Original Research Paper
Volume 24, Issue 1393 , March 2015, Pages 1-1
Original Research Paper
Volume 24, Issue 1393 , March 2015, Pages 2-2
Original Research Paper
Volume 24, Issue 1393 , March 2015, Pages 3-3
Original Research Paper
N Bayeste Hasty; A Saidi; A Shahidi
Abstract
In order to investigate the structural evolution and paleo-stress analysis of the study area, North of Qazvin, geometry and kinematics of faults in are measured. Following these measurements, the stress tensor and variation of stress direction in diffeerent rock units are calculated. For this purpose, ...
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In order to investigate the structural evolution and paleo-stress analysis of the study area, North of Qazvin, geometry and kinematics of faults in are measured. Following these measurements, the stress tensor and variation of stress direction in diffeerent rock units are calculated. For this purpose, 186 fault surfaces and sliken lines from 12 sites were selected and measured. The results of the dynamic analyses using Angelier’s (1991) inversion method indicate that the stress direction changed during Eocene. They also show some change in the stress field direction occurred after Eocene time. According to our dynamic analyses on the faults, we classified the tectonic events in the study area. Principal stress axes and their directions for all sites are calculated using Angelier’s software. Results of our study indicates that the main stress dominated in this area is an extension during Eocene. Analysis of the obtained data from this part of the western AlborzMountains (north Qazvin), indicates a major NE-SW extension in the Eocene volcanic and sedimentary rocks. This extension direction is also confirm by the direction of volcanic dykes which have intruded in the same period in this area.
Original Research Paper
M Mojarab; H Memarian; M Zare; V Kossobokov
Abstract
The earthquake of 23 October 2011, near the Turkish city of Van, had 600 victims and caused great damages in Van, Argis, Moradiyeh and Caldiran. Review of 20th century and historical earthquakes in eastern Anatolian plate and west of Iranian plateau confirmed the activity of this area with the notable ...
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The earthquake of 23 October 2011, near the Turkish city of Van, had 600 victims and caused great damages in Van, Argis, Moradiyeh and Caldiran. Review of 20th century and historical earthquakes in eastern Anatolian plate and west of Iranian plateau confirmed the activity of this area with the notable earthquake of 24 November 1976 in Caldiran. The main objective of this paper is evaluation of predictability of earthquakes in this region. Presently, the two main approaches for predicting extreme events are precursory and pattern recognition algorithms. For this study, we applied M8 algorithm that is based on pattern recognition. In this respect,a 49 point network were designed around the epicenter of Van earthquake and M8 algorithm applied to this network. The end result was four zones with some overlaps that were proposed as CTIP (current time of increase probability). This study could predict the Van earthquake with 1/1/2008 to 30/12/2012 time window, 281 km local radius and magnitude of more than 7. In addition, forward prediction in this area shows there is no alarm for magnitude 7+ in next 5 years. This study showed the strength of M8 algorithm for predicting earthquakes in the Middle East. It can be concluded that using algorithms based on pattern recognition can play an important role for mitigation of damages in seismic events.
Original Research Paper
M Sarhangi; A Solgi; A Sorbi; B Fayyazi; Sh Soltani
Abstract
In this paper, the relative active tectonics of the Mordaq-Chai basin has been discussed according to the geomorphic indices using Global Mapper software. The calculated indices are as follows: stream length–gradient index (SL), hypsometric integral (Hi), ratio of valley floor width to valley height ...
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In this paper, the relative active tectonics of the Mordaq-Chai basin has been discussed according to the geomorphic indices using Global Mapper software. The calculated indices are as follows: stream length–gradient index (SL), hypsometric integral (Hi), ratio of valley floor width to valley height (Vf), index of drainage basin shape (Bs),index of mountain front sinuosity (Smf), asymmetry factor (AF), and transverse index of basin topographic symmetry (T). Using above indices results, led to calculation of relative tectonic activity index (Iat).The results show that the Mordaq-Chai basin’s relative tectonic activity index falls into two groups: the first one includes the areas around the Sahand volcano crater (upper part of sub-basin one) and the Goshayesh Valley (upper part of sub-basin three), both of which have high levels of relative tectonic activity. The second one includes high lands located at northern part of the Maragheh fault towards the Kordeh-Deh village (sub-basins one and two), the opening of the Mordaq-Chai river into the Malekan plain (from the Ekiz village to the Sheikh-o-eslam village in central of sub-basin 3) and the southern portion of the Sahand Volcano’s crest (central part of sub-basin one), which all have moderate levels of relative tectonic activity.
