Tectonics
Rojan Hemati; Manouchehr Ghorashi; Ali Solgi; Abdollah Saidi
Abstract
The Zagros suture zone is one of Key regions. Continent - Continent collision between Arabian plate and Iranian Block. This region is coincided by High Zagros and Zagros Simply Fold Zones in Western side and in other side is the Sanandaj- Sirjan Zone. The region of this research in situated in Northern ...
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The Zagros suture zone is one of Key regions. Continent - Continent collision between Arabian plate and Iranian Block. This region is coincided by High Zagros and Zagros Simply Fold Zones in Western side and in other side is the Sanandaj- Sirjan Zone. The region of this research in situated in Northern part of suture zone. The Zagros suture is oriented parallel to the other collision Structures as passive and active margins of Neo- Tethys Basin and also to Magmatic Arc (Urmiyeh - Dokhtar Arc).The main Faults in this region which we can mention by name are Zagros Main Thrust Fault and Zagros Main Recent Fault, Which they are also parallel to others structures. This region of suture zone in highly deformed and structures as folds, faults and nappes are the evident of a long compression Tectonics. The aim of this research firstly is analysing of folds and secondly is calculation of shortening rate of crust in this part of collision Zone. Three structural section (Eslam Abad- e- Gharb - Mahidasht, Kamyaran and Gazorkhani) have been balanced and the rate of shortening which is obtained respectively is 6252m , 6530m and 2040m.
Tectonics
Zeynab Taslimi; Abdollah Saidi; Mehran Arian; A. Solgi; Manouchehr Ghoreshi
Abstract
The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin ...
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The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin of Palo Tethys and Neotethys and it caused the complexity of abundant structural in other way too. The aim of this research is to investigate and analysis of existence structures in east central Alborz from northwest of Damghan (South of Toyeh) to South of Sari (North Alborz fault). The Structural features Analysis indicate that the Alborz Mountains are a fold and thrust belt. During the intense shortening of Alborz crust in the studied area the initial model of folds have been modified or destroyed. Some of these folds could take place in flexural flow folds or Drug folds classes since one limb of folds on the surface of low-angel thrust faults was thrusted recumbently. The thrust faults with south and north dipping is the main controller for variety structures in this part of Alborz. Based on geological and structural properties, construction of folding structures initiated during the Alpine orogeny since the late Eocene (37 million years) and the most shortening and faulting had occurred during at the Late Miocene. Data presented here demonstrate that shortening percent in the study area of Alborz Mountains is about 36.27% and the Rate of Shortening is estimated about 0.93 mm/y.
Tectonics
Tahmoores Yousefi; Kouros Yazdjerdi; Manouchehr Ghorashi; Alireza Shahidi
Abstract
The current form of the folded Zagros is the result of the oblique collision the Arabian and Iranian plates in Late Cenozoic. In this study, Cenozoic stress field changes in Zagros Simply folded belt and structural evolution after collision in Shiraz Area have been evaluated. The geological formations ...
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The current form of the folded Zagros is the result of the oblique collision the Arabian and Iranian plates in Late Cenozoic. In this study, Cenozoic stress field changes in Zagros Simply folded belt and structural evolution after collision in Shiraz Area have been evaluated. The geological formations under investigation are from Late Cretaceous to Neogene (Late Cenozoic). In this regard, geometry and kinematics of the faults, stylolites and other tectonic and stratigraphic evidence in geological formations outcrops in the study area at 30 stations were taken. The tension main axes (σ1, σ2, σ3) were calculated by Inversion Method for the categorized data. The results of the reconstruction of the paleo stress show compressional and Strike- Slip tectonic regime in Cenozoic. Moreover, anticlockwise rotation of the direction of compressive stress over time is about 60 degrees. As pre-folding compressional stress direction (σ1) is about N60E and its time is Miocene and before that. Whereas syn-folding stress direction is N35E and its age is equivalent to Pliocene that is the same age as old Bakhtiary formation. Stress changes in post-folding indicate N20E and its age equivalent to Pleistocene that is the same age as young Bakhtiary formation. At the present time, the maximum stress direction that is about N-S affects the area.
Tectonics
Tahmoores Yousefi; Kooros Yazdjerdi; 2Manouchehr Ghorash; Alireza Shahidi
Abstract
Abstract: The brittle tectonic history expresses different tectonic events in the Zagros Simply Folded Belt. Consequence of Mesozoic extension, rifting and the shortening derived from the Cenozoic Eurasia – Arabia collision. In order to reconstruction the ancient tensions in the Mesozoic deposits ...
