Constant Slip Rate on the Doruneh Strike‐Slip Fault, Iran, Averaged Over Late Pleistocene, Holocene, and Decadal Timescales

Abstract

Varying estimates of both present-day strain accumulation and long-term slip-rate on the Doruneh left-lateral strike-slip fault, NE Iran, have led to suggestions that it exhibits large along-strike and/or temporal changes in activity. In this paper, we make and compare estimates of slip-rate measured using both geodesy and geomorphology, and spanning time periods ranging from decadal to 100 ka. To image the present-day accumulation of strain we process seven years (2003-2010) of data from six ENVISAT tracks covering the fault, with interferograms produced for 400 km-long strips of data in order to image the long-wavelength signals associated with interseismic strain accumulation across the locked fault. Our analysis shows that less than 4 mm/yr -and likely only 1-3 mm/yr -of slip accumulates across the fault.Using high-resolution optical satellite imagery we make reconstructions of displacement across six alluvial fans whose surfaces cross the fault, in four separate river catchments. We determine the ages of these fans using infra-red-stimulated luminescence dating combined with U-series dating of pedogenic carbonates. The six fans vary in age from ~10-100 kyr, and a regression line fitted to four of these yields a slip rate of 2.5 ± 0.3 mm/yr. We conclude that within the uncertainty of our measurements the slip-rate has remained constant over the last ~100 ka and is representative of the strain accumulation at the present-day. The slip-rate that we measure is consistent with the E-W left-lateral Doruneh fault accommodating N-S rightlateral faulting by 'bookshelf' faulting, with clockwise rotation about a vertical axis.

Interseismic Strain Accumulation Across the Main Recent Fault, SW Iran, From Sentinel‐1 InSAR Observations

“…Iran is generally a suitable target location for InSAR, given its relatively arid climate and sparse vegetation cover. InSAR time series methods have been applied to measure interseismic slip rates on a number of faults in the region, including the Ashkabad (5–12 mm/yr; Walters et al., 2013), Doruneh (2.5 ± 0.3 mm/yr; Mousavi et al., 2021), North Tabriz (6–10 mm/yr; Aghajany et al., 2017; Karimzadeh et al., 2013; Rizza et al., 2013; Su et al., 2016), Shahroud (4.75 ± 0.8 mm/yr; Mousavi et al., 2015), and the Minab‐Zendan‐Palami (10 mm/yr) and Sabzevaran‐Kahnuj‐Jiroft (7.4 mm/yr) fault systems (Peyret et al., 2009). However, InSAR has not previously been used to estimate the interseismic motion across the MRF, despite the potential of this technique to better constrain both the slip rate and locking depth of this important fault.…”

Interseismic Strain Accumulation across the Main Recent Fault, SW Iran, from Sentinel-1 InSAR Observations

“…Iran is generally a suitable target location for InSAR, given its relatively arid climate and sparse vegetation cover. InSAR time series methods have been applied to measure interseismic slip rates on a number of faults in the region, including the Ashkabad (5-12 mm/ yr; Walters et al, 2013), Doruneh (2.5 ± 0.3 mm/yr; Mousavi et al, 2021), North Tabriz (6-10 mm/yr; Aghajany et al, 2017;Karimzadeh et al, 2013;Rizza et al, 2013;Su et al, 2016), Shahroud (4.75 ± 0.8 mm/yr; Mousavi et al, 2015), and the Minab-Zendan-Palami (10 mm/yr) and Sabzevaran-Kahnuj-Jiroft (7.4 mm/yr) fault systems (Peyret et al, 2009). However, InSAR has not previously been used to estimate the interseismic motion across the MRF, despite the potential of this technique to better constrain both the slip rate and locking depth of this important fault.…”