How to reveal the present-day mechanism of the 600 km long Doruneh fault in eastern Iran ?

The enigmatic 600 km long E-W trending left-lateral Doruneh fault in eastern Iran is certified to be active by its well preserved geomorphological features all along its trace, but it is lacking recent seismic activity that could be attributed to its motion. Instead, the high seismogenic potential of the study zone is highlighted by the two M=7 earthquakes on the left-lateral E-W trending Dasht-e-Bayaz fault just south of Doruneh, in 1968 and 1979. Therefore, it remains important to understand the role of the Doruneh fault in the kinematics of the Arabia-Eurasia collision that takes place inside Iran’s political boundaries.

Many different slip-rates have been estimated for the left-lateral motion of the Doruneh fault: 2.5 mm/yr by geomorphological marker offset dating, 1 mm/yr from preliminary GNSS measurements, and 5 mm/yr from a local InSAR study.  These rather local estimates on the 600 km long fault highlight either temporal or spatial variability of the Doruneh present-day behavior. The spatial variability of the fault slip is still badly constraint as the western half of the fault is located in the Great Kavir desert. The analysis of satellite radar images was supposed to provide good constraints on the inter-seismic deformation with a full spatial coverage of the fault, especially thanks to the favorable E-W orientation of the Doruneh fault and the arid Iranian climate. However, decorrelation due to sand dunes and unexpected large tropospheric noise prohibited precise results from a first large-scale ENVISAT study, yielding an upper limit of the slip rate of 4 mm/yr. The high resolution SENTINEL-1 constellation (operational since 2014) is predicted to provide constraints on inter-seismic velocities down to 2 mm/yr from 2020 on. In complement, a dense GNSS survey has been conducted in 2012 and 2018 on a temporary network of 18 sites around a large part of the fault. This network densifies and completes the 17 permanent GNSS stations in up to 200 km distance to the fault trace situated mostly in the eastern, more populated part of the fault.

In this work, we will point out our recent GNSS, InSAR and tectonic studies on the present-day characteristics of the Doruneh fault, to better understand the mechanism of this major fault in the kinematics of the Arabia-Eurasia collision, and to contribute to a better assessment of the seismic hazard in eastern Iran.