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Abstract: The brittle tectonic history expresses different tectonic events in the Zagros Simply Folded Belt. Consequence of Mesozoic extension, rifting and the shortening derived from the Cenozoic Eurasia – Arabia collision. In order to reconstruction the ancient tensions in the Mesozoic deposits in the east and south-east of Shiraz, geometry and kinematics of the faults data simultaneously with sedimentation was investigated using the inversion method, to evaluated rifting time, the former of Neo-Tethys and its collisions in Cretaceous and Paleocene. In this regard 21 stations have been exposed in Khanekat to Pabdeh Formations. The resulted geometry and kinematics of the faults data were calculated situation main tension axes (σ1, σ2, σ3 ), tension ellipsoid figure or ratio of difference (ɸ). The results are as follows: from Triassic to upper Cretaceous (Mastrichtian) in Khanekat,Surmeh, Fahlian, Darian, Sarvak, Ilam, Gurpi, Tarbur Formations and Ghorban Member; extensional tectonic regime was dominant and having NE-SW direction (N052°) but in Pabdeh Formation with Paleocene age, tectonic regime has changed into compression with NE-SW compressional stress direction(N045°). So it was concluded that in simply folded Zagros of interior Fars, time of rifting and the forming of Neo-Tethyan basin was Triassic or older (Permian) with NE-SW extensional direction. The beginning of compressional tectonic regime with the same direction has been in Paleocene.
M. Talebian; M. Ghorashi; E. Kosari
Abstract
On 1-12 December 2017 three earthquakes (Mw 5.9 -6.1) shake Hojedk region in Kerman province. We used satellite images, radar interferometry and field investigation to examine the sourceprocesses of these earthquakes in south–central Iran. The epicenter of first two events located near northern ...
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On 1-12 December 2017 three earthquakes (Mw 5.9 -6.1) shake Hojedk region in Kerman province. We used satellite images, radar interferometry and field investigation to examine the sourceprocesses of these earthquakes in south–central Iran. The epicenter of first two events located near northern boundary of the Miankuh, a major topographic feature of the region. No surface rupture has been seen with these events and InSAR results show semi symmetric uplift of the region. Therefore, two scenarios of faulting with dip to the SW or NE are possible. Epicenter of the third event located further north within the alluvial plane. Evidence for coseismic surface rupture associated with this event was first observed on Sentinel satellite image and InSAR analysis. It was then confirmed by field investigation. The event produced a coseismic scarps with more than 1 m vertical displacement over a total distance of∼6 km, along a fault with reverse mechanism and dip to the SW. Any signs of earlier coseismic ruptures along this fault had been obliterated by the time of the 2017 earthquake, probably by occasional flash floods, so that the fault could not been identified beforehand. However, there is evidence of young alluvial offsets further to the NW along strike of the fault, suggesting existence of active structures in the region. Reactivation of blind faults have caused other major earthquakes such as 1978 Mw 7.4 Tabas, 2003 Mw 6.6 Bam, and 2017 Mw 7.3 Sarpol Zahab earthquakes in the past. The Hojedk earthquakes remind us about importance of recognizing and studying blind faults, especially if they are close to population centers.
Tectonics
Mohamad Reza Sajadian; Manouchehr Ghorashi; Elahe Javadi Mosavi; Mohsen Pourkermani; Mehran Arian
Volume 28, Issue 110 , December 2018, , Pages 299-306
Abstract
Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculate from ArcGIS and remote sensing packages over large area as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics. ...
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Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculate from ArcGIS and remote sensing packages over large area as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics. This is particularly valuable in west-central Alborz where relatively little work on active tectonics based on this method was done, so this method is new and useful. Based upon values of the stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), index of mountain front sinuosity (Smf) and transverse topographic symmetry factor (T), we used an overall index (Iat) that is a combination of the other indices. The low class of Iat are mainly in the sub-basins no; 6, 10,13,14,21,22,23,24,28 and the rest of the study area has moderate tectonic activities in the other sub-basins. Our results show that he moderate value has located along faulted area, which shows 2 class of relative tectonic activity.
H. Amiranlou; M. Pourkermani; R. Dabiri; M. Qoreshi; S. Bouzari
Abstract
The occurrence of historical and instrumental earthquakes near the North Tabriz Fault in NW Iran is an evidence for seismic activity of this fault, which recorded historical earthquakes with magnitudes greater than 7. In this study, existing experimental relations, historical seismicity, and the fault ...
