Interseismic deformation of the Shahroud fault system (NE Iran) from space‐borne radar interferometry measurements

Abstract

The Shahroud fault system is a major active structure in the Alborz range of NE Iran whose slip rate is not well constrained despite its potential high seismic hazard. In order to constrain the slip rate of the eastern Shahroud fault zone, we use space‐borne synthetic aperture radar interferometry with both ascending and descending Envisat data to determine the rate of interseismic strain accumulation across the system. We invert the slip rate from surface velocity measurements using a half‐space elastic dislocation model. The modeling results are consistent with a left‐lateral slip rate of 4.75 ± 0.8 mm/yr on the Abr and Jajarm, strands of the Shahroud fault, with a 10 ± 4 km locking depth. This is in good agreement with the 4–6 mm/yr of left‐lateral displacement rate accumulated across the total Shahroud fault system obtained from GPS measurements.

The Post‐Eocene Evolution of the Doruneh Fault Region (Central Iran): The Intraplate Response to the Reorganization of the Arabia‐Eurasia Collision Zone

“…This convergence is mostly absorbed through contractional deformation along the Zagros and by distributed shortening in the north, within the Alborz and Kopeh Dagh Mountain ranges (Figure ). The obliquity of convergence with respect to the major tectonic boundaries has resulted in a combination of translation and shortening in the intracontinental domains (Authemayou et al, ; Calzolari, Della Seta, et al, ; Djamour et al, ; Ghods et al, ; Hollingsworth et al, ; Javidfakhr et al, ; Mousavi et al, ; Nozaem et al, ; Ritz et al, ; Rizza et al, ; Robert et al, ; Shabanian et al, , ; Shabanian, Bellier, et al, ; Shabanian, Siame, et al, ; Talebian & Jackson, ).…”

Slip‐Rate on the Main Köpetdag (Kopeh Dagh) Strike‐Slip Fault, Turkmenistan, and the Active Tectonics of the South Caspian

“…In this paper we use an updated GPS estimate of the Iran-Eurasia shortening, along with measurements of the strike-slip rates along the MKDF and SFZ, to estimate the amounts of South Caspian-Iran and South Caspian-Eurasia shortening, and to constrain the SCB motion relative to both Iran and Eurasia. in the eastern Alborz (Mousavi et al, 2015) and Köpetdag (this paper), to provide better constraint on the motion of the SCB relative to both Iran and Eurasia. The approach that we take in constructing our velocity triangle allows us to estimate the amount of shortening perpendicular to the eastern Alborz and Köpetdag, and thus the overall motion of the SCB.…”

“…We separate the relative motion of Iran and the South Caspian into strikeslip parallel to the eastern Alborz and a component of shortening perpendicular to the range. For the range-parallel strike-slip component we use the 4.8 ± 0.8 mm/yr obtained by Mousavi et al (2015) with InSAR, and a strike of 244°. The Shahrud Fault system (SF) is the main fault identified in the geomorphology and has comparable late Quaternary estimates of slip rate, such that we assume the strain accumulation is likely to be accommodated across this fault, as represented on Figure 11 by the green line (with thick error bar) extending WSW from the Iran vertex, with the gray shaded band allowing for the uncertainty in Iran-Eurasia motion.…”

“…These rates compare favorably with earlier estimates of SCB-Eurasia motion of 11 ± 2 mm/yr in direction 335° ± 5 and SCB-Iran motion of 7 ± 1 mm/yr in direction 225° The Iran-Eurasia motion is known from Khorrami et al (2019) and is 11.9 ± 0.4 mm/yr. The strike-slip component on the Shahrud Fault (SF) is 4.8 ± 0.8 mm/yr toward 244° (Mousavi et al, 2015), which is the green line (with thick error bar) extending WSW from the Iran vertex, with the shaded band allowing for the uncertainty in Iran-Eurasia motion. The strike-slip component on the Kopet Dag Fault (KF) is 9.1 ± 1.3 mm/ yr (this paper) toward 300°, which is the red line (with thick error bar) extending NW from the Eurasia vertex.…”

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

“…All rights reserved. Walpersdorf et al, 2014;Mousavi et al, 2015], and also of the Holocene and late Pleistocene slip-rates on many of its major active faults [e.g. Ritz et al, 2003;Regard et al, 2005;Fattahi et al, 2006;Rizza et al, 2011;Fattahi et al, 2014;Foroutan et al, 2014;Talebian et al, 2016].…”