Original Research Paper
H Gerivani; N Hafezi Moghaddas; E Haghshenas; E Abdollahi Fard
Abstract
Notwithstanding geological and geophysical surveys and studies for hydrocarbon reservoir detection cost very much, those have lots of uncertainties. Then, engineers and scientists try to find and use new methods. Recently, some studies have suggested using ambient noise as a tool for hydrocarbon reservoir ...
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Notwithstanding geological and geophysical surveys and studies for hydrocarbon reservoir detection cost very much, those have lots of uncertainties. Then, engineers and scientists try to find and use new methods. Recently, some studies have suggested using ambient noise as a tool for hydrocarbon reservoir investigation. This new passive seismic technique, named HyMas, is based on the positive energy anomaly in data spectra between 1 to 6 Hz for microtremor measurements over reservoirs, which are called hydrocarbon microtremors. Despite the acceptable results obtained by the HyMas technique, there are many unknowns, especially concerning the source and generation mechanism of hydrocarbon microtremors and the relations between reservoir characteristics and the attributes of hydrocarbon microtremors. In this study, it has been tried to review the published experiences and studies and conclude the results and findings.
Original Research Paper
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.
Original Research Paper
R Khavari
Abstract
Stream gradients of rivers bedrock in the Khuzestan province were calculated, using GIS and 50-m digital elevation models to discuss the distribution of knick zones. Gradients were classified into local and regional types based on the measurement lengths of stream gradients for 474 rivers having at least ...
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Stream gradients of rivers bedrock in the Khuzestan province were calculated, using GIS and 50-m digital elevation models to discuss the distribution of knick zones. Gradients were classified into local and regional types based on the measurement lengths of stream gradients for 474 rivers having at least 10-km long in the study area. The transition rate from the local to regional gradients, i.e. the decreasing rate of gradient with increasing measurement length, is then obtained as the indicator of relative steepness of a river segment, which permits the objective identification of fluvial knick zones. Knick zones occur widely in the study area. The knick zones with large relative steepness near the outlets of large watersheds are related to the tectonic activity and most of them are actually close to the known locations of the active faults. The most important active faults in the study area are Mafaron, Agha-jari, Andakan, Lahbari, Mordehfel, Maron, North Behbahan Dezfol and Mishdagh. Knick zones occur along upstream steep reaches can be related to active hydraulic and erosional conditions regardless of geological or tectonic conditions. Effects of rock properties on the frequency and form of knick zones are observed, but they seem to play only a subordinate role. This study concludes that tectonics and geology are more important than topographic and hydraulic conditions in knick zone existence.
Original Research Paper
F Porghiasian; E Gholami; M.M Khatib
Abstract
In this study, value of shear strain for the Koch fault zone was determined based on the angle of foliations with the edge of the Koch fault zone. The Koch fault zone with N-S trend is located in northeast of Birjand, at the end northwest of the Sistan structural zone. In the Koch fault zone shear strain(γ) ...
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In this study, value of shear strain for the Koch fault zone was determined based on the angle of foliations with the edge of the Koch fault zone. The Koch fault zone with N-S trend is located in northeast of Birjand, at the end northwest of the Sistan structural zone. In the Koch fault zone shear strain(γ) was calculated based on the foliations, which are from the types of fracture cleavage. Shear strain in central part of the Koch fault zone reaches to 4 degrees, its maximum. The value of shear strain reaches to 2 degrees in southern and northern parts of the Koch fault. The value of shear strain decreases from central part of the Koch fault towards the northern and southern parts. The latter indicates the growth of the fault from the central to the northern and southern parts.
Original Research Paper
B Esmaeili; M Almasian; B Samani; A Samani
Abstract
Ahwaz city, the center of the Khuzestan province, is located in southwest of Iran. The four main geological phenomena of this area are Ahwaz Fault, Ahwaz Anticline, Aghajari Formation, and Quaternary Alluvium and Eluvium Deposits. The Ahwaz Urban Railway Project and its related comprehensive geological ...