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The occurrence of historical and instrumental earthquakes near the North Tabriz Fault in NW Iran is an evidence for seismic activity of this fault, which recorded historical earthquakes with magnitudes greater than 7. In this study, existing experimental relations, historical seismicity, and the fault geometry were used to define a Mw 7.7 earthquake scenario. The stochastic finite fault modeling based on a dynamic corner frequency shows a good agreement between maximum estimated acceleration and common attenuation patterns. The derived shake map illustrates that the stongest ground motion is observed in the NW, N and NE of the tabriz city along a zone parallel to the fault. In addition, the maximum acceleration derived from simulation is almost equal to that computed from attenuation patterns.
K. Nezhadafzali; R. Lak; M. Ghoreshi
Abstract
Mud volcano is a natural and spectacular phenomenon that usually appear in form of a dome but some are found as a basin. Mud volcanoes comprise a mixture of water, gas and mud. They are found in most parts of the world, particularly in the Alps and Himalayas belts. In Iran, most of the mud volcanoes ...
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Mud volcano is a natural and spectacular phenomenon that usually appear in form of a dome but some are found as a basin. Mud volcanoes comprise a mixture of water, gas and mud. They are found in most parts of the world, particularly in the Alps and Himalayas belts. In Iran, most of the mud volcanoes appear in coastal plains of the Caspian and Oman Seas. Mud volcanoes are known as indicators of oil and gas resources, and they are used to predict the existence of oil and gas reservoirs in Earth subsurface. The Napag mud volcano, as the largest and most active one in Iran, is located on the northern coast of the Oman Sea and is an interesting natural occurrence in the country. It is associated with a 39-m-high cone-shaped hill and several active and inactive vents. Mud eruption with different rates occurs usually every 3-5 minutes, and flows out from the western disrupted side of the edifice downslope toward the surrounding plain. In this research, a sediment sample was taken from the mud-flow during the field work, then analyses was analyzed for major, accessory and trace elements using ICP-OES machine in the laboratory. In addition, an analysis of the grain size of the sediment sample was carried out and the data were processed by the SPSS software. Results show that the sediment particles are of clay and silt in size. Al and Fe elements constitute 89.8 and 4.4 % of the sediment, and their high frequency is related to the high percentage of clay in the sediment. The evolution of the Napag mud volcano was investigated in three different stages: (1) Explosive, (2) Effusive (fast eruption with high rate), (3) Extrusive (slow and gradual eruption of material with high viscosity).
R Sadeghi; A Saidi; M Arian; M Ghorashii
Abstract
In this study, separation of paleostress phases in the Khalkhal region has been doneusing paleostress analysis based on heterogeneous fault slip data and related slip lineations.The data have been measured and collected from the Jurassic, Cretaceous and Eocene units.To determine the sense of shear or ...
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In this study, separation of paleostress phases in the Khalkhal region has been doneusing paleostress analysis based on heterogeneous fault slip data and related slip lineations.The data have been measured and collected from the Jurassic, Cretaceous and Eocene units.To determine the sense of shear or slip, indices such as stratigraphic separation across the faults, kinematic indicators on fault surfaces, conjugate fractures, and tensile cracks were used.The data were analyzed with the help of inversion method. The results indicate that strike-slip regime is dominant in the region. Constraining the stress phases and comparison with the field and seismic data revealed that the third stress regime is characterized by avertical σ2and a NE-SW extension related to the modern stress regime, which is also compatible with the seismic data. The first and second phases of stress prevailed along NW-SE and N-S directions related to the paleostress regimes.Various investigations, including rose diagram analysis of faults and arrangement of structures show that the faults in the region are dominantly strike-slip and strike-slip with normal component, and the shape of the stress field in the region is prolate.
Z Tashakkori; M Ghorashi; M Pourkermani
Abstract
The Kopet Dagh zone has been an area interest for geologists due to its sedimentary and structural similarities to the Zagros zone. In this study, the Jozek-Ghetlish main fault is introduced using the results of field studies, remote sensing, stratigraphic changes and seismic activities. The studies ...
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The Kopet Dagh zone has been an area interest for geologists due to its sedimentary and structural similarities to the Zagros zone. In this study, the Jozek-Ghetlish main fault is introduced using the results of field studies, remote sensing, stratigraphic changes and seismic activities. The studies show that in terms of seismicity, the earthquakes of August 1943 (Ms 7.6) and February 1976 (Ms 4.3) are the most important events recorded on this fault. From stratigraphy point of view, the facies changes from Shoorijeh formation to Zard formation from east to west is the most obvious stratigraphic change across the fault. Thickness variation (Isopach) maps of the Shoorijeh formation also show that its sickness decreases westward to zero adjacent to the fault, where the Zard formation thickens in the same direction. Deflected and offset stream channels across the southern part of the fault indicate a sinistral displacement along it. The streams draining the Yemendagh mountains in south of Ashkhane are deflected westward across the fault, and some of them show offsets of about 60 to 130 meters. In addition, in the northern part near the reservoir of Shirin Dareh dam, the axis of the syncline supporting the dam reservoir represents a sinistral displacement in the Aytamir sandstones. Further to NE, also, fold axis displacements in the Amirabad syncline, the Miyansoo anticline and even the Gifan syncline are other indications of the left-lateral motion along the fault. According to the NE-SW trend of the fault, its sinistral mechanism, and its effect on the tectonic zonation of this region, the Jozek-Ghetlish fault can be considered as the structural boundary between the eastern and western Kopet Dagh. Also, based upon stratigraphic thickness and facies variations across the fault (Zard and Shoorijeh formation), it can be a key to understand the Kopet Dagh oil reservoirs.
