Using Envisat InSAR time-series to investigate the surface kinematics of an active salt extrusion near Qum, Iran

• Displacements all over an active salt extrusion are monitored to sub-mm accuracy using InSAR.
• A Small-Baseline subset of data are used to define times series over a 5 year interval.
• The pattern of salt deformation displays a clear seasonal effect.
• The salt extrudes continually but flows downslope fast when wet.

Lower Oligocene-Miocene rock salt is exposed in several diapirs in the central plateau of Iran along the northern margin of the Great Kavir basin. These include a small but mature salt extrusion known as Qum Kuh located near the city of Qum. We use small-baseline interferograms to study the surface displacements of Qum Kuh. The interferometric dataset consisted of 149 interferometric displacement maps derived from 35 C-band ASAR images collected by Envisat satellite in both descending and ascending orbits from 2003 through 2009.The results of the displacement time series analyses show significant long-term trend of horizontal motion toward gentle slopes of Qum Kuh, punctuated by seasonal variations during dry and wet seasons. Interferometric Synthetic Aperture Radar (InSAR) time series results suggest that the salt near the spreading center, where the salt first surfaces from depth, is extruded to the more gentle flanks of Qum Kuh and that down-slope gravitational spreading of the extruded salt accelerates when it is wet.