The Zagros fold-and-thrust belt runs some 1,500 kilometres across western and southwestern Iran, from the Turkish border to the Strait of Hormuz. It marks the crumpling front where the Arabian Plate collides with and pushes beneath the Iranian block, raising the long parallel ridges of the Zagros Mountains.
This is a compressional zone dominated by reverse and thrust faults, many of them blind faults hidden beneath folds of sedimentary rock. The convergence, about ten millimetres per year, produces very frequent moderate earthquakes spread across a wide belt rather than concentrated on a single master fault.
The belt generates thousands of tremors each year and damaging shocks such as the 2017 Sarpol-e Zahab earthquake (magnitude 7.3) on its northwestern edge, which killed more than 600 people along the Iran–Iraq border. Its diffuse, folded structure makes individual ruptures hard to forecast but keeps the region among the most earthquake-prone on Earth.