K Nezhadafzali; S Shayn; R Lak; M Yamani; M Ghorashi
Abstract
Mud volcano is a natural and attractive phenomenonwhich is generally found as a dome-like feature and basin-shaped in some cases. Mud volcanoes comprise mixtures of water, mud and gas. They are found in most parts of the world particularly in the Alps and Himalaya belts. In Iran, most of the mud volcanoes ...
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Mud volcano is a natural and attractive phenomenonwhich is generally found as a dome-like feature and basin-shaped in some cases. Mud volcanoes comprise mixtures of water, mud and gas. They are found in most parts of the world particularly in the Alps and Himalaya belts. In Iran, most of the mud volcanoes appear in the coastal plains of the Caspian and Oman seas. Mud volcanoes are commonly considered as indicating presence of oil and gas reserves, and are used to predict subsurface hydrocarbon fields. One or two mud volcanoes were formerly found between Minab and Jask in the Hormozgan Province. Remote sensing study followed by a field work of 30 days in this research led, for the first time, to the identification of 15 mud volcanoes in the Hormozgan Province using clustering analysis. During the field study, a sediment sample was taken from each mud volcano, which was then geochemically analyzed by ICP-OES. In the meantime, grain size was also determinedfor each sample. The SPSS software was used to process the data.After determining correlation coefficients, clustering analysis,and relationship between different factors obtained from Scuter plot, it turned out that AL, Fe, Ni, V, Sc, Ti, Cr, Zn, CU, Mn, Na, K, Li and Be in the mud volcanoes aregeogenic/continentalin origin, while the source of Ca,Mn and S is marine/intra-basinal and biogenic.
M Shayanfar; M Ghorashi; S.J Ahmadi; A Saeedi; A.R Shahidi
Abstract
The existence of a sedimentary basin with a large thickness of Neogene sediments(Lower Red Formation) in the Anarak-Talmessi region of central Iran with a basement of Precambrian metamorphic rocks, high rate of erosion processes, and more importantly its safety necessity led us to define the structural ...
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The existence of a sedimentary basin with a large thickness of Neogene sediments(Lower Red Formation) in the Anarak-Talmessi region of central Iran with a basement of Precambrian metamorphic rocks, high rate of erosion processes, and more importantly its safety necessity led us to define the structural pattern and analyze its active tectonics and seimotectonics. In this regard, field observations, processing of satellite images, and investigation of eroded landforms were used. According to the lack of Qom and Upper Red Formations and faulting plus aseismic characteristics of the area up to a radial distance of 86 km, it can be concluded that a combination of a stair-step uplift-erosion system has controlled the basin, which caused its scarp shape and lack of younger sediments.
N Saboor; M.R Ghassemi; M Eskandari; A Nazari.F; M Ghorashi; F Seenaian
Abstract
Depending on their structural maturity, seismogenic faults, , may rupture in one segment or as multiple segments; they also may show different slips on their segments. Mature faults break in long ruptures with small slip, while immature faults rupture as short segments but are more energetic. On the ...
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Depending on their structural maturity, seismogenic faults, , may rupture in one segment or as multiple segments; they also may show different slips on their segments. Mature faults break in long ruptures with small slip, while immature faults rupture as short segments but are more energetic. On the other hand, the mature faults demonstrate clustering pattern in their earthquake recurrence pattern. Also, the ground motions produced by earthquakes on immature faults are larger than those generated by earthquakes on mature faults. In this paper, we defined maturity of major faults in EasternIranseismotectonicProvince, considering their segmentation, rupture length, displacement vector on the rupture and the history of clustered earthquake sequence on the fault. Then, the response spectrum of ground motions caused by large earthquakes occurred on these faults were calculated. To reduce the effect of unknown wave paths, we used ground motions recorded in the near field. Earthquakes of different mechanisms were selected in magnitude range from Mw=5.7 to 7.1. We compared the obtained response spectrum with those resulted from the experimental model presented by Boore et al. (1997). Study of this parameter can help to recognized ground motion potenial of the faults, and considering it in extracting attenuation equations increases the accuracy of the results for seismic hazard assessment. Using our evaluation for structural maturity of the faults, we try to present a model for evolution of seismic activity in Eastern Iran.
