We reveal transient surface deformation following the 2017 Mw7.3 Sarpol Zahab (Iran) earthquake using Interferometric Synthetic Aperture Radar (InSAR) measurements. Based on the coseismic ...interferograms derived from the Advanced Land Observing Satellite‐2 (ALOS‐2) data, the preferred slip model of the earthquake has a centroid depth of 14.5 ± 4 km and suggests that a basement fault is most likely responsible for the 2017 earthquake in the northwest Zagros fold‐thrust belt zone. Two slip asperities with a maximum slip of 6 m separated by 16 km are observed in the best fitting slip model. The accumulated afterslip in the first month after the mainshock determined from the Sentinel‐1 postseismic interferograms reveals a slip distribution that lies immediately updip of the coseismic slip, implying that frictional properties of the fault vary along the rupture patch. The Bamo Mount in the earthquake area was uplifted by approximately 1 m during the earthquake. We suggest that local topographic growth from both seismic and aseismic faulting behaviors is common within the Zagros fold‐thrust belt zone based on our findings regarding the 2017 earthquake and other significant events in the region.
Key Points
We propose that a basement fault at a depth of 15 km in the northwest Zagros folded belt zone is responsible for the strongest earthquake instrumentally recorded in the Iran‐Iraq border region, the 2017 Mw7.3 Sarpol Zahab earthquake
Two asperities with a maximum slip of 6 m in the 2017 Mw7.3 Sarpol Zahab earthquake were revealed with InSAR observations
Frictional properties of the earthquake fault vary in the rupture area
The oblique collision between the northeastern margin of the Arabian platform and the Iranian microcontinent has led to transpressional deformation in the Zagros orogenic belt in the central part of ...the Alpine–Himalayan orogenic belt. Although previous articles have emphasized the dextral sense of shear in the Zagros orogenic belt, in this paper, using several indicators of kinematic shear sense upon field checking and microscopic thin-section studies, evidence of the development of a sinistral top-to-the NW deformation belt is presented. The mean attitudes of the foliations and lineations in this belt are 318°/55°NE and 19°/113°, respectively.
A doublet earthquake event including two main shocks with a magnitude larger than Mw 6.0 occurred on 1 July 2022 in the Zagros fold‐and‐thrust belt, southeast Iran. The coseismic InSAR deformation ...field shows that this event caused significant surface uplift due to fault‐related folding in the seismic zone. The estimated preferred faulting model suggests that a higher dip angle fault (maximum slip of ∼1.1 m), and an overlying gentle dipping fault (maximum slip of ∼1.2 m) within the Bandar‐e‐Lengeh Anticline, are responsible for the first and second main shocks, respectively. The calculated Coulomb failure stress change suggests that the first main shock and its Mw 5.7 aftershock have a significantly positive triggering effect in the second main shock. The accumulated interseismic strain should have been partly released by the two main shocks. Finally, the salt diapir activity may affect the generation of the earthquake in the seismic zone.
Plain Language Summary
The doublet earthquake frequently occurred in the southeast part of the Zagros fold‐and‐thrust belt in the past years. In this study, we first adopted the Synthetic Aperture Radar images captured by Sentinel‐1 satellite to map the coseismic surface deformation of the 2022 Hormozgan doublet earthquake. The uplift of fault‐related folding controls the coseismic surface motion of these events from blind thrusting. Moreover, the two main shocks are caused by the rupture of two faults within the Bandar‐e‐Lengeh Anticline. Furthermore, the first main shock increased the stress in the source area of the second main shock, and positive triggered the rupture of the seismogenic fault of the second main shock. The interseismic surface deformation suggests that the 2022 Hormozgan doublet earthquake may have released the accumulated interseismic strain for the past ∼104 years. In addition, salt diapir activity in the southeast part of the seismic zone may contribute to the 2022 Hormozgan doublet earthquake.