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Ahwaz city, the center of the Khuzestan province, is located in southwest of Iran. The four main geological phenomena of this area are Ahwaz Fault, Ahwaz Anticline, Aghajari Formation, and Quaternary Alluvium and Eluvium Deposits. The Ahwaz Urban Railway Project and its related comprehensive geological and geotechnical studies were started in 2006 and the first phase of the project consisted of 24 Km parallel twins tunnel & 24 stations. The project level is -17.5m beneath the ground surface, except for the crossing with the KarounRiver. The twin tunnels cross under the KarounRiver in lower elevation. The most important part of the project is crossing safely under the KarounRiver. Therefore, this area, which is located in the southern vicinity of the Ahwaz Fault, was studied precisely by surface and under-ground methods. The Ahwaz Fault divides AhwazCity into two sections. The north, north-east section (hanging wall), which depth of the bed rock is 8-12m and is covered by young quaternary sediments, and south, south-west section (foot wall), which its bed rock is settled down totally and cannot be reached by geotechnical drilling. The Karoun River has meander form in the Khouzestan Province (also north and south of Ahwaz City), but in center of the city (especially in crossing with the Ahwaz Fault) this form changes into straight shape, so it means that the Karoun River channel in center of Ahwaz is young and affected by the Ahwaz Fault. The logs of geotechnical drilling in river bed and river banks were studied vertically and horizontally in order to find out the stratigraphic changes of the KarounRiver sediments. These studies show that stratigraphic sections of the Karoun River reveres from west to east horizontally and also vertically in recent thousands years in crossing area with the Ahwaz Fault. These evidences support the hypothesis of affection of the Ahwaz Fault activity on the KarounRiver movement. Therefore, the age of river bed deposits was measured by thermal luminescence method in order to realize the age of one the main Ahwaz Fault activities, which change the river channel. The results of age dating show that the old river channel has changed to the recent one about 4000 years ago. In other words, the KarounRiver channel changed after an earthquake struck this area. In addition, two new faults were discovered in the Foroodgah square and the Mosala stations during the excavation in north-northeast of the Ahwaz Fault. An inferred fault was discovered in the CulturalCenter station as well.
Original Research Paper
M Ramazani; M.R Ghassemi
Abstract
The erosional window of Aghdarband, located in NE Iran and SE of Mashhad is a unique place to study of the Eo-Cimmerian event. This event (Late Triassic-Middle Jurassic) resulted from closure of the PaleotethysOcean and collision between the Iran and Turan plates. In this study, we have tried to analyze ...
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The erosional window of Aghdarband, located in NE Iran and SE of Mashhad is a unique place to study of the Eo-Cimmerian event. This event (Late Triassic-Middle Jurassic) resulted from closure of the PaleotethysOcean and collision between the Iran and Turan plates. In this study, we have tried to analyze the microstructural features of the exposed carbonate units (the Sefid Kuh formation of the Early Triassic age and some Paleozoic units) in the Aghdarband area. The average of ellipticity calculated for the calcite grains is about 0.78 located in the oblate part of the Flinn diagram. The estimated kinematic vorticity number is 0.6 - 0.7. The calcite twining in the carbonate units exposed in the Aghdarband area indicate temperatures of about 180-200˚C and differential stresses of about 180-240 MPa during the main deformational event of the area (Eo-Cimmerian).
Original Research Paper
M Ehteshami-Moinabadi; A Yassaghi
Abstract
The assessment of deformation condition of the Mosha Fault during Middle-Late Miocene carried out using microstructure and thermometry of fluid inclusions within calcite veins in the fault zone. Based on intra-crystalline deformation of quartz grains, calcite twin, and thermometry of primary fluid inclusions ...
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The assessment of deformation condition of the Mosha Fault during Middle-Late Miocene carried out using microstructure and thermometry of fluid inclusions within calcite veins in the fault zone. Based on intra-crystalline deformation of quartz grains, calcite twin, and thermometry of primary fluid inclusions in the calcite veins inside the Mosha fault zone, the maximum estimated deformation temperature of the Mosha fault is 350o c during Tertiary. Calculated pressure of the fault zone using fluid inclusion data is an underestimation of real pressure because the calcite veins formed in the last stages of deformation. Considering the tectonic setting of South Central Alborz and assuming a geothermal gradient ranging between 25-35oc/Km for the region from Eocene to the late Miocene, the maximum temperature of 350o c represents the depth between 10 to 14 Km in adiabatic condition. This depth range means a fault zone pressure between 2.5 to 4 kbar for the Mosha Fault zone during Tertiary, which is in correlation to recent seismic data that confirmed maximum fault activity in the depth between 10 to 15 Km.
Original Research Paper
H Nikoogoftar; A Bahroodi; B Tokhmchi; G.H Norouzi; B Mehrgini
Abstract
Identifying and interpreting subsurface heterogeneities, especially Litofacies, plays definitely an important role in assessing and managing hydrocarbon resources. Variety of methods have been developed in order to model discrete features of hydrocarbon reservoirs, as Litofacies, which the majority of ...