M Nazemi; M Qurashi; M.R Ghassemi; M Arian
Abstract
Geomorphic characteristics of alluvial fans on the sides of the ShotoriMountains in east of Tabas represent two different groups . The first group is older and is more dominant with their heads near the ShotoriMountains' hillside and their toe spreading to the central parts of the plain. These alluvial ...
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Geomorphic characteristics of alluvial fans on the sides of the ShotoriMountains in east of Tabas represent two different groups . The first group is older and is more dominant with their heads near the ShotoriMountains' hillside and their toe spreading to the central parts of the plain. These alluvial fans on which no main recent channel sedimentation is occurring, are often consisted of old alluvial sediments with a thin cover of newer ones. The second group includes younger and active alluvial fans consisted of more recent sediments of stream bed, which are located at the termination of the first group or at the southern foothills of the ShotoriMountains. It can be said that in the first group, recent active sedimentation process by the main channel has been transferred to the lower parts and toe of the alluvial fan, but in the latter group sedimentation has been done on top of the alluvial fan and on older sediments. In other words, the first group consists of two obvious old and active (recent) parts, while the second group only includes recent and active alluvial fans. Our investigations indictaes that geomorphic pattern of these two alluvial fan groups has a clear relation with location and mechanism of active faults and geomorphic surfaces in the plain of Tabas and eastern slopes of the Shotori Mountains; in other words, it is related to the mechanism of structural evolution of this mountain. According to this pattern, wherever there is the active fault of the catastrophic 1978 earthquake at the front of mountain along which the ShotoriMountains are being uplifted, the second type of alluvial fans is formed. Where the fault is located in central parts of the plain as a result of deformational front propagation, and the old part of the alluvial fan and mountain are being uplifted along it, the first type of alluvial fans (with two separate parts) is formed. This uplift is accommodated by active faulting and folding associated with bedding plane faulting. Migration of deformational front during geologic evolution of the ShotoriMountains has caused four different geomorphic levels along with three generations of alluvial fans. It is concluded that investigating on geomorphic pattern of alluvial fans will provide valuable data about the location of active Quaternary faults in alluvial plains. This pattern shows an active fault near Boshruyeh (east of the ShotoriMountains). Although no major earthquake has been reported from the fault, all morphotectonic evidences show its activity and thus the occurrence of large earthquakes in the future is expected.
J Ehsani; M Arian; M Ghorashi
Abstract
This paper aims at evaluating relative active tectonics in the Jarahi-Hendijan drainage basin based on geomorphic indices. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage ...
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This paper aims at evaluating relative active tectonics in the Jarahi-Hendijan drainage basin based on geomorphic indices. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf). Results from the analyses were combined to achieve an index of relative active tectonics (Iat), which is divided into four classes implying relatively low to very high tectonic activity. The study area is located across the Zagros Mountains belt (high Zagros, folded belt, and frontal lowlands) in southwest Iran, and comprises an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than a single valley or mountain front. Recent investigations show that neotectonism has played a key role in the geomorphic evolution of this part of the Zagros ranges. Geomorphic indices indicate the presence of differential uplifting in the geological past. Higher values of Iat (low tectonic activity) mainly occur in the southwest of the Jarahi- Hendijan drainage basin, while the rest of the study area falls into classes of Iat that indicate moderate to high tectonic activity. Baghmalek and Takhtderaz sub-basins show the highest values of relative tectonic activity. The distribution of this index defines areas associated with different faults and relative rates of tectonic activity. Nearly 40% of the study area is classified into Classes 1 and 2 implying very high to high tectonic activity, and 37% is grouped as Class 4, which is taken to indicate low tectonic activity. Areas of higher relative tectonic activity represent lower Iat values.
M Haj Manuchehri; M Arian; M Ghorashi; A Solgi; A Sorbi
Abstract
Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculated from ArcGIS and Remote Sensing software packages over large areas as a reconnaissance tool to identify possible geomorphic anomalies related to active ...
