Determination of Slip-Rate by Optical Dating of Lake Bed Sediments from the Dasht-E-Bayaz Fault, Ne Iran

Abstract

The Dasht-e-Bayaz left-lateral strike-slip fault in northeastern Iran ruptured in two destructive earthquakes in 1968 and 1979. The western half of the Dasht-e-Bayaz fault cuts across the dry lake-bed in the Nimbluk valley and has no measurable relief except for at a few localised jogs in the fault trace. We provide the first quantitative constraint on the slip-rate of the Dasht-e-Bayaz fault averaged over the Holocene. The western part of the fault cuts across the Nimbluk valley; the flat surface of which is composed of lake-bed sediments. Small streams cut into the surface of the lake-beds are displaced across the fault by 26 ± 2 m. Two OSL samples of the lake-bed sediments are success-fully dated at 8.6 ± 0.6 and 8.5 ± 1.0 ka, from which we calculate a minimum slip-rate of 2.6 mm/yr. This minimum slip rate remains constant with the previously proposed Holocene slip rate of 2.5 mm/yr and within the range of the Holocene slip rate of 2.4 ± 0.3 mm/yr estimated before on the central section of the Doruneh fault.