رفتارسنجي توده لغزشي دوپيق در حوزه آبخيز اهرچاي با استفاده از روش پردازش پراكنشگرهاي ثابت تداخل‌سنجي راداري و GPS سه فركانسه

Monitoring of Dopiyagh landslide in the Ahar-chaiy basin based on PSInSAR method of RADAR Interferometry and 3D GPS

زمين لغزش ­ها يكي از رايج ترين و خطرناك ترين تهديدات طبيعي در جهان هستند كه باعث خسارات قابل توجه و زيان هاي اقتصادي مي شوند. شناسايي و نظارت بر زمين لغزش ­ها، دو جنبه تحقيق قابل توجه براي تحليل زمين لغزش­ها است. امروزه، پردازش تداخل ­سنجي راداري يكي از ابزارهاي موثر در پايش زمين ­لغزش ­ها است. روش پراكنشگر دائمي(PSI) يكي ازتكنيك­ هاي­ پيشرفته تداخل ­سنجي بوده كه باعث بهبود دقت نتايج نسبت به ساير روش­هاي متداول تداخل­ سنجي شده است. هدف اصلي اين تحقيق، آشكارسازي و پايش زمين ­لغزش ­هاي زيرحوزه اهرچاي با استفاده از روش پراكنشگر دائمي(PSI) بوده است. داده ­هاي مورد استفاده شامل 22 تصوير ماهواره­ اي ENVISAT-ASAR در مدار پائين­ گذر بوده است. نتايج حاصل از پردازش تداخل ­سنجي راداري با مشاهدات زميني از طريق GPS سه فركانسه مقايسه گرديد. در حاليكه نتيجه مشاهدات بيانگر عدم فعاليت توده لغزشي دوپيق بود ولي نتايج پردازش اينترفرومتري نشان داد كه سطح توده­ه لغزشي دوپيق هنوز هم فعال است. محاسبه نرخ جابجايي سطح زمين در PS شاسايي شده در سطح توده لغزشي مورد نظر نشان داد كه متوسط سالانه نرخ تغييرات سطح زمين در اين توده لغزشي 12/4 ميلي متر در سال در بازه زماني 2003 تا 2010 بوده است. لازم است احتمال ناپايداري­ هاي دامنه ­اي موجود در منطقه، با بكارگيري تكنيك­ هاي جديد پردازشي و داده ­هاي بروز و قابل دسترس راداري بررسي شده و نتايج حاصله جهت انجام اقدامات مقتضي در اختيار برنامه­ ريزان و مديران قرار گيرد.

Monitoring of Dupiagh landslide in the Ahar-chaiy basin based on PSInSAR method of RADAR Interferometry and GPS Introduction Landslides are one of the most common and dangerous threats in the world that generate considerable damage and economic losses. Landslides detection and monitoring are two important research aspects of landslides analysis. There are different geodetic and non-geodetic methods to measure slope instability. Geodetic methods includes ground observations via GPS, Total Station and laser scanners. Observation based on mentioned methods provide accurate and continuous measurements at limited points in unstable regions, but none of them has the ability to determine the extent and pattern of spatial unstable regions. On the other hand, the repetition of each of these methods, especially when it is intended for a large area, is very costly and time-consuming. The existence of such constraints has always been one of the fundamental challenges faced by researchers in relation to precise measurements and spatial monitoring of land surface changes. Due to the fact that landslides directly affect the surface of the earth, the use of remote sensing techniques in instability studies of the slopes seems to be very suitable. Among the remote sensing techniques, radar interferometry (InSAR), capable of working in all weather conditions and the duration of night and day, is one of the most effective and efficient techniques for detecting and monitoring the steady change of the earth's surface. Of course, the lack of spatial and temporal correlations in available radar images limits the use of conventional radar interferometry to monitor the displacement of ground level. Persistent Scatter Interferometry (PSI) is the advanced InSAR technique which has significantly improved upon traditional InSAR methods by increasing the accuracy of results (millimeter scale precision). The main objective of this project was to detection and monitoring of Ahar Chai sub basin landslides based on PSI technique. Matherials & Methods This landslide with an area of about 42 hectares is located near the village of Dupiagh, located in Ahar city and 22 km on the Ahar-Varzaghan axis, in East Azarbaijan province, Iran. The geographical coordinates of the study area is N38 29´ and E46 49´. For detection and monitoring of the landslide, the PSIn-SAR method was implemented on 22 ASAR images (with descending orbital modes) recorded between October, 20030502 and 20100709 by ENVISAT satellite in VV Polarization. For detection and monitoring of Dupiagh landslide, the PSInSAR method was implemented on mentioned ASAR images. SARscape5.2 software on the platform of ENVI 5.3 was employed to process the radar images and to extract the persistent scatterers. The PSInSAR processing technique was performed within five stages including: (1) selection of master image or connection graph selection. (2) Interferometry or interferometric workflow stage consisting of co-registration and differential interferogram generation parts. (3) First step inversion for selection of the candidate persistent scatterer points. (4) Inversion: second step including phase unwrapping and filter implementation stages. (5) Geocoding or conversion of the phase into displacement. Finally, The PSInSAR method results compared with dual-frequency -GPS measurement. Discussion of Results & Conclusions Based on the ASAR images processing by PSInSAR method, results showed that some parts of Dupiagh landslide are still active and displacement rate of the this landslide was obtained 12.4 mm/year duration of 2003 to 2010. While, the ground surface displacement velocity was estimated between 58 to -22.5 mm/year in the Ahar Chaiy sub basin duration the mentioned period. The results of GPS measurement indicated that the Dupiagh landslide was inactive duration of observation baseline. Differential RADAR Interferometry (DInSAR) method in detection and monitoring of landslides has been reported in numerous studies. Also, the study suggests that PSInSAR is a powerful technique to determine displacement and spatial pattern of landslides.