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Identifying and interpreting subsurface heterogeneities, especially Litofacies, plays definitely an important role in assessing and managing hydrocarbon resources. Variety of methods have been developed in order to model discrete features of hydrocarbon reservoirs, as Litofacies, which the majority of them have focused on intra-well modeling, and are not applicable for 2D or 3D modeling between oil wells. Furthermore, developing a novel methodology to bring a more factual reservoir facies has always been a matter of attraction, and is effective in lowering risk of decision making in different exploratory stages. These days, Markov Chains is used as a powerful tool for facies modeling. This method is based on conditional probabilistic and providing transitional matrix of states. This study is carried out on an oil field, South-West Iran; where the Asmari Formation is its main reservoir. Here, interval of the Asmari Formation and its cap rock in a 12 kilometers long section, 110 meters width, is classified into three main parts, by the means of Markov Chains modeling. The best result of modeling was obtained with nine wells and four seismic horizons that brought 87% accuracy in average.
Original Research Paper
R. Arfania
Abstract
The study area, located in the east of Eghlid town, between the northeast of the Abadeh Fault and southwest of the Zagros Main Fault, consists of the highly deformed rocks, which have been emerging clearly in tectonic crashed zone. Kinematic analysis carried out for determining the paleostress directions ...
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The study area, located in the east of Eghlid town, between the northeast of the Abadeh Fault and southwest of the Zagros Main Fault, consists of the highly deformed rocks, which have been emerging clearly in tectonic crashed zone. Kinematic analysis carried out for determining the paleostress directions and deformation history of the area. Thus, the geometry of the fault plan/fault zone brittle structures and other kinematic indicators were measured based on the field observations and analysis carried out via data analysis inversion method and statistical models. The geological evidences provided necessary data for determining formation ages of the structures based on the relative time scale. According to the results, it can be concluded that three different faulting phases were efficacious in formation of the analyzed faults. During the faulting phases, three reverse fault systems developed respectively; imbricate fans thrust system, hinterland dipping duplex and inverted normal faults.
Original Research Paper
SH Pourbeyranvand; M Tatar
Abstract
Having knowledge of stress variations in the Zagros region, southwest Iran is necessary to study the deformation resulting from oblique collision between the Eurasian & the Arabian plates and to obtain insight into the complicated tectonics of the region. In this study, earthquakes focal mechanism ...
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Having knowledge of stress variations in the Zagros region, southwest Iran is necessary to study the deformation resulting from oblique collision between the Eurasian & the Arabian plates and to obtain insight into the complicated tectonics of the region. In this study, earthquakes focal mechanism data were used to collect information on the state of stress in 12 subdivisions of the data including teleseismic and local events in the Zagros region. The stress axis show noticeable variations in the Zagros region, especially around the Oman Line. The angular difference between the stress & strain axis increases from the southeast to the northwest of the ZagrosMountain. The deformation partitioning due to pre-existing faults and fractures and introducing a weak zone in the NW Zagros under the influence of the Main Recent Fault activity may explain this increasing.
Original Research Paper
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.
Original Research Paper
M.S Mirabedini; M Agh-Atabai
Abstract
In this research, to investigate seismic pattern and precursory properties of fractal dimensions, spatial distribution and temporal variations of correlation dimensions of epicentral, De, and temporal distribution of earthquakes, Dt, before the Baladeh-Kojour earthquake have been studied. The May 28th, ...
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In this research, to investigate seismic pattern and precursory properties of fractal dimensions, spatial distribution and temporal variations of correlation dimensions of epicentral, De, and temporal distribution of earthquakes, Dt, before the Baladeh-Kojour earthquake have been studied. The May 28th, 2004, Baladeh-Kojour earthquake with Mb= 6.2 (ISC), which is one of the largest earthquake in the vicinity of Tehran, was occurred in the northern part of the Alborz mountain ranges. The spatial distribution maps show decreasing in De and Dt in the eastern part of the epicenter, which is observed at 2002 in the temporal variation plots. With respect to space-time plot, it seems that this decreasing caused by the earthquake clusters that were occurred between 2002 -2003. Investigation of seismic pattern based on spatial and temporal variations of fractal dimensions and space-time plot of earthquakes demonstrate doughnut pattern (some earthquake clusters and a lot of small events) and seismic quiescence before the main shock. The results indicate that fractal dimensions are sensitive to clustering in space and time. So, the spatial and temporal variations of these parameters can be used as a precursory phenomenon, which is caused by seismic activation and quiescence.
