Evaluation of Gougerd slope instability caused by landslide using Differential SAR Interferometry and GPS observation

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