains), Journal of Spatial Information Technology Engineering, 8 )1), 99-79 )In Persian).