Active strike-slip faulting in the Zagros Mountains: Geological and geomorphological evidence of the pull-apart Zaribar Lake basin, Zagros, NW Iran

On 7 November 2019 (22:47 UTC) a Mw 5.9 earthquake struck the East-Azerbaijan region, in the north-western Iran, about 100 km east of Tabriz, the fourth largest city of Iran with a population of over two million. This seismic event caused both widespread damage to the surrounding villages and casualties, killing about 5 people and injuring hundreds. The occurrence of this earthquake is related to the main geodynamic regime controlled by the oblique Arabia-Eurasia convergence and, in particular, this event is inserted in the tectonic context of the East-Azerbaijan Plateau, a complex mountain belt that contains internal major fold-and-thrust belts.In this work, we first generate the coseismic deformation maps by applying the Differential Synthetic Aperture Radar Interferometry (DInSAR) technique to SAR data collected along ascending and descending orbits by the Sentinel-1 constellation of the European Copernicus Programme. Then, we invert them through analytical modeling in order to better constrain the geometry and characteristics of the main source. The retrieved fault model revealed a shallow seismic source approximately NE&#8211;SW-striking and characterized by a left-lateral strike-slip, southeast-dipping faulting mechanism. Our retrieved solution reveals a new minor fault never mapped in geological maps before, whose kinematics is compatible with that of the surrounding structures and with the local and regional stress states.&#160;Moreover, we also use the preferred fault model to calculate the Coulomb Failure Function at the nearby receiver faults; taking into account the surrounding geological structures reported in literature, we show that all the considered receiver faults have been positively stressed by the main event. This is also confirmed by the distribution of the aftershocks that occurred near the considered faults.&#160;The analysis of the earthquake nucleated along these left-lateral strike-slip minor fault is essential to improve our knowledge of the East-Azerbaijan Plateau; therefore, further studies are required to evaluate their role in seismic hazard definition of northwest of Iran, in order to help in the mitigation of the seismic hazard in seismogenic regions unprepared for the occurrence of seismic events.This work is supported by: the 2019-2021 IREA-CNR and Italian Civil Protection Department agreement, H2020 EPOS-SP (GA 871121), ENVRI-FAIR (GA 824068) projects, and the I-AMICA (PONa3_00363) project.

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Spatial evolution of Zagros collision zone in Kurdistan, NW Iran: constraints on Arabia–Eurasia oblique convergence

Solid Earth ◽

10.5194/se-7-659-2016 ◽

2016 ◽

Vol 7 (2) ◽

pp. 659-672 ◽

Cited By ~ 19

Author(s):

Shahriar Sadeghi ◽

Ali Yassaghi

Keyword(s):

Late Cretaceous ◽

Strike Slip ◽

Suture Zone ◽

Fault System ◽

Spatial Evolution ◽

Nw Iran ◽

Collision Zone ◽

Deformation Partitioning ◽

Oblique Convergence ◽

External Part

Abstract. Stratigraphy, detailed structural mapping and a crustal-scale cross section across the NW Zagros collision zone provide constraints on the spatial evolution of oblique convergence of the Arabian and Eurasian plates since the Late Cretaceous. The Zagros collision zone in NW Iran consists of the internal Sanandaj–Sirjan, Gaveh Rud and Ophiolite zones and the external Bisotoun, Radiolarite and High Zagros zones. The Main Zagros Thrust is the major structure of the Zagros suture zone. Two stages of oblique deformation are recognized in the external part of the NW Zagros in Iran. In the early stage, coexisting dextral strike-slip and reverse dominated domains in the Radiolarite zone developed in response to deformation partitioning due to oblique convergence. Dextral-reverse faults in the Bisotoun zone are also compatible with oblique convergence. In the late stage, deformation partitioning occurred during southeastward propagation of the Zagros orogeny towards its foreland resulting in synchronous development of orogen-parallel strike-slip and thrust faults. It is proposed that the first stage was related to Late Cretaceous oblique obduction, while the second stage resulted from Cenozoic collision. The Cenozoic orogen-parallel strike-slip component of Zagros oblique convergence is not confined to the Zagros suture zone (Main Recent Fault) but also occurred in the external part (Marekhil–Ravansar fault system). Thus, it is proposed that oblique convergence of Arabian and Eurasian plates in Zagros collision zone initiated with oblique obduction in the Late Cretaceous followed by oblique collision in the late Tertiary, consistent with global plate reconstructions.

