Subsidence monitoring in the Imereti lowland (the Big Sochi region) using multifrequency InSAR data for 2007-2019

Abstract

The results of InSAR based estimation of subsidence of the surface and infrastructure of Olympic Park in the Imereti lowland are presented. We incorporated multifrequency SAR images covering the 12-year period from 2007 to 2019: ALOS-1 (18 acquisitions for 2007-2010), Envisat (13 acquisitions, 2011-2012), Sentinel-1 (more than 300 acquisitions, 2015-2019). Using the SAR data we identified 6 subsidence areas in the Imereti lowland. For the past two years maximum values of total subsidence have reached 150 mm. To process the images, we used ENVI SARscape and PS Stamps/MTI software. For all the datasets, we present maps of surface vertical displacements. Vertical movements were estimated as vertical projection of the line-of-sight displacements assuming horizontal displacements being negligibly small. That assumption was verified by comparing results from ascending and descending tracks. For each of the six subsidence areas, time-series of vertical displacements were compiled using all datasets available. The time-series graphs made it possible to identify the periods of stability and changing in time subsidence, correlate them with construction works being under way. The InSAR based displacement maps are in good agreement with field data. The identified subsidence is quite strong, thus regular monitoring of displacements of surface and infrastructure in the Olympic Park area incorporating InSAR methods is worthwhile.