Original Research Paper
M Nemati; J Hollingsworth; M.R Ghassemi
Abstract
Our research focuses on the seismotectonics of the north of Eastern Alborz and southeast of the Caspian Sea. Eastern part of the Caspian fault, and seismological active plain situated in north of the area have been studied. The seismological data of microearthquakes (ML>4.5) recorded by the local ...
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Our research focuses on the seismotectonics of the north of Eastern Alborz and southeast of the Caspian Sea. Eastern part of the Caspian fault, and seismological active plain situated in north of the area have been studied. The seismological data of microearthquakes (ML>4.5) recorded by the local network of the Geological Survey of Iran (installed during 2009 and 2010) and regional seismicity located by seismological networks of the Geophysics Institute of University of Tehran and International Institute of Earthquake Engineering and Seismology of Iran were used. Also geomorphological evidences in the area and dynamic parameters of the 1985 Gorgan earthquake, MS=6.0, are included for getting a better justification. Although deep thrust mechanisms of the 1999, 2004 and 2005 earthquakes indicate N-S compressional regime at depth and normal component of shallow earthquakes (ML>4.5) shows extensional regime at near surface in southeast of the Caspian Sea. The morphological evidences confirm this normal kinematics. In addition, the dynamical parameters of the 1985 Gorgan earthquake and its focal mechanism introduce the Caspian fault as the source of this thrust earthquake. All evidences confirm probable underthrusting of southeast of the CaspianBasin beneath the Eastern Alborz.
Original Research Paper
M.E Hekmatian; V Ebrahimzadeh Ardestani; M.A Riahi; A Memar Koucheh Bagh; J Amini
Abstract
Pattern recognition algorithms especially neural network in geophysical interpretations and other Earth sciences have been used since some years ago. In neural network and other pattern recognition algorithms like support vector classifier (SVC) that the latter method is used in this research, by using ...
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Pattern recognition algorithms especially neural network in geophysical interpretations and other Earth sciences have been used since some years ago. In neural network and other pattern recognition algorithms like support vector classifier (SVC) that the latter method is used in this research, by using the values of the features, which has been extracted from the objects (in our work gravity profiles are objects), classification of the objects can be done. Usually the features are selected subjectively. In this paper, we have presented a homemade software that can select proper features objectively. By using SVC and the mentioned features selection (FS) software, depth estimations of anticlines have been done in this research. We have shown the difference of using proper features and improper ones in the mentioned depth estimation (a kind of classification). In this paper, twenty synthetic gravity profiles with anticline shape sources are created for training SVC and the same amount of synthetic profiles are created for testing. It has shown that depth estimation with proper features is more precise than depth estimation with improper features. Also it should be emphasized that FS is important not only in depth estimation of anticlines, but also in all kinds of classifications in Earth sciences and the mentioned homemade software code is applicable in all of them.
Original Research Paper
H Hajialibeigi; S.A Alavi; J Eftekharnezhad; M Mokhtari; M.H Adabi
Abstract
The Kaseh Mast anticline located in the south of the Lurestan zone, is one of the small-scale anticlines in the Lurestan (in north) and the Dezful Embayment (in south) zones in the Zagros fold-thrust belt. This anticline and the adjacent anticlines are affected by the Balarud blind thrust fault zone, ...
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The Kaseh Mast anticline located in the south of the Lurestan zone, is one of the small-scale anticlines in the Lurestan (in north) and the Dezful Embayment (in south) zones in the Zagros fold-thrust belt. This anticline and the adjacent anticlines are affected by the Balarud blind thrust fault zone, which is a part of the Mountain Front Fault. The Mountain Front Fault is a major topographic front that be traced along the Zagros fold-thrust belt in the Izeh, Fars, Lurestan and Dezful Embayment. The field observations and geometric analysis indicated that the axial trend of the Kaseh Mast anticline has been changed and shows asymmetrical, noncylindrical and disharmonic fold, with vergence to southwest. The class of folding is 1C subclass of Ramsay's classification. To determine the geometry of the fold the termsof open for tightness, wide for aspect ratio and subrounded for relative curvature are suggested. In addition, this anticline is analyzed by using of geometrical models. Basically, this model allows quantitatively predicting the Balarud blind thrust fault zone trajectory and displacement from the geometric characteristics of this anticline. The comparison of the anticline with the theoretical fault-related folding models suggests the Kaseh Mast anticline as an Asymmetrical Detachment Fold that is affected by the Balarud fault zone. It is probable that the folding process of the Kaseh Mast anticline is in early states of the formation of a detachment fold. However, the folding mechanism of the adjacent anticlines is fault-propagation folding. The changing of the folding mechanisms of this anticline and the adjacent anticlines from detachment (in Kaseh Mast anticline) to fault-propagation folding (in the Siah Kuh and Chenareh anticlines) is probably referred to several parameters. These include the effect of thrust, the position of the Kaseh Mast anticline in Zagros fold-thrust belt, the distance of the anticlines related to the Balarud fault zone and the potentiality of the changing of the folding mechanisms of triple fault-related folding to each other.
