Does weather move earth? : testing proposed weather event impacts on surface salt motion via interferometry of synthetic aperture radar

Abstract

Rock salts are known to be highly soluble in water since these are mainly composed of halite. The concept of weather affecting the motion of rock salts that are exposed to the surface is established, and ground-based observation of such phenomenon has been reported by a previous study. Meanwhile, remote-sensing observations remain unsuccessful in exploring the weather-surface salt motion relationship due to low spatial and temporal resolution of ground motion data. Here, we present spatially-resolved ground displacement across two surface salt structures, at Mt. Sedom (Israel) and the Dashti salt dome (Iran), using the Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) technique for Sentinel-1 radar imagery acquired between 2015 – 2018, followed by time-series and correlation analyses between the ground displacement and weather observations. Compared with previous studies that used images with 36 days’ temporal resolution, the images used in this study have a best temporal resolution of 6 days in Mt. Sedom region and 12 days in the Dashti salt dome. Salt motion in response to precipitation was reported to last for a week in a previous ground-based study, however, our correlation analyses suggests there is no immediate response of ground motion to weather events in Mt. Sedom, potentially due to the thick caprock, and the response of the Dashti salt glacier to weather appears to be under the detection limit. Moreover, active diapirism of the Dashti salt dome and resulting decorrelations of scatterers may account for our non-successful observation in the region. Lastly, we calculated the vertical uplift rate in the two distinct uplift centers at Mt. Sedom: 1.85 mm/yr in the northern block and 2.60 mm/yr in the southern block. These uplift rates are ~5 mm/yr lower than prior interpretations from lower-temporal resolution InSAR analyses, suggesting mis-estimation of rate of vertical ground motion in the previous studies that consider displacement along the line of sight solely from either the ascending track or the descending track.