This article uses, for the first time, the absolute age for a Qanat system, to determine the slip rate of an earthquake fault. In Iran, many ofQanat galleries were dug in the vicinity of, or directly upon, active faults. In some areas such as Dasht-e Bayaz fault, line of craters are displaced by the activity of the fault, which lead to dry Qanat stream, and consequently to dig new shafts by habitants. By means of measuring the offset between new shafts and old shafts, and considering Qanat antiquity, the estimation of fault slip-rate, which is one of the prominent elements in hazard assessment, becomes possible. This study uses absolute age for a Qanat system, obtained through optically stimulated luminescence dating of grains in spoil heaps of Qanat wells. Feldspar single-grain dating of silt sediments that overlie the construction spoil show that the Miam Qanat was maintained until at least 1. 6-2. 6 ka. Combination of this age and the 10 meter displacement of Qanat line of shafts byDasht-e Bayaz fault provide a slip rate of 5. 2-4. 3 mm/yr for this fault.