Strike‐slip kinematics in Central and Eastern Iran: Estimating fault slip‐rates averaged over the Holocene

Abstract

According to GPS measurements, the right‐lateral shear between Central Iran and Afghan blocks amounts to 16 mm/yr. A model based on very long‐term estimates of fault‐rates suggests the current shear originated about 5 Ma ago and has been accommodated by strike‐slip faulting limited to the western (∼2 mm/yr, Gowk‐Nayband fault) and eastern (∼14 mm/yr, Sistan system fault) edges of the Lut block. We have used high‐resolution SPOT5 (pixel size 2.5 m) images to measure recent cumulative offsets and estimate slip‐rates over shorter time periods that average several seismic cycles only. Recent offsets, a few tens of meters, have been found along the Anar fault inside the Central Iran plateau and along the Sistan faults east of the Lut. The offset‐morphologies postdate the last incision of the network and are most probably of Holocene age (12 ± 2 ka). The corresponding slip‐rates range between ∼0.5–0.75 mm/yr, ∼1.75–2.5 mm/yr, ∼1–5 mm/yr, ∼1–2.5 mm/yr for the Anar, East Neh, West Neh, and Asagie fault, respectively. These estimates suggest the GPS shear‐rate across the Lut may not extrapolate over the Holocene. They also indicate strike‐slip faulting is not confined to the Lut edges, but also occurs in Central Iran, suggesting the ongoing strike‐slip tectonics might have originated between 8 and 22 Ma ago, earlier than considered previously and consistent with observations in NE Iran.