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Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculated from ArcGIS and Remote Sensing software packages over large areas as a reconnaissance tool to identify possible geomorphic anomalies related to active tectonics. This method is particularly new and useful in areas where relatively little work has been carried out on active tectonics based on this method. Based upon the values of stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf), we used an integrated index (Iat) that is a combination of the other indices. This index divides the landscape into four classes of relative tectonic activity. According to the Iat results, sub-basins 4 and 6 show zones of low tectonics activity (Class 4), sub-basins 1, 2, 7, 9, 10, 11, 12, 14, 15 and 19 fit to areas of moderate tectonic activity (Class 3), and high tectonic activity is represented by sub-basins 3, 5, 8, 13, 16, 17 and 18 (Class 2). The Tranverse Topographic Symmetry (T) was also studied using morphometric measurements, which finally gave a plot of T-vectors defining anomalous zones of basin asymmetry. A comparison between T index and map of relative tectonic activity showed a consistent coincidence between areas of higher Iat classes with zones of greater asymmetry.
N Bagha; M Ghorashi; M Arian; M Pourkermani; A Solgi
Abstract
Structural development, caused by active tectonics leads to deformation of morphology features. The Mosha-North Tehran fault zone, located in south edge of the Central Alborz consists of significant tectonic structures. Hence, study on morphotectonic signs is a proper method for evaluation of relative ...
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Structural development, caused by active tectonics leads to deformation of morphology features. The Mosha-North Tehran fault zone, located in south edge of the Central Alborz consists of significant tectonic structures. Hence, study on morphotectonic signs is a proper method for evaluation of relative tectonic activities in the area. In this research, six main morphometric indices such as stream length-gradient (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height(Vf), drainage basin shape (Bs), and mountain front sinuosity(Smf)were considered. The computations and probes of these indices indicate three classes of relative tectonic activity in the study area from low to high level. Consequently, the drainage basins with high class of tectonic activity mostly coincide with the main faults in south edge of the Central Alborz.
S Bahiraee; M Arian; M Qorashi; A Solgi
Abstract
The Mosha fault is the most important fault structures in the south of Central Alborz. According to the activity of this fault, confirmation of the morphological evidences, and large historical earthquakes occurred by its activity, also proximity to Tehran metropolitan, the study of this area is very ...
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The Mosha fault is the most important fault structures in the south of Central Alborz. According to the activity of this fault, confirmation of the morphological evidences, and large historical earthquakes occurred by its activity, also proximity to Tehran metropolitan, the study of this area is very important. Therefore, as a parameter, evaluation of the fault movement potential helps us in seismological study of the area. In this paper, we have used the model presented by Lee et al. (1997) to evaluate movement potential. The model is based on the relationship between fault geometrical characteristics and regional tectonic stress field. To use the equations of this model, structural data of 13 stations along the Mosha fault were collected to identify the position of the principal axes of stress. Then, we obtained the direction of maximum principal stress of the Mosha fault and also for each section separately by using Inversion method and they were placed in equations.
H Alizadeh; M Aryan; M Lotfi; M Ghorashi; M Ghorbani
Abstract
The Dehaj-Sardoiyeh Belt, which is a part of the Urmia-Dokhtar Volcanic-Plutonic Zone, consists of several economic porphyry copper deposits. This area is located on the right lateral shear zone surrounded by the Rafsanjan fault in the north and the Shahr-e Babak fault in the south. In this research, ...
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The Dehaj-Sardoiyeh Belt, which is a part of the Urmia-Dokhtar Volcanic-Plutonic Zone, consists of several economic porphyry copper deposits. This area is located on the right lateral shear zone surrounded by the Rafsanjan fault in the north and the Shahr-e Babak fault in the south. In this research, spatial relationship among sixteen porphyry copper deposits, faults and fractures was studied. The results show a strong relationship between the Photo lineament factor and location of the porphyry copper deposits. The direction of lineament factor (d/D) was found to be highly correlated with the location of porphyry deposits. The results can be used in exploring preliminary porphyry deposits with regard to the geometry and mechanisms of the faults and fractures.
S Alimardan; Sh Solaymani Azad; M Ghorashi; M.R Ghorashi; B Oveisi; A Hatami
Abstract
Due to urban population growth in recent decades and the need for decentralization of cities with limited facilities and increasing marginalization in the larger cities, construction of new cities around large towns has been considered by decision makers to develop a plan to create new cities around ...
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Due to urban population growth in recent decades and the need for decentralization of cities with limited facilities and increasing marginalization in the larger cities, construction of new cities around large towns has been considered by decision makers to develop a plan to create new cities around these towns. One of the most important parameters for the construction of new population centers is seismotectonic studies. Hashtgerd New Town in southern slopes of the Alborz (located 65 km northwest of Tehran) is located on the uplifted deposits of the Plio-Quaternary. Vertical tectonic movements in the range caused the height difference of about 300 m between Hashtgerd and its southern plain elevations. Due to the emplacement of the city on the uplifted Plio-Quaternary deposits, and the lack of information about the causative active fault in this region, an attempt has been made to investigate the morphotectonic characteristics of the area on the basis of survey satellite image, aerial photo, digital elevation model, and field observations. In the present study, an active fault zones with NW-SE trends has been identified with oblique-slip movements (compression with left-lateral strike-slip component). The N-NE stress direction, in regards to the abovementioned trend is oblique, and hence, the result could be a transpressional regime for the area. Recognition of mentioned active faults is very important for earthquake hazard assessment studies for the new town.