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Neotectonics of the Avaj region (NW Iran): left-lateral strike-slip and range-parallel reverse faults

Journal of Mountain Science ◽

10.1007/s11629-019-5688-0 ◽

2020 ◽

Vol 17 (4) ◽

pp. 838-850

Author(s):

Reza Alipoor ◽

Amir Hossein Sadr ◽

Sahar Ghamarian

Keyword(s):

Strike Slip ◽

Lateral Strike Slip ◽

Nw Iran

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Extension and slip rate partitioning in NW Iran constrained by GPS measurements

Journal of Geodetic Science ◽

10.2478/v10156-011-0008-9 ◽

2011 ◽

Vol 1 (4) ◽

pp. 286-304 ◽

Cited By ~ 2

Author(s):

A. Rastbood ◽

B. Voosoghi

Keyword(s):

Large Scale ◽

Slip Rate ◽

Strike Slip ◽

Fault System ◽

Arabian Plate ◽

Normal Faults ◽

Gps Data ◽

Gps Measurements ◽

Nw Iran ◽

Himalayan Mountain

Extension and slip rate partitioning in NW Iran constrained by GPS measurementsConvergence of 22±2 mm yr-1 between the northward motion of the Arabian Plate relative to Eurasia at N8° ±5° E is accommodated by a combination of thrust and strike-slip faults in different parts of Iran. Dislocation modeling is used to examine the GPS data for this part of the Alpine-Himalayan mountain belt with more concentration in NW Iran. First, the vectors due to known Arabia-Eurasia rotation are reproduced by introducing structures that approximate the large-scale tectonics of the Middle East. Observed features of the smaller scale fault system are then progressively included in the model. Slip rate amplitudes and directions adjusted to fit available GPS data. Geological evidences show strike-slip and reverse-slip faulting in NW Iran, but GPS data show normal faults in this region too. By slip partitioning we propose four locations for normal faults based on extensions observed by GPS data. Slip rate values were estimated between 2 ~ 5 mm/yr for proposed normal faults. Our modeling results prove that the NW Iran is not only affected by Arabia-Eurasia collision but also contributes in the subduction motion of the South Caspian and Kura basins basement beneath the Apsheron-Balkhan sill and the Great Caucasus respectively.

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Spatial evolution of Zagros collision zone in Kurdistan – NW Iran, constraints for Arabia–Eurasia oblique convergence

Solid Earth Discussions ◽

10.5194/sed-7-2735-2015 ◽

2015 ◽

Vol 7 (3) ◽

pp. 2735-2773 ◽

Cited By ~ 2

Author(s):

S. Sadeghi ◽

A. Yassaghi

Keyword(s):

