L. Aghajari; S. A. Alavi; M. R. Ghassemi; M. A. Kavoosi
Abstract
Different geological, structural and morphological characteristics of the eastern Kopeh-Dagh Province in NE Iran resulted in identification of several morphotectonic domains separated by major basement faults. Based on various field surveys, seismic reflection data, satellite images and cross-sections ...
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Different geological, structural and morphological characteristics of the eastern Kopeh-Dagh Province in NE Iran resulted in identification of several morphotectonic domains separated by major basement faults. Based on various field surveys, seismic reflection data, satellite images and cross-sections construction we introduce the fault-bounded deformed areas with different characteristics as the structural domains. These domains are the Hezar-Masjed, Darreh-Gaz- Sarakhs, and the Kopeh-Dagh foredeep from southwest to northeast, respectively. They are bounded by the Kashafrud, Mozduran, and the North Kopeh-Dagh faults. The domains were formed on the Turan plate since Middle Jurassic times when the extensional phase commenced in the Kopeh-Dagh Province. The bounding faults were initially of normal mechanism which generated grabens and half-grabens within the sedimentary basin. The maximum extension and subsidence in the basin occurred during Middle Jurassic, synchronous with the deposition of the Kashafrud Formation. Differential subsidence and configuration of the basin resulted in lateral lithofacies variations and thickness changes of the Kashafrud Formation throughout the basin. The main compression event in the Kopeh-Dagh Province started following the closure of the Neo-tethys ocean between the Iranian and Arabian plates in the Late Eocene, which caused inversion tectonics and reactivation of pre-existing normal faults as well as folding of sedimentary cover.
B Taherkhani; H Nazari; M Pourkermani; M Arian
Abstract
The E-W trending North Qazvin Fault is situated in north & northeast of Qazvin city in south-central Alborz. Across the fault, Karaj formation (Eocene) is thrusted over Hezardarreh Formation (A) and the alluvial B Formation. It could be the source for the 1119 AD earthquake with an estimated magnitude ...
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The E-W trending North Qazvin Fault is situated in north & northeast of Qazvin city in south-central Alborz. Across the fault, Karaj formation (Eocene) is thrusted over Hezardarreh Formation (A) and the alluvial B Formation. It could be the source for the 1119 AD earthquake with an estimated magnitude of Ms: 6.5. The North Qazvin Fault is a seismically active fault, therefore it is one of the most important earthquake threats for the Qazvin as an industrial city of Iran. Morphotectonicand detailed field studies along a part of the North Qazvin Fault allows us to measure horizontal and vertical offsets caused by recent movements on this fault. One of the measured horizontal and vertical displacements due to the recent movements on the fault is 4 and 3.5 meters, respectively. The geometry (strike, dip and rake) of the North Qazvin Fault in this part is 090˚, 45˚, 51˚ respectively. Our investigations show that the North Qazvin Fault is a north-dipping compressional fault. The North Qazvin Fault and its surrounding faults such as Najm-abad fault appear as a propagating fault system which has left-lateral compressional kinematics in southern part of the west-central Alborz.
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.
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.
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.
M Sheban; F Ghaemy; A Abbasnejad; F Ghaemy
Abstract
Neotectonics that is a major factor of landform development in tectonically active regions has significantly affected fluvial systems and mountain-front landscapes in the Behabad area of the Central Iran Zone. To assess tectonic activities in the area, we analyzed geomorphic indices including the mountain-front ...
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Neotectonics that is a major factor of landform development in tectonically active regions has significantly affected fluvial systems and mountain-front landscapes in the Behabad area of the Central Iran Zone. To assess tectonic activities in the area, we analyzed geomorphic indices including the mountain-front sinuosity (Smf), stream-gradient index (SL), valley floor width–valley height ratio (Vf), drainage basin shape (Bs) and drainage basin asymmetry (Af). These indices were combined to yield the relative active tectonics indices (Iat). Based on Iat values, the study area was divided into four parts: Class 1 (very high relative tectonic activity, 1.52% in area), Class 2 (high, 68.58%), Class 3 (moderate, 20%), and Class 4 (low, 9.9%). The results are consistent with field observations on landforms and geology. The active tectonics indices and geomorphological evidences indicate that the tectonic activity rate in the studied area is predominantly moderate to high.
