A. Kaveh Firouz; H. Nazari; M. Arian; A. Shafei; T. Majidi; M. Shokri
Abstract
The North Tehran Fault with a length of about 110 km in North of Tehran and soutern of central Alborz with W-E trend (N25˚E) and dipping (30˚NE) is located in western of Mosha Fault.The branch of Chitgar such as Milad and Vardavard Fault in the form of propagation fault is increased toward south. Previous ...
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The North Tehran Fault with a length of about 110 km in North of Tehran and soutern of central Alborz with W-E trend (N25˚E) and dipping (30˚NE) is located in western of Mosha Fault.The branch of Chitgar such as Milad and Vardavard Fault in the form of propagation fault is increased toward south. Previous morphotectonical investigation along the North Tehran Fault show that shear of quaternary sedimentation and pressure mechanism with left-lateral component. Determination of seismic parameter and seismic action that result of this fault movement, need to doing paleoseismological investigation. In this text with using stratigraphy correlation method, estimated of subsidence rate is 0.16 mm/yr and logging with ratio and ortho photography method, 3-6 event is determined with 6.4-7.4 magnitude and recurrence
A. Sistanipour; M. Pourkermani; M. Arian
Abstract
Bafq-Baghin fault system has formed by 8 fault segments. On this fault system has not recorded any historical seismic data. Instrumentally earthquakes are located in low depth and their magnitude is from small to medium. Morphometric parameters and the presence of fault scarp along the fault segments ...
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Bafq-Baghin fault system has formed by 8 fault segments. On this fault system has not recorded any historical seismic data. Instrumentally earthquakes are located in low depth and their magnitude is from small to medium. Morphometric parameters and the presence of fault scarp along the fault segments indicate their activeness. Recent earthquake epicenters of the region (2005-2009) have northeast-southwest trend are located at the intersection of southeast of the Bafq-Baghin fault system. Field investigations and satellite images of region show that the concentration trend of recent earthquake epicenters is located on the cross fault trend that introduced as Rafsanjan-Zarand fault. This fault is one of the X faults in the region that has formed by movement of shear zone.
A. Keynezhad; M. Pourkermani; M. Arian; A. Saeedi; M. Lotfi
Abstract
Detailed geological and structural analysis of north of Torud-Moalleman area (Central Iran), between Anjilu fault in north and Torud fault in the south, led to tectonic elements of this limit such as fractures and relative of their mechanism with left lateral sheared zone of two main faults. This study ...
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Detailed geological and structural analysis of north of Torud-Moalleman area (Central Iran), between Anjilu fault in north and Torud fault in the south, led to tectonic elements of this limit such as fractures and relative of their mechanism with left lateral sheared zone of two main faults. This study provides a movement system of Chalu, Gandi and Hafez faults in this shear zone. On the basis of kinematics findings and using general methods of fault slip analysis (orientation of slip plane, slip vector, shape of stress ellipsoid and angle of internal friction) region stress field were calculated after determining the angle of internal friction for each one of fault limits. Then, the main stress orientation determinates for combination data that values of ،وwere 195/10, 339/78 and 104/07 respectively. The shape of stress ellipsoid was defined on the basis of shape factor, [R= (-) / (-)], (Angelier, 1975). The R-value for whole studied regions was about 0.5 and deformation type was mainly left lateral transpressional with reverse component. Such results are evident from N-NE (N195) trending in the region and northward movement of the lithosphere. These finding are in line with field research results of fractures, faults and mechanism in this general shear zone.
V. Hosseini toudeshki; M. Pourkermani; M. Arian; Kh. Khosrotehrani
Abstract
Rivers are the most important landforms on the ground whose analysis is known as a useful tool in tectonic surveys in several thousands to two million years ago. The Ghezel Ozan River, the longest river system in the country, has responded to tectonic deformation thoroughly. Detection and characterization ...
