Holocene slip-rate of the Gowk strike-slip fault and implications for constancy of slip-rate on the faults of eastern Iran

Temporal variations in fault slip-rate have been suggested to occur in many deforming parts of the world - including eastern Iran. We provide the first quantitative estimate of the late Quaternary slip-rate on the Gowk strike-slip fault in eastern Iran. We estimate a minimum right-lateral slip-rate of 3.8 +/- 0.7 mm/yr, which is considerably higher than the previously assumed value of ~2.5 mm/yr, and indicates that the Gowk fault is one of the most important structures in the accommodation of regional tectonic strain in eastern Iran. Our estimate accounts for previously suggested regional discrepancies between geodetic and longer-term estimates of fault slip across eastern Iran, and argues against temporal variations in slip-rate within the Holocene of eastern Iran. The main active strand of the Gowk fault cuts lakebed sediments within the South Golbaf pull-apart basin. Numerous channels incised into the palaeo-lake surface are displaced right-laterally by 30 +/- 5 m at the fault. Radiocarbon dating of two terrestrial plant fragments constrains the lake desiccation at a maximum of 7.9 +/- 0.1 ka, from which we estimate a minimum slip-rate for the Gowk fault of 3.8 +/- 0.7 mm/yr. The Gowk fault has generated five destructive earthquakes in the past thirty years. At a minimum rate of 3.8 +/- 0.7 mm/yr the average interval between earthquakes, assuming that the fault typically fails in events involving ~3 m of slip, will be 660-960 years. The southern ~90 km of the Gowk fault (the Sarvestan segment) has no record of historical earthquakes and constitutes a considerable remaining hazard in this region.