Abstract
Abstract. Rock salt has remarkable mechanical properties and high economic importance; however, the strength of salt compared to other rocks makes it a rather vulnerable material. Human activities could lead to acceleration of the dissolution of soluble rock salt and collapse of subsurface caverns. Although sinkhole development can be considered a local geological disaster regarding the characteristic size of surface depressions, the deformations can result in catastrophic events. In this study we report the spatiotemporal evolution of surface deformation in the Solotvyno salt mine area in Ukraine based on Sentinel-1 interferometric synthetic aperture radar measurements. Although the mining operations were finished in 2010, several sinkholes have been opened up since then. Our results show that despite the enormous risk management efforts, the sinkholes continue to expand with a maximum line-of-sight deformation rate of 5 cm/yr. The deformation time series show a rather linear feature, and unfortunately no slowdown of the processes can be recognized based on the investigated 4.5-year-long data set. We utilized both ascending and descending satellite passes to discriminate the horizontal and vertical deformations, and our results revealed that vertical deformation is much more pronounced in the area. Analytical source modeling confirmed that the complex deformation pattern observed by Sentinel-1 radar interferometry has a direct connection to the former mining activity and is confined to the mining territory. With the 6 d repetition time of Sentinel-1 observations, the evolution of surface changes can be detected in quasi real time, which can facilitate disaster response and recovery.
Highlights
Large-volume rock salt deposits formed in the Carpathian– Pannonian region in its both internal and external parts during Badenian times, when those areas were communicating with each other
The spatial pattern of the surface deformation computed from the ascending satellite pass data clearly shows the circular outline of the deforming area around the main sinkhole
The mining area has become a natural laboratory, where salt karst processes evolving much faster than in carbonate rock can be studied in great detail
Summary
Large-volume rock salt deposits formed in the Carpathian– Pannonian region in its both internal (in the Transylvanian Basin) and external (along the outer margins of the Carpathian fold-and-thrust belt) parts during Badenian times, when those areas were communicating with each other. The Transylvanian Basin is a place of unique rock salt storage, where salt layers of a few tens of meters thick were deposited and later deformed by diapirism. Large volumes of salt migrated towards the margins of the basin due to the uneven loading of the overburden, forming two basin margin-parallel belts of large-sized diapirs (Krézsek and Bally, 2006). The salt layer deposited at the outer margin of the Carpathians was deformed, generating diapiric bodies known and exploited at many locations along the East Carpathians and South Carpathians in Ukraine and Romania. Solotvyno (Aknaszlatina, according to its local Hungarian name), located at the Ukrainian side of the northern East Carpathians, is one of them.
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