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Rivers are the most important landforms on the ground whose analysis is known as a useful tool in tectonic surveys in several thousands to two million years ago. The Ghezel Ozan River, the longest river system in the country, has responded to tectonic deformation thoroughly. Detection and characterization of geomorphic anomalies in the Ghezel Ozan River and correlation with structures can specify the role of structures in making active deformations. The intense and sudden deflection in the river course, the abnormal changes in the river sinuosity and knick points upon longitudinal profile of the river are the geomorphic anomalies connected to the structures. Deflection of the river course and abnormal changes in the river sinuosity are identified on the satellite images and approved through field observations. Knick points are specified upon longitudinal profiles of the river and the effects of lithology are surveyed in making of them٫ so that only knick points are considered which are produced by structures. Longitudinal profiles of the river have been obtained from digital elevation model. Above mentioned anomalies then have been correlated with structures extracted from geology maps and in this manner structures effective in making geomorphic anomalies have been identified. The study region is located in Sanandaj – Sirjan, Centeral Iran and Western Alborz zones. Around the Ghezel Ozan River, marl, sandstone, siltstone, limestone, tuff, agglomerate and volcanic rocks are extremely exposed. These rocks belong to Qom, Upper Red, Lower Red and karaj formations. Deflection of the Ghezel Ozan River is surveyed in the regions of Kuh-e-Palangi, Jelovdarlou, Cham and Yengejeh. Abnormal changes in river sinuosity is studied in regions of Jomaelou, Gol gheshlagh, Armoutlou, Kuh-e-Qaravol, Ghaflankuh and Kuh-e-Pajdar. In the regions of Sharif Abad, Iemir, Kuh-e-Qaravol and Kuh-e-Pajdar, knick points are specified upon longitudinal profile of the Ghezel Ozan River. The obtained results show that folds with trends of NW – SE and NE – SW have the highest influence on deflection of the course of the Ghezel Ozan River. The other geomorphic anomalies produced by faults with trends of NW–SE , NE – SW, N-S and E-W especially in instances that faults with trends of NW – SE and NE – SW have intersected. Thus, the most active structural trends in around of the Ghezel Ozan River are trends of NW–SE, NE – SW, N-S and E-W which correlate with trends of fractures in basement of Iran. In this way active folds and faults are identified in the area.
Z. Mardani; M. Ghorashi; M. Arian; Kh. Khosrotehrani
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.This ...
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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 particulary 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), and index of mountain front sinuosity (Smf),we used an overall index(Iat) that is a combination of the other indices that divides the landscape into four classes of relative tectonic activity. The moderat class of Iat is mainly in the south of Manjel dam,while the rest of the study area has high active tectonics (shahrud drainage basin and sefidrud drainage basin),and high to very high(Taleghan and Alamut drainage basin). The stream network asymmetry (T)was also studied using morphometric measures of Tranverse Topographic Symmetry.Analysis of the drainage basins and subbasins in the study area results in a field of T-vectors that defines anomalous zone of the basin asymmetry.Acomparsion of T index clearly coincide with the values and classes of active tectonics indices and the overall Iat index.
M. Abdideh; M. Qorashi; K. Rangzan; M. Aryan
Abstract
This paper present a new method for evaluating relative active tectonics based on morphometric indices useful in evaluating morphology and topography. Indices used include: Bifurcation ratio (BR), Basin Relief (Bh), Drainage Density (DD), Ruggedness number (Rn), Stream frequency (Fu), Form Factor (FF), ...
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This paper present a new method for evaluating relative active tectonics based on morphometric indices useful in evaluating morphology and topography. Indices used include: Bifurcation ratio (BR), Basin Relief (Bh), Drainage Density (DD), Ruggedness number (Rn), Stream frequency (Fu), Form Factor (FF), Shape Factor (Ll), Sinuosity (Sl) and Elongation ratio (Re) of drainage basin. Results from the analysis are accumulated and expressed as an index of relative active tectonics, which we divide to from relatively low to highest tectonic activity. The study area in the central Zagros fold – thrust belt of the south western Iran is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than river system or mountain front. The study area has variable rates of active tectonics resulting from the collision between the continental Arabian plate and the so – called Iranian block belonging to Eurasia that has produced linear NW – SE anticline forms and thrusts. We test the hypothesis that areas of known, relatively high rates of active tectonics are associated with indicative value index of relative active tectonics.
R. Khavari; M. Ghorashi; M. Arian; Kh. Khosrotehrani
Abstract
The paper presents a method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height ...
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The paper presents a method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography. 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 analysis are accumulated and expressed as an index of relative active tectonics (Iat), which divided into four classes from relatively low to highest tectonic activity. The study area along the south flank of the central Alborz mountain range in north Iran is 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. The recent investigations show that neotectonism has played a key role in the geomorphic evolution of this part of the Alborz mountain range. Geomorphic indices indicate the presence of differential uplifting in the geological past. The high class values (low tectonic activity) for Iat mainly occur in the south and southeast of the Karaj drainage basin, while the rest of the study area has classes of Iat suggesting moderate to high tectonic activity. Around the Amirkabir Lake, Iat has the highest value. The distribution of the indices defines areas associated with different mountain fronts and estimates of relative rates of tectonic activity. More than half of the study area is classified into classes 2 or 1 of high to very high tectonic activity in terms of the apparent geomorphic response. In different tectonic environments with greater rates of active tectonics, the values of indices would differ as well as their range in value. The stream network asymmetry (T) was also studied using morphometric measures of Transverse Topographic Symmetry. Analysis of the drainage basin and a number of sub-basins in the study area results in a field of T-vectors that defines anomalous zones of the basin asymmetry. We test the hypothesis that areas with great stream migration are associated with indicatives values of Iat.
