InSAR constraints on the active deformation of salt diapirs in the Kalut basin, Central Iran

Abstract

In recent years, salt diapirs have been widely used for gas storing, hazardous waste disposal, mining, and petroleum production. The rate and pattern of active movement in salt structures are crucial to be obtained before planning these industrial utilizations. The central basin of the Iranian plateau represents well-exposed and -preserved diapirs that can be considered as an analog for other salt basins around the world where the exposures are not as good. Integration of the Interferometric Synthetic Aperture Radar (InSAR) technique with remote-sensing structural mapping permits us to study the active surficial deformation of eight salt diapirs in the Kalut basin in central Iran. We classify the Kalut diapiric structures into salt walls, massifs, stocks, and welds. We then use 75 Single Look Complex (SLC) IW scenes acquired on the ascending collected from November 2014 to November 2018 and 62 SLC images on descending geometries collected from October 2014 to January 2018, both covering the same period. The Sentinel-1 images are processed by the Small BAseline Subset (SBAS) approaches to define vertical and horizontal displacement maps revealing that the Kalut basin is one of the most-active present-day diapiric systems in the world, its eight salt diapirs are rising, and none of them subsides. Maximum calculated rates of growth reach 8 mm/yr in vertical and ~ 2 mm/yr in horizontal directions, suggesting that in general vertical displacements play a significant role in the deformation of this salt-controlled basin. Salt stocks are uniformly rising in their crestal domain (up to 8 mm/yr) with lateral spreading along their flanks (1–2 mm/yr). The larger salt walls are more active and rising faster (8 mm/yr) than smaller ones (3 mm/yr), while welded areas are inactive. These rising salt diapirs are flanked by seasonal depocenters accumulating up to 10 mm/yr of fluvial, evaporitic, and aeolian deposits.