The Kopeh Dagh Fault system runs along the mountain belt of the same name straddling the border between northeastern Iran and Turkmenistan. It accommodates the northward push of Arabia into Eurasia in this region through a mix of right-lateral strike-slip and reverse faulting, folding and uplifting the Kopeh Dagh ranges over millions of years.
The system is made of several major fault strands, including the Main Kopeh Dagh Fault, that slip at rates of a few millimetres per year. This distributed deformation produces frequent damaging earthquakes across a broad zone, threatening cities such as Mashhad in Iran and Ashgabat in Turkmenistan.
The catastrophic 1948 Ashgabat earthquake (magnitude ~7.3) devastated the Turkmen capital and killed an estimated tens of thousands of people, one of the deadliest quakes of the twentieth century. Historical accounts also record repeated destructive shocks near the Iranian city of Mashhad, underscoring the Kopeh Dagh's long record of major seismic events.