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.
M. Khademi
Abstract
The only geologic evidence of the neotectonic activity of theTorud region is its seismisity which assumed to be related to the Torud seismogenic fault. This fault has been overlain by the Quaternary alluvium in the major part of its length. Therefore, the study of morphotectonical characteristics of ...
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The only geologic evidence of the neotectonic activity of theTorud region is its seismisity which assumed to be related to the Torud seismogenic fault. This fault has been overlain by the Quaternary alluvium in the major part of its length. Therefore, the study of morphotectonical characteristics of the region gives more evidences about its activity. Calculation of three morphotectonic indices including stream length – gradient ( SL) and ratio of valley – floor width to valley height (Vf) of stream channels and mountain front sinuosity (Smf) shows high SL values (425 – 1044) and low Vf (2.68 – 3.34) and Smf (1.05 – 1.44) values and indicate that the region has activity specially at two parts: central part (near the mountain front ) and northwestern part ( near the main divide of the Torud mountains) and therefore the tectonic activity class of the region can be number 1. The activity of the central part can be due to the movements of the Torud fault. The activity of the northwestern part is the result of the uplift of the region which is related to the at least one fault parallel with the Torud fault that has formed the relic mountain fronts at recent past. The distribution of strain of this activity shows the progressive deformation from north northwest to south southeast and from west to east.
M. Shokri; M. Ghorashi; H. Nazari; R. Salamati; M. Talebian; J.-F. Ritz; H. Mohammad khani; M. Shahpasand zadeh
Abstract
The Astaneh fault with a length of more than 75 km is located in NW of Damghan. Morphotectonic investigation along the Astaneh fault and left - lateral displacement in quaternary deposits shows that, Astaneh is an active fault. It is necessary to recognize paleoseismicity of Astaneh fault because, this ...
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The Astaneh fault with a length of more than 75 km is located in NW of Damghan. Morphotectonic investigation along the Astaneh fault and left - lateral displacement in quaternary deposits shows that, Astaneh is an active fault. It is necessary to recognize paleoseismicity of Astaneh fault because, this fault is located in seismic zone of Komes historical earthquake with Ms=7.9 (Ambraseys & Melville, 1982). Many people (more than 45000) were killed in Damghan city in Komes historical earthquake. In this paper, 4-5 paleo events along the Astaneh fault are presented through paleoseismological investigation.
N. Haghipour
Abstract
Folded and faulted Kopeh Dagh-Binalud belt in the northeast of Iran is a part of Eurasia and southern margin of Touran plate. What is now observed is the result of the latest Phase of Alpine folding. The morphology of the area is in early stage and its young ...
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Folded and faulted Kopeh Dagh-Binalud belt in the northeast of Iran is a part of Eurasia and southern margin of Touran plate. What is now observed is the result of the latest Phase of Alpine folding. The morphology of the area is in early stage and its young folds express direct relevance between topography and geological structures. In order to evaluate uplift and distribution of compressional forces, stream- gradient (SL) and hypsometric (HI) analyses were carried out for 85 subbasins and 98 rivers of the major basins of the area (Atrakrud, Kashafrud, Jajarm, Gorganrud and Tourkamanestan plain rivers). Integration of the morphometric maps of SL and HI illustrates clearly the tectonic anomalies. Five highly uplifted morphotectonic zones were identified based on the morphotectonic indices as follows:
1) The middle part of Ashkabad Fault between geographical coordinates of: 56 47 E, 38 35 N to 57 34 E, 37 56N.
2) Gorganrud's sub-basins particularly located between Shavard fault (in the south) and eastern part of the Khazar fault (in the north).
3) Basins associated with Nokhandan, Qareh –Dagh, Sorkhdeh and Amrudak Faults.
4) Basins associated with Shogan and Gelli Faults are the Jajarm subbasins.
5) The northern foothill basins of BinaludMountain, compared with the southern foothill basins, show remarkable higher uplifting and shortening which seem to be related to the Binaloud and North Neyshabur fault.
In addition to high uplifted zones, some intermediate – low uplifted zones such as west - southwest part of Sarakhs, southern foothill subbasins of Atrakrud (associated with Takalkuh Fault and Ashkhaneh fault zone), Jajarm's subbasin in the eastern part of AladaghMountain were recognized.