Original Research Paper
Y Jalili; M.M Khatib; E Gholami; M.R Ghassemi
Abstract
The Chelounak area in northwest of Birjand located in the Sistan suture zone extremity with middle-upper Eocene sedimentary and pyroclastic rocks, folded with different axes and exposed between the Chahak-mosavieh and Mohammadieh-Hessarsangi faults. These folds have a dominant characteristic of the dispersion ...
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The Chelounak area in northwest of Birjand located in the Sistan suture zone extremity with middle-upper Eocene sedimentary and pyroclastic rocks, folded with different axes and exposed between the Chahak-mosavieh and Mohammadieh-Hessarsangi faults. These folds have a dominant characteristic of the dispersion axis trends of NE-SW, NW-SE, and N-S. Geometric-Kinematic Analysis of these folds was carried out by data that taken from the structural interpretations, satellite images, geological maps, structural cross sections and mathematical functions. Aspect ratio, percent shortenings and the rotation folds axes are respectively for folds with NE-SW axis, 0.356-1.6, 20-77% and 28-40°; for folds with NW-SE axes0.352-0.620, 25-41% and 25-40°; and for folds with N-S axes 0.352, 25% and 24°. In this analysis the Chahak and Chelounak synclines and the Chahak anticline with NE-SW axis have maximum shortening and the Shavangan syncline with NW-SE axis has minimum shortening. This Study demonstrated the aspect ratio rises with increasing of shortening. Analysis of the structural elements demonstrates axis change of the Chelounak, Chahak and Hoj noj synclines and the Chahak and Chelounak anticlines with NE-SW Dominant axes affected by the Chahak-Mosavieh fault (~N-S trend) as well as the axis change of the Taj kouh, Shavangan and Hessar sangi synclines with NW-SE dominant axes affected by the Mohammadieh-Hessar sangi fault (~N-S trend). Dispersion of folds axial respect to compressive component has caused difference in aspect ratio, shortening and rotation of fold axes values.
Original Research Paper
D Iranbodi; M Zare
Abstract
The south of Tehran lies in vicinity of the active faults such as Pishva, Kahrizak and Eyvan-E Key and in the case of re-rupturing of these faults a serious disaster, perhaps financial and life losses may be occurred. In IBC (International Building Code) formula (Darlene & Batatian, 2002) dip, displacement ...
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The south of Tehran lies in vicinity of the active faults such as Pishva, Kahrizak and Eyvan-E Key and in the case of re-rupturing of these faults a serious disaster, perhaps financial and life losses may be occurred. In IBC (International Building Code) formula (Darlene & Batatian, 2002) dip, displacement and footing of building and criticality of building code have been considered as important factors for setback zone. In up thrown side we must: S=U (2D+F.tan-1θ) . In down thrown side we must: S=U(2D) . There is gap of world standard setback zone in Pishva. The Iranian setback zone code does not respect the IBC formula and is based on the field observations. the formula of IBC consider slip rate of the fault, the displacement factor, the type of structure, foundation of the building and the sensitivity of structure, while in Iran the zoning of the Berberian et al. (1364), which is based on the fault type and field observations has been continuously used. Thus, with combination of these two methods and with regard to the geotechnical issues, construction can be designed more carefully.
Original Research Paper
H Haji Hosseinlou; A Solgi; M Mohajjel; M Pourkermani
Abstract
The Khoy shear zone (KSZ) is exposed 130 Km north of Uremia and 650 km west of Tehran. Structural analysis in the Khoy Shear Zone (KSZ) indicated that they consist of NW-SE oriented various metamorphic rocks. They contain NW-SE trending moderate to steeply dipping mylonitic foliation to the NE. Stretching ...
