Tuzla is well known for salt mining. Previous research found that the massive exploitation activities of salt mining have caused up to 12 meters of ground subsidence. These results were obtained by an analysis of the time series topographical data from 1956 to 2003. Abandonment of salt exploitation in center of Tuzla was lasting from 2001 and finally finished in 2007. Subsidence causes damage to buildings and infrastructures. Other research using a GPS survey has revealed that subsidence was ongoing from 2004 to 2007. The GPS results showed that the subsidence was decreasing. However, the subsidence is still ongoing in center of Tuzla City, especially in an area near new salt-water lakes for swimming.
In this research, the Differential Interferometry Synthetic Aperture Radar (DInSAR) method was applied to measure the present subsidence in Tuzla. The main purpose of this research is to enhance the ground subsidence information on the spatial distribution and temporal transition. The Small Baseline Subset (SBAS) time series approach is employed. Sentinel-1 data from October 2014 to November 2017 is used to generate the time series of the ground subsidence. The DInSAR results show that the ground subsidence is still ongoing in some areas. The maximum subsidence velocity is about 40 mm/year. This means that continuous subsidence monitoring is very important. In addition, a comparison of the subsidence obtained by DInSAR and GPS is analyzed and discussed in this work.
Ground subsidence has been a major man-made hazard in Tuzla since 1950. The main factor in this ground subsidence is the salt mining activities (Mancini et al., 2009a). Ground subsidence of up to 12 meters was reported during the period of 1956 to 2003 (Mancini et al., 2009a). Research on ground subsidence was continued by means of static relative GPS positioning conducted four times between 2004 and 2007 (Stecchi, 2008). The GPS results from 2004 to 2005 show that the ground subsidence velocity was about 100–200 mm/year. From 2005 to 2006, the ground subsidence decreased to 0–50 mm/year. In a limited area near the salt-water swimming lakes, however, the subsidence velocity was still close to 200 mm/year. The subsidence gradually decreased from 2006 to 2007, except for the area near the salt-water swimming lakes where the subsidence velocity was about 100 mm/year.
Currently, three GNSS stations are installed and in operation to monitor the ground surface movement. The three stations are located in Tuzla (reference point), Tušanj, and Pannonica (Čeliković, 2016). These GNSS stations provide real-time ground subsidence monitoring. However, the subsidence monitoring results of GNSS lack spatial coverage. Spatial coverage is important to understanding the behavior of subsidence itself.
