R Razavi Pash; M.R Ghassemi; H Safari
Abstract
The study area is located in western Alborz range, and is part of the Lahijan sinistral strike-slip fault system. This area is observed as a depressed basin on the digital elevation model. This research uses field studies, remote sensing techniques and statistical methods to investigate and analyze geometry ...
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The study area is located in western Alborz range, and is part of the Lahijan sinistral strike-slip fault system. This area is observed as a depressed basin on the digital elevation model. This research uses field studies, remote sensing techniques and statistical methods to investigate and analyze geometry and kinematics of the faults in the Rostam-Abad area, and benefits structural and geomorphic evidences to introduce a pull-apart basin in the area. Our analysis indicates that the Rostam-Abad area is located in the overlap zone of two sinistral strike-slip fault segments of the Lahijan fault zone with a left-step array. Presence of frequent normal faults, extensional fractures, rhombic pattern of the depression, extensive alluvial deposits, and intrusion of igneous dykes in young sandstones within the Rostam-Abad depression also verify a local extensional tectonic regime in this region.
S Ansari; F Yaminifard; M Tatar
Abstract
In this study, 23 focal mechanisms were calculated by moment tensor inversion of small regionalـlocal earthquakes in the Western Alborz and surrounding areas using wave-form inversion method. Calculated reverse-fault focal mechanisms around the Khazar and Alborz Faults in the Central Alborz, considering ...
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In this study, 23 focal mechanisms were calculated by moment tensor inversion of small regionalـlocal earthquakes in the Western Alborz and surrounding areas using wave-form inversion method. Calculated reverse-fault focal mechanisms around the Khazar and Alborz Faults in the Central Alborz, considering southward-dipping nodal plane as the fault plane, are consistent with relatively low-angle thrusts. It also implies dominant compressionsl regime in the north of the Central Alborz. Focal mechanisms in 1990 Rudbar-Tarom Earthquake region show a combination of strike-slip mechanisms and a complex fault system in the middle of the Western Alborz. A major region of dominant strike-slip mechanisms is observed in the Talesh area, located in the west of the SouthCaspianBasin, and around the Masuleh, Sangavar and Bozqush faults. The only calculated focal mechanism close to the southern margin of the Western Alborz, considering the western part of the North Tehran fault as the fault nodal plane, implies leftـlateral motion in this area. In the south of the western AlborzMountains approaching the Central Iran, two calculated mechanisms indicate dominant reverse movement, similar to the 2002 Changoreh-Avaj Earthquake. Five focal solutions close to the Kushk-e Nosrat and Soltanieh Faults, considering these faults as the fault nodal planes, are consistent with right-lateral motion along them. Depth of the earthquakes in the studied region is in the range of 2 and 20 km, indicating the brittle upper crust in the region.
A Ghahramani Zakaria; H Nazari; M Pourkermani
Abstract
This research has been achieved with the purpose of morphotectonic studies of the Sufian-Shabestar fault zone in the West Alborz-Azerbaijan (NW Iran). The fault zone cuts the Neogene and Quaternary units in south of the MishoMountains. The maximum of horizontal and vertical displacements along the Sufian-Shabestar ...
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This research has been achieved with the purpose of morphotectonic studies of the Sufian-Shabestar fault zone in the West Alborz-Azerbaijan (NW Iran). The fault zone cuts the Neogene and Quaternary units in south of the MishoMountains. The maximum of horizontal and vertical displacements along the Sufian-Shabestar fault zone are H=2500±200 m in Meshnaq river and V=66±4 m in fan east of Benis village, respectively. The minimum of horizontal and vertical displacements along this fault are H=9±0/5 m in offset stream of N Sharafkhaneh city and V=6±4 m in river NW of Kozehkanan city, respectively, all estimated based on combining data of Digital Elevation Model in scale of 1/25000, aerial photographs in scale of 1/20000, LANDSAT ETM satellite imagery and field studies. The estimated rate of horizontal and vertical displacements are H=135±20 m V=19±4 m in NW of Sharafkhaneh city, respectively and all allow us to estimate the rake of fault by geometry calculations. Based on estimate, the rake of the Shabestar fault segment is 11±4W. The Sufian-Shabestar fault zone is a right lateral-reverse strike slip fault with strike N81E and rake range of between 04, 11 with westwards dip, all estimated based on the rake of fault plane and morphotectonic data. Therefore, the Sufian-Shabestar fault zone (including faults segments of Sufian, Shabestar, F1, Sharafkhaneh (F2) and F3) is neotectonically an active zone.
H Safari; M. R. Ghassemi; M. Agh- Atabay; R. Razavi pash
Abstract
Lahijan fault zone is one of the transverse faults in western Alborz which with, sinistral mechanism caused structural deformations in this region. In this research, with using of field investigations, Remote Sensing techniques and statistical structural analysis methods, the structural analysis of Lahijan ...
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Lahijan fault zone is one of the transverse faults in western Alborz which with, sinistral mechanism caused structural deformations in this region. In this research, with using of field investigations, Remote Sensing techniques and statistical structural analysis methods, the structural analysis of Lahijan fault zone is performed and consequently, the fault zone (Geometry) is constructed. On the basis of results of this research, the Lahijan fault with attitude N 55/70-SE has 30 Km width. This fault zone is considered as sinistral fault zones which have different related fractures. The fractures related fault zone are ordered as syntethic and Antithetic faults. Most of faults in this fault zone have Net- slip movements and the angle of these to main fault zone, specified their mechanisms so, the parallel faults zone have left- lateral movements and in opposite, the faults with angle of 75˚ related to fault zone trend, have Right- lateral movements. Due to progressive sinistral deformation, all of structures rotated counter- clockwise and placed in lesser angle relative to this shear zone.