New kinematic constraints of the western Doruneh fault, northeastern Iran, from interseismic deformation analysis

Giuseppe Pezzo,Olivier Bellier,Cristiano Tolomei,Esmaeil Shabanian,Simone Atzori,Stefano Salvi,Yassaman Farbod

doi:10.1111/j.1365-246x.2012.05509.x

Abstract

We used the SBAS DInSAR analysis technique to estimate the interseismic deformation along the western part of the Doruneh fault system (DFS), northeastern Iran. We processed 90 ENVISAT images from four different frames from ascending and descending orbits. Three of the ground velocity maps show a significant interseismic signal. Using a simple dislocation approach we model 2-D velocity profiles concerning three InSAR data set relative to the western part of the DFS, obtaining a good fit to the observations. The resulting model indicates that a slip rate of ∼5 mm yr−1 accumulates on the fault below 10 km depth, and that in its western sector the Doruneh fault is not purely strike-slip (left-lateral) as in its central part, but shows a significant thrust component. Based on published geological observations, and assuming that all interseismic deformation is recovered with a single event, we can estimate a characteristic recurrence interval between 630 and 1400 yr.

Highlights

AND TECTONIC FRAMEWORKThe Doruneh fault system (DFS) is one of the longest and more prominent faults in Iran (Wellman 1966; Farbod et al 2011)
It is probably not possible to find an area completely devoid of tectonic deformation in Central Iran, because we are interested in the interseismic deformation accumulating along the Doruneh fault, we first estimated the ramps using velocities located at least 30–40 km from the western fault zone (WFZ) trace
According to our modelling procedure, the WFZ fault plane is constrained by the InSAR observations to be north-dipping, with dip values in the interval 60 ± 11◦ and that for a locking depth of 12 km, the most probable slip rates are 5 ± 1 mm yr−1

Summary

INTRODUCTION

The Doruneh fault system (DFS) is one of the longest and more prominent faults in Iran (Wellman 1966; Farbod et al 2011). The available geodetic data for northeastern Iran (Vernant et al 2004; Reilinger et al 2006) show a ∼7 mm yr−1 shear rate between the Lut block, south of the DFS and Eurasia (Figs 1a and b). The amount of deformation accumulated on the DFS, as well as the characteristics of its release, are not yet clear, given the scarcity of geodetic, geomorphologic and palaeoseismic data For this reason the knowledge of the seismotectonics of the fault, is rather limited. Few moderate (Mw 5–5.8) instrumental earthquakes have been recorded around the entire DFS, whereas the historical record shows no more than one event possibly associated to the DFS Such low seismicity might be either because of the lack of historical data or to long recurrence intervals for the largest earthquakes (Ambraseys & Melville 1982; Fattahi et al 2007; Farbod et al 2011). C 2012 The Authors, GJI, 190, 622–628 Geophysical Journal International C 2012 RAS

MULTITEMPORAL INSAR DATA A NA LY S I S

INTERSEISMIC DEFORMATION MODELLING

DISCUSSION AND CONCLUSION