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The Khoy shear zone (KSZ) is exposed 130 Km north of Uremia and 650 km west of Tehran. Structural analysis in the Khoy Shear Zone (KSZ) indicated that they consist of NW-SE oriented various metamorphic rocks. They contain NW-SE trending moderate to steeply dipping mylonitic foliation to the NE. Stretching lineation plunge shallowly to moderately towards NE. Thrust faults are oriented the same as mylonitic foliation. Ductile fabrics are superimposed by brittle structures. Orientation of the structures indicates that the main stress trend is NE-SW. Four deformation stages (D1-D4) identified in KSZ. The first two stages are ductile that superimposed by the two other ductile-brittle stages. Shear sense indicators such as S/C fabrics, shear bands, shear folds, book-shelf structures, fishes and mantled porphyroclasts indicate that the KSZ deformed via dextral transpression tectonic regime. The Khoy area contains both NW-SE striking dextral strike-slip and SW verging NE dipping ductile reverse shear fabrics. Ductile shear fabrics are overprinted by subsequent younger both thrust and strike-slip fault systems. Abundant syn-tectonic granitoids were intruded in the Khoy area during convergent. The shear deformation fabrics are well identified in both deformed intrusive and metamorphic-ophiolite complex. The geometry and kinematics of shear fabrics indicate a deformation partitioning in both ductile and brittle conditions during a progressive transpression tectonic regime. The KSZ deformed during an oblique convergence scenario between the Arabian and West Alborz- Azerbayjan blocks in NW Iran.
B Derikvand; A Yassaghi
Abstract
The folding style analysis is one of the initial investigations on hydrocarbon reservoirs anticlines. Nader Anticline is located in the western part of the Eastern Kopeh Dagh zone and on hanging wall of the North Kopeh Dagh Reverse Fault. The structural analysis of the anticline is carried out along ...
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The folding style analysis is one of the initial investigations on hydrocarbon reservoirs anticlines. Nader Anticline is located in the western part of the Eastern Kopeh Dagh zone and on hanging wall of the North Kopeh Dagh Reverse Fault. The structural analysis of the anticline is carried out along eight structural transects across the fold. This analysis showed that the Nader Anticline has two culminations with an en echelon arrangement. These culminations as well as the other folds in the study area are cross cut by a series of NW- and N- trending strike-slip faults. The Nader Anticline first culmination is analyzed as fault propagation fold geometry, while its second culmination is examined as fault detachment fold geometry. Since the Nader Hidden Fault cuts the north limb of the first culmination; the geometry of this culmination can also be considered as faulted detachment fold. The study area faults though have different trends but they dominantly have strike-slip mechanism or strike-slip component and thus, can be considered as Riddle shear faults. Geometric and kinematic analysis of these faults showed that a series of these faults could be considered as shear fractures related to a NW-trending PDZ, while the other faults can be examined as Riddle shears related to a N-trending PDZ. Such development of the Riddle shears faults as well as en echelon arrangement of the Nader Anticline culminations imply that the study area is structurally evolved during a NW-trending oblique-slip fault system more likely related to transpressional activity of the North Kopeh Dagh Reverse fault zone.
Original Research Paper
S Shokrzade; B Voosoghi; M Amighpey
Abstract
In this paper, the Bam post-seismic annual deformations in period from 2004 to 2010 have been obtained using synthetic aperture radar interferometry. The time series of deformations have been constructed using Persistent Scatterer Radar Interferometry technique. When displacements rate in the area are ...
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In this paper, the Bam post-seismic annual deformations in period from 2004 to 2010 have been obtained using synthetic aperture radar interferometry. The time series of deformations have been constructed using Persistent Scatterer Radar Interferometry technique. When displacements rate in the area are low and the pixels are with temporal decorrelation, this technique is more effective. The technique also largely reduces the topography residuals and atmospheric delay. Because of the low rates of post-seismic displacements, this technique is very useful for measuring such earth surface displacements. The results illustrate that the maximum amount of uplift and subsidence displacements for Line Of Sight (LOS) direction during 2004 to 2010 after the earthquake are 4.5± 0.5 and -4.3± 0.5 centimeter, respectively. Comparison of displacement fields demonstrates that the displacements reduction rates are approaching to the co-seismic phase. In addition, the results of post-seismic modeling proves that displacements field, follows exponential or logarithmic function.
Original Research Paper
B Zamani; M Jalilpour; M Moayyed; M Faridi
Abstract
The Study area is located in 15km Northeast of Tabriz in East-Azarbaidjan province. The rock units in the study area are limited and consist of different members of the Upper red formation (Miocene). Salt bed (Miocene) that diapired is related to the base of the mentioned formation. Due to the rising ...