Late Cretaceous ◽

Early Stage ◽

Strike Slip ◽

Suture Zone ◽

Fault System ◽

Spatial Evolution ◽

Nw Iran ◽

Collision Zone ◽

Oblique Convergence ◽

Synchronous Development

Abstract. Stratigraphy, detailed structural mapping and crustal scale cross section of the NW Zagros collision zone evolved during convergence of the Arabian and Eurasian plates were conducted to constrain the spatial evolution of the belt oblique convergence since Late Cretaceous. Zagros orogeny in NW Iran consists of the Sanandaj–Sirjan, Gaveh Rud and ophiolite zones as internal, and Bisotoun, Radiolarite and High Zagros zones as external parts. The Main Zagros Thrust is known as major structures of the Zagros suture zone. Two stages of deformation are recognized in the external parts of Zagros. In the early stage, presence of dextrally deformed domains beside the reversely deformed domains in the Radiolarite zone as well as dextral-reverse faults in both Bisotoun and Radiolarite zones demonstrates partitioning of the dextral transpression. In the late stage, southeastward propagation of the Zagros orogeny towards its foreland resulted in synchronous development of orogen-parallel strike-slip and pure thrust faults. It is proposed that the first stage related to the late Cretaceous oblique obduction, and the second stage is resulted from Cenozoic collision. Cenozoic orogen-parallel strike-slip component of Zagros oblique faulting is not confined to the Zagros suture zone (Main Recent) but also occurred in the more external part (Marekhil–Ravansar fault system). Thus, it is proposed that oblique convergence of Arabia–Eurasia plates occurred in Zagros collision zone since the Late Cretaceous.

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Evidence for distributed active strike-slip faulting in NW Iran: The Maragheh and Salmas fault zones

Tectonophysics ◽

10.1016/j.tecto.2018.05.022 ◽

2018 ◽

Vol 742-743 ◽

pp. 15-33 ◽

Cited By ~ 2

Author(s):

Karim Taghipour ◽

Mohammad Mahdi Khatib ◽

Mohmoudreza Heyhat ◽

Esmaeil Shabanian ◽

Abdorreza Vaezihir

Keyword(s):

Fault Zones ◽

Strike Slip ◽

Nw Iran

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Sedimentology and sediment geochemistry of the pelagic Paryab section (Zagros Mountains, Iran): implications for sea level fluctuations and paleoenvironments in the late Paleocene to middle Eocene

Arabian Journal of Geosciences ◽

10.1007/s12517-021-07291-0 ◽

2021 ◽

Vol 14 (11) ◽

Author(s):

Seyed Hamidreza Azami ◽

Michael Wagreich ◽

Maryam Mortazavi Mehrizi ◽

Mohamad Hosein Mahmudy Gharaie ◽

Susanne Gier ◽

...

Keyword(s):

Sea Level ◽

Middle Eocene ◽

Sediment Geochemistry ◽

Bivariate Analysis ◽

Zagros Mountains ◽

Statistical Parameters ◽

Nw Iran ◽

Depositional Processes ◽

Geochemical Parameters ◽

Pabdeh Formation

AbstractSedimentological and geochemical records are presented for an upper Paleocene to middle Eocene deep-water pelagic succession of the Pabdeh Formation in the Paryab section, Zagros Mountains, NW, Iran. In this study, grain-size statistical parameters, cumulative curves, and bivariate analysis on twenty-five sediment samples were used to decipher depositional processes and paleoenvironments. XRD analysis of the fine-grained silt to clay sediments indicates that quartz, calcite, ankerite/dolomite, and clay minerals such as illite, chlorite, and kaolinite constitute the main minerals within these sediments. Elemental and isotopic chemostratigraphies are used to infer depositional conditions and sea level trends through time. TOC-CaCO3 trends of the samples are used to interpret the type of deposition and sediment accumulation rates, rhythmic bedding, and identification of regressional and transgressional phases. In the studied section, the manganese contents exhibit a declining trend along the lowstand systems tract that terminates in a sea level lowstand and the subsequent start of a transgressive trend. Some geochemical parameters such as Mn values and δ13C contents of sediments along a sequence can be used as potential sea level proxies that are tested in this study. The Paleocene-Eocene Thermal Maximum (PETM) interval of the Pabdeh Formation coincides with increasing Mn contents and Mn/Al ratios. Ti/Al and Si/Al ratios show contrasting trends to Mn values and Mn/Al ratios. Generally, elemental and isotopic results of the Pabdeh Formation confirm the presence of a long-term three-stage sea level cycle in the studied interval that is related to the PETM event. Based on elemental analyses such as Co, Mo, Ni, V, and Cr contents, the Pabdeh Formation sediments were deposited in suboxic to slightly anoxic conditions.

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