Applying the OSL to determine the slip-rate of the Abr Fault

The Abr fault is one of the left-lateral strike-slip faults in the southeast of the Alborz Mountains. Previously, by means of Cosmogenic Nuclide dating (TCN- ages of boulders samples ۹۰-۱۰۰ ka), the cumulative displacement and the slip-rate of the fault were calculated as ۴۰۰ m and ۳-۴ mm yr-۱, respectively. We decided to employ OSL for determining the slip rate. To compare the OSL and TCN ages, we chose our sampling location close to the sampling location (the Q۳ unit) of Javidfakhr et al. (۲۰۱۱). However, the ages obtained from sediments using the OSL method were much younger (۲۲ ka) than the ages from boulders using the TCN method. This suggest that the layer which was used for OSL dating was created after the abandonment of the Q۳ unit, and possibly this layer exist in that region, and therefore, according to the new displacements of the region, which is about ۶۰ meters, the slip-rate has been calculated ۲.۷ mm yr-۱, which is slightly lower than the slip rate calculated by the TCN dating method (۳-۴ mm yr-۱).The OSL provides the age of a much younger layer.