A Shafiei Bafti; M Pourkermani; M Arian; M ghorashi
Abstract
One of the most important tools of recognition for uplifting Movements in an area is study of rivers. The Davaran Mountain Range, which situated between Zarand and Rafsanjan cities, is limited by the Jorjafk fault in the north face. This fault is 160 km long and divided into two northern and southern ...
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One of the most important tools of recognition for uplifting Movements in an area is study of rivers. The Davaran Mountain Range, which situated between Zarand and Rafsanjan cities, is limited by the Jorjafk fault in the north face. This fault is 160 km long and divided into two northern and southern parts. The north part is in the northern margin of Davaran Mountain Range and 100 km long. The southern part is an intra-mountain fault and 60 km long. In the northern part, thrust faulting of the pre-Neogene rock units over the Neogene-quaternary sediments shows the recent activity movements of this fault, although there is no record of historical and instrumental seismicity of the Jorjafk fault. For investigation of uplifting movements caused by this fault, we studied the morphotectonics of rivers limited to this fault. According to our studies, the sinuosity rates for 21 rivers calculated and gave mean ratio of 1.11. The mean ratio of SL index for 15 major rivers is 165.6. The V index shows less than 1 value for 7 rivers. The long profiles of 7 rivers prepared and all show the concave profiles with the minor dome in their long. The minor dome caused by the lithological variations in floor of the rivers. The greatest concaving belongs to river no 5. Our studies show the moderate uplifting values in central part of the Jorjafk fault, near the Hosen village. The uplifting movements show a reduction from the central to the end point of this fault.
M Foroutan; H Nazari; B Meyer; M Sébrier; M Fattahi; K Le Dortz; M Ghorashi; Kh Hessami; M. R Ghassemi; M Talebian
Abstract
The Dehshir fault system (DFS) including six fault segments forms the western border of NS-striking active dextral strike-slip fault cutting the Sanandaj-Sirjan, Uromieh-Dokhtar magmatic arc, and Central Iran. This active fault system right-laterally offset Eocene volcanic rocks and Quaternary alluvial ...
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The Dehshir fault system (DFS) including six fault segments forms the western border of NS-striking active dextral strike-slip fault cutting the Sanandaj-Sirjan, Uromieh-Dokhtar magmatic arc, and Central Iran. This active fault system right-laterally offset Eocene volcanic rocks and Quaternary alluvial fans. Geomorphic evidence imply the activity of the DFS in the Late Quaternary, and paleoseismic investigations revealed seismic movements along the Marvast fault segment during the Late Pleistocene and Holocene timescales. In order to unravel the seismic history of the DFS over the intermediate geologic (103 -105 yr) time scale, and based on the morphotectonics and sedimentary-stratigraphic properties, three paleoseismic sites have been selected along the 35-km-long stretch of the Marvast fault segment. The southern site (Harabarjan) shows steep fault branches of N140±10º strike with sub-horizontal striations in dextral component. Another trench has been excavated at the North Marvast site whitin the Late Pleistocene-Holocene alluvial and colluvial deposits. OSL analysis of loose quartz rich deposits yielded an age of ~72 ka for the oldest exposed sediments. Paleoseismic stduies along the Marvast fault segment provide evidence for the occurrence of several large seismic events associated with surface ruptures along the DFS. The chronology of paleoearthquakes on the Marvast segment indicates that at least 7 large (≈Mw > 7) earthquakes occurred in the last 43 ka with an average recurrence time of 3650±150 years. The most recent earthquake, event I, occurred ~2200 years ago, which associated with 2-4 m of dextral slip and >40 km surface rupture along the Marvast fault segment. These investigations are compatible with the lack of destruction in the Marvast historical (~1300 years) castle, located
M Royatvand; A Bahroudi; M. Qoreshi; M. R. Ghasemi; S. A. Aghahosseini
Abstract
The Oligocene salt in the Garmsar and Eyvankey plateau, south–central Alborz, has extruded on the quaternary sediments and formed a salt glacier. This open-toe salt glacier is about 24×17 km that is unique continental salt glacier in the world, dimensionally. Also, this ductile substrate ...