Key Points
A doublet earthquake occurred in the southeastern of Zagros fold‐and‐thrust belt with a significant salt layers activity
A combination of steep and shallow blind faults is responsible for the 2022 Hormozgan doublet earthquake
The interseismic strain accumulation and salt diapir activity in the southeast of the seismic zone may cause this doublet earthquake
The temporal and spatial distribution of deformation during the early phases of Plateau formation is poorly known. The Iranian Plateau is developing in response to Arabia–Eurasia convergence and is a ...potential analog to the early phases of Tibetan Plateau deformation. Previous studies document the onset of the Iranian Plateau growth based on the kinematic history of the Zagros to the south and the Alborz Mountains to the north. Here we present new detrital apatite fission track (AFT) data from 13 modern rivers of the Talesh Mountains, northwestern Iranian Plateau. These mountains lie immediately south west of the rigid South Caspian Block. A total of 1233 single grain cooling ages were measured and range between 185 and 4Ma. Deconvolution of grain-age data documents three main phases of exhumation including: the Oligocene (30–23Ma), early to middle Miocene (18–12Ma), and early Pliocene (~5Ma). Comparison between cooling ages from the Talesh Mountains and elsewhere across the Iranian Plateau indicates widespread plateau formation in the Oligocene, earlier than previously suggested for the northwestern plateau margin. These results highlight deformation on both the northern and southern margins of the plateau over almost the entire history of Iranian Plateau formation. A similar pattern of synchronous deformation on the north-northeastern and southern margins of the Tibetan Plateau has recently been documented and highlights the significance of rigid basement blocks focusing far field deformation for both plateaus.
•AFT ages quantify at 3023, 18–12 and ~5Ma deformation phases in the Talesh Mts.•These deformation phases in the Talesh Mts. related to Arabia–Eurasia collision.•Iranian Plateau wide cooling ages quantify its formation and growth pattern.•Iranian and Tibetan plateaus experienced synchronous deformation at their margins.•Rigid blocks focused the far field stresses transferred from the collision zone.
The left‐lateral Doruneh Fault System (DFS) bounds the north margin of the Central Iranian microplate and has played an important role in the structural evolution of the Turkish‐Iranian plateau. The ...western termination of the DFS is a sinistral synthetic branch fault array that shows clear kinematic evidence of having undergone recent slip sense inversion from a dextral array to a sinistral array in the latest Neogene or earliest Quaternary. Similarly, kinematic evidence from the Anarak Metamorphic complex suggests that this complex initially developed at a transpressive left‐stepping termination of the DFS and that it was inverted in the latest Neogene to a transtensional fault termination. The recognition that the DFS and other faults in NE Iran were inverted from dextral to sinistral strike slip in the latest Neogene and the likely connection between the DFS and the Herat Fault of Afghanistan suggests that prior to the latest Miocene, all of the north Iranian and northern Afghan ranges were part of a distributed dextral fault network that extended from the west Himalayan syntaxes to the western Alborz. Also, the recognition that regional slip sense inversion occurred across northern and northeastern Iran after the latest Miocene invalidates tectonic models that extrapolate Pleistocene to recent fault slip kinematics and rates back beyond this time.
