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Transient Aseismic Slip Following 2017 Mw 7.3 Sarpol-e Zahab, Iran, Earthquake: Possible Evidence for Fault Frictional Heterogeneity and Thin-skinned Shortening Following a Thick-skinned Basement-involved Faulting in the Zagros Fold-thrust Belt
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  • Zelong Guo,
  • Mahdi Motagh,
  • Jyr-Ching Hu,
  • Guangyu Xu,
  • Mahmud Haghshenas Haghighi,
  • Abbas Bahroudi,
  • Aram Fathian
Zelong Guo
GFZ German Research Centre for Geosciences

Corresponding Author:[email protected]

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Mahdi Motagh
GFZ German Research Center for Geosciences
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Jyr-Ching Hu
National Taiwan University
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Guangyu Xu
East China University of Technology
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Mahmud Haghshenas Haghighi
Leibniz University Hannover
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Abbas Bahroudi
University of Tehran
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Aram Fathian
RWTH Aachen University
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We use interferometric synthetic aperture radar (InSAR) observations to investigate the fault model and afterslip evolution within 3 years after the 2017 Sarpol-e Zahab, Iran, Mw 7.3 earthquake. The anti-listric fault which is very similar to flat-and-ramp structure inverted by kinematic afterslip models is proposed to simulate the coseismic slip and afterslip evolution. Compared with listric faults, linear inversions demonstrate that a planar fault can explain coseismic deformation well enough. However, the stress perturbations caused by this basement-involved faulting propagated upward to the sedimentary cover. The transition of sedimentary cover-basement interface inferred by afterslip models is at the depth of ~13 km in the seismogenic zone, which coincides with the regional stratigraphic profile and indicates that the significant afterslip updip of the coseismic rupture is mainly controlled by frictional property. We additionally find the postseismic deformation is dominated by afterslip while the viscoelastic response is negligible with the best-fitting viscosity which is on the order of 1019Pa s. Compared to the best-fitting kinematic afterslip model, the stress-driven afterslip model tends to underestimate early postseismic deformation to the west, which may indicate the spatial heterogeneity of the frictional property of fault plane. Because the coseismic rupture propagated along a basement-involved fault while the postseismic slip was likely to activate the frontal structures and/or shallower detachments in the sedimentary cover, the 2017 Sarpol-e Zahab earthquake may act as a typical event which contributes to both of the thick- and thin-skinned shortening of the Zagros in both seismic and aseismic way.