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The Oligocene salt in the Garmsar and Eyvankey plateau, south–central Alborz, has extruded on the quaternary sediments and formed a salt glacier. This open-toe salt glacier is about 24×17 km that is unique continental salt glacier in the world, dimensionally. Also, this ductile substrate has affected on structural styles of this region. However, little systematic work has done on it. To investigate the structural styles of the region that affected by a ductile substrate and adjacent region with a frictional decollement, and also the structures of the salt glacier,series of models were done which were scaled sandbox models. These sandbox models simulated the propagation of deformation of thin-skinned simultaneous shortening above adjacent ductile and frictional of two end member of decollement. Model results illustrate that above a ductile substrate, deformation propagates further and more rapidly than above a frictional substrate as we can see in the nature that the region with a ductile substrate is so broader than the adjacent region with a frictional decollement. Like the models, toward the north in the nature where the Decollement is frictional, from North Tehran Fault as a frontal fault to Mosha and Kandovan Faults in the core of Alborz Mountain, the dip of the faults are increased and only forward-vergent imbricate faults, whereas above the ductile substrate the dip of faults has not a definite pattern of dip and also, both foreland and hinterland imbricate faults develop.
M. Basiri; H. Nazari; M. Foroutan; S. Solaymani Azad; M. A. Shokri; M. Talebian; M. Ghorashi; M. J. Bolourchi; A. Rashidi
Abstract
The Golbaf area in Kerman province (SE Iran) has experienced five earthquake of Mw 5.4-7.1 between 1981 and 1998. Occurrences of these earthquakes in seventeen years time interval indicate that occurrences of earthquakes on the Golbaf (Gowk) fault system have a clustering model. In this study we use ...
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The Golbaf area in Kerman province (SE Iran) has experienced five earthquake of Mw 5.4-7.1 between 1981 and 1998. Occurrences of these earthquakes in seventeen years time interval indicate that occurrences of earthquakes on the Golbaf (Gowk) fault system have a clustering model. In this study we use morphotectonical and paleoseismological evidences to show that seismic behavior of this fault in the past has a clustering model in some time intervals. For this purpose at the first near-field morphotectonical analysis performed using real time kinematics (RTK) GPS survey and digital elevation model and digital topographic map of surface ruptures of past earthquake prepared with high accuracy. Detail analyzing of this model indicate that the rake angle of Golbaf fault is about 10 degree. This result is in agreement with rake angle calculated from seismological methods and also observations of slickenlines on rupture plans that show dominant right lateral strike slip mechanism of the Golbaf fault. According to the paleoseismological investigations which were associated with digging a trench perpendicular to the Golbaf fault indentified four Paleoearthquake with magnitudes of Mw>6.6. By using some of empirical relationship, maximum magnitude of oldest Paleoearthquake calculated about Mw 8.2 that it is unbelievable and show similar to today that occurred five earthquake during short time interval on this fault, occurrence of earthquake in the past on some of time interval have clustering model so that occurred a lot of big earthquake in short time interval that there was not enough opportunity for sedimentation and record of evidences of this earthquake separately.
A. Fathian Baneh; S. Solaymani Azad; H. Nazari; M. Ghorashi; M. Talebian
Abstract
Tabriz city, the most highly population city of NW Iran, is located close to the North Tabriz Fault (NTF). This 150 km right-lateral strike-slip fault consists of two major fault segments arranged in right-stepping pattern. A pull-apart basin has been formed within the overlap zone of these fault segments ...
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Tabriz city, the most highly population city of NW Iran, is located close to the North Tabriz Fault (NTF). This 150 km right-lateral strike-slip fault consists of two major fault segments arranged in right-stepping pattern. A pull-apart basin has been formed within the overlap zone of these fault segments due to the recent right-lateral motion. The basin margins mark by fault branches and fault splays, which connect these two major segments of NTF. High level historical earthquakes occurrence shows seismic activity of NTF. Among which, NTF is responsible of at least two destructive earthquakes occurred in 1721 A.D. (Ms 7.3) and 1780 A.D. (Ms 7.4). This fault has not experienced any strong seismic events since 1780 A.D. Within past decades, it has been tried to recognize large number of old earthquakes utilizing paleoseismological investigation. Previous paleoseismological studies have been focused on the NW and SE segments of the fault. In the present study, to complete the data sets necessary to assess the seismic hazard related to Tabriz city, we focus on overlap zone of the two main fault segments. Using aerial photos, satellite images and field investigations, a potential site has been recognized within the zone (6 km NW of Tabriz City) to perform paleoseismological studies. Trench opened perpendicular to fault scarp strike and focused paleoseismological investigations in that, show evidences of at least two macroseismic events.