Combined Interferometry and GPS analysis of Masouleh landslide, North Iran

Masouleh landslide is located near the ancient village of the Masouleh, in the northern province of Gilan, Iran. The landslide is a potential threat for main access road of the village and has also increased the flood risk in the region. Geodetic monitoring of landslide movement is important to characterize its stability and identify its hazardous zones. The aim of this study is to assess landslide movement in Masouleh using combined analysis of GPS measurement and satellite Radar interferometry. 11 ALOS/PALSAR images spanning 2008-2010 were processed using Small Baseline Subset (SBAS) method to produce velocity map and displacement time series of landslide. Furthermore, a network of 24 stations was installed and measured in 3 epochs: November 5, 2015, March 3, 2016 and July 29, 2016. The performance of L-band radar images in the vegetated cover of the landslide was sizably acceptable and the movement regimes of slip zones in landslide body were distinguished separately. The upper part of landslide is almost inactive while the lower part is active and moved with different rates. Results showed significant movements with the rates of up to 51, 46, 70 mm/year for northern edge, older and younger part of landslide respectively. The GPS observations complement radar measurements and show that the most active part of landslide is in the terrace region in the lowest part of the slope, for which radar failed to detect any pixels for deformation analysis. The maximum horizontal displacement for the 8 month time period between November 5, 2015 and July 29, 2016 was 37 cm.