This study focuses on the eastern part of the Khazar Fault Zone, situated in N-NE Iran between the South Caspian Basin, Kopeh Dagh, and the Alborz Mountains, with the Gorgan Plain within it, as part of the seismically and tectonically active Alpine-Himalayan Mountain Belt. Additionally, widespread land subsidence is occurring in the Gorgan Plain, making the investigation of this region crucial. The aim of this research is to monitor surface deformation in the study area, assess its relationship with tectonic activity to minimize and mitigate potential hazards, and provide insights into the tectonic model of the region. We processed LiCSAR interferograms with LiCSBAS using Sentinel-1A images from January 2015 to March 2023 (descending track) and December 2023 (ascending track), calculating mean line-of-sight (LOS), vertical, and lateral velocities for the study area. Aqqala town and the eastern Gorgan region, situated on the footwall of the Khazar Fault Zone, experience the highest vertical deformation rates, reaching approximately −118.81 mm/yr and −146.20 mm/yr, respectively, over an 8-year period. Moreover, the left-lateral movement rates along the eastern section of the Khazar Fault Zone range from a mean of 3.79 mm/yr to a maximum of 8.46 mm/yr, with displacement decreasing from east to west. The results show that the eastern part of the Khazar Fault Zone is active with a left lateral component and indicate the presence of a likely NE-SW trending, north-dipping reverse/thrust fault beneath the Gorgan Plain, which is identified as the Aqqala Fault. It seems that the Aqqala Fault identified beneath the Gorgan Plain may be the source of significant seismic activity, as indicated by the earthquakes with magnitudes ≥ 5 Mw that occurred on October 7, 2004, and January 10, 2005. Our findings clearly show that the deformation in the region is controlled not only by anthropogenic factors, as mentioned in previous studies but also by tectonic activity. These findings demonstrate that the study area is highly active and poses a significant earthquake hazard, highlighting the urgent need for appropriate measures to be taken to address this concern.
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