Key Points
The western termination of the DFS shows clear kinematic evidence of recent slip sense inversion
The DFS and other faults in NE Iran were inverted from dextral to sinistral in the latest Neogene
The tectonic reversal invalidates models that extrapolate recent fault kinematics before this time
Abstract
In this paper, geodetic leveling data in three lines across the Central Alborz range have been utilized to analyse recent activities of the range major faults. These data gathered by ...National Cartographic Center of Iran in three times during the past 22–32 yr. Mathematical modeling is applied to remove systematic errors from the raw leveling data. The vertical movement (uplift or subsidence) rate is estimated from height differences of benchmarks during geodetic leveling data times. The results show that the average uplift in Central Alborz during data times varies from 17.0 ± 0.9 to 18.1 ± 0.9 mm in the hangingwall of the major North Tehran and Mosha faults, respectively. The lower values of the uplift across the faults are taken as an account for the faults locking during the data times and their possible seismic potential. Evaluation of the uplift rate for the major faults under study in Central Alborz indicates the reduction of vertical uplift from west to east along the main proven faults like the Mosha Fault. The rate of uplift in the hangingwall of the Mosha Fault decreases from 0.921 ± 0.283 (mm yr−
1) (20.3 ± 0.905 mm 22 yr−1) in west to the rate of 0.508 ± 0.228 (mm yr−1) (11.7 ± 1.031 (mm 23 yr−1)) in east. The unusual subsidence anomalous in some benchmarks is considered as the effect of geological features such as Karst phenomena. Moreover, comparison on the rate of vertical movement across the Central Alborz shows the greater uplift in the southern flank (10.4 ± 0.9 mm) with respect to its northern flank (6.3 ± 0.9 mm) during the data times. This interpretation is in agreement with Global Positioning System studies that indicates a progress of young deformation in Central Alborz toward the range southern hillside.
A metamorphic core complex model is proposed for Khoshoumi Mountain uranium mineralization located in the Bafq–Saghand metallogenic zone of central Iran. Uranium mineralization occurred in the ...Chapedoni metamorphic complex. Detailed structural analysis of the complex leads to the interpretation that the mineralization is spatially concentrated in a low angle shear zone of mylonitized migmatite, the lower ductile part of the Chapedoni metamorphic complex. The shear zone that has top to the NE sense of shear in the northeastern and southeastern parts of the mountain and top to the WNW sense of shear in the southwestern part is a detachment zone to the Chapedoni Metamorphic Core Complex (CMCC). The Eocene granite is the plutonic core to the CMCC. The shear zone is cut by several NE‐trending left‐lateral strike‐slip faults. This later faulting is interpreted to account for the significant enrichment of uranium in the southern part of the mountain. The bimodal distribution of radiometric data gathered from exploratory drill holes in this part of the mountain constrains this interpretation. That is, the lower value is from the shear zone across the area but the higher value is from the places that the shear zone is cut by the transverse faults.
The Talesh Mountains at the NW margin of the Iranian Plateau curve around the southwestern corner of the South Caspian Block and developed in response to the collision of the Arabian‐Eurasian Plates. ...The timing, rates, and regional changes in late Cenozoic deformation of the Talesh Mountains are not fully understood. In this study, we integrate 23 new apatite and zircon bedrock U‐Th/He ages and structurally restored geologic cross sections with previously published detrital apatite fission track data to reconstruct the deformation history of the Talesh Mountains. Our results reveal that slow rock exhumation initiated during the late Oligocene (~27–23 Ma) and then accelerated in the middle Miocene (~12 Ma). These events resulted in the present‐day high‐elevation and curved geometry of the mountains. The spatial and temporal distribution of cooling ages suggest that the Oligocene bending of the Talesh Mountains was earlier than in the eastern Alborz, Kopeh Dagh, and central Alborz Mountains that initiated during the late Cenozoic. Late Oligocene and middle Miocene deformation episodes recorded in the Talesh Mountains can be related to the collisional phases of the Arabian and Eurasian Plates. The lower rate of exhumation recorded in the Talesh Mountains occurred during the initial soft collision of the Arabian‐Eurasian Plates in the late Oligocene. The accelerated exhumation that occurred during final collision since the middle Miocene resulted from collision of the harder continental margin.
Key Points
Late Cenozoic deformation in the Talesh Mountains initiated at late Oligocene (27–23 Ma) then accelerated during middle Miocene (12 Ma)
Bending of the Talesh Mountains around the South Caspian Block starting in the late Oligocene and accelerated during middle Miocene
Episodes of deformation recorded here for the Talesh Mountains attributed to the collisional phases of the Arabian and Eurasian Plates
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