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The Study area is located in 15km Northeast of Tabriz in East-Azarbaidjan province. The rock units in the study area are limited and consist of different members of the Upper red formation (Miocene). Salt bed (Miocene) that diapired is related to the base of the mentioned formation. Due to the rising of this salt diapir, various structures such as marginal reverse faults, radial normal faults, folds and karsts are developed. In the Northern part of the Tabriz fault, there are a set of basin structures and diapirs, which all have a NW-SE extension axis. The Khaje salt diapir is formed in the southern margin of one of these basins. The different parameters affecting the rising of this salt diapir from which the most important one is the tectonic regime of the study area. The compressional stress causes the formation of these basins. Furthermore, the contact between the Tabriz fault and Nahand (NW-SE) minor fault prepared a weak zone to rise the Khaje salt diapir. After the beginning of rising, other parameters such as buoyancy force, stability of compressional stresses and differential loading have caused the continuing and rising of the Khaje salt diapir. The Khaje salt diapir is young and still rising. In addition, analytical model analysis is evaluated diapirism initiation time about 31000 years. In terms of purity amount, NaCl percentage is very high; where there are no KCl and MgCl2 impurities; therefore, it is suitable for dissolution process. The marly interbeds of salt would make some difficulties in dissolution process. From the gas storage point of view, the depth of salt diapir and the evaluation of the reservoir volume are essential for underground researches and in order to get the accurate results 2D and 3D seismic studies are needed.
Original Research Paper
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.
Original Research Paper
A Salehpour; B Oveisi; M.R Ghassemi
Abstract
In thin-skinned fold-thrust belts, the style of deformation is critically depends not only on the resistance to sliding along basal detachment, but also on the presence of intermediate decollement levels or/and ductile units within the wedge. In ZFTB the incompetent units known as detachment levels like ...
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In thin-skinned fold-thrust belts, the style of deformation is critically depends not only on the resistance to sliding along basal detachment, but also on the presence of intermediate decollement levels or/and ductile units within the wedge. In ZFTB the incompetent units known as detachment levels like the Gachsaran formation (Shallow level) and the Hormuz salt series (deep) affect strongly the deformation style. However, in many cases shallow level detachment of the Gachsaran unit controls this shallow deformations, but owing to the different facies of this unit in the studied area it is reasonable to other incompetent shallow units (e.g. the middle Miocene Mishan Fm. and the Upper part of Aghajari Fm.) to partially decoupling deformation form the underlying sedimentary units, and have permitted the re-activation of pre-existing syncline structures, through upward extrusion of the syncline core. Owing to the concentration of significant amounts of young deformation across the structure (specially northern hinge) in the style of erosional surfaces, the East-West trending Anve syncline in north of the Bastak town, considered to be one of the most active structures in the region. In this study, we try to define the vertical deformation of a geomorphic marker as well as using tectonic morphology techniques to shed light on the deformation extend and pattern in the eastern and western parts of the structure . However, the microseismic data do not suggest any significant event related to this kind of deformation, but studying deformation style and relative uplift rate estimation could be beneficial dealing with earthquake hazards in the region.
Original Research Paper
M Agh-Atabai
Abstract
In this paper, the properties of temporal distribution of earthquakes in southeast Zagros were studied using multifractal methods. To describe the multifractal characteristics of the occurrence time of events, the generalized correlation dimensions Dq and the singularity spectrum f(αq) were calculated ...
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In this paper, the properties of temporal distribution of earthquakes in southeast Zagros were studied using multifractal methods. To describe the multifractal characteristics of the occurrence time of events, the generalized correlation dimensions Dq and the singularity spectrum f(αq) were calculated for earthquake sequence with magnitudes equal to or larger than the completeness magnitude (M= 4.5). In order to investigation of the spatial variations of seismicity pattern, the study area is divided into the three subareas and the results of the analyses were compared to each other. The calculated multifractal spectra for all subareas indicate that the pattern of seismic activity in these regions is a heterogeneous multifractal phenomenon. However, the graphs of correlation integral functions of the studied subareas have clear differences. Except the transition zone on which there are three scaling ranges, the other subareas show two scaling ranges: short and long time scales. The properties of short time scale are controlled by the distributions of small earthquakes (e.g. aftershocks) in clusters, whereas the long time scale is related to the distribution of larger main earthquakes and the clusters related to them. In the graph of transition zone, the large time scale is divided into two different ranges with a characteristic break on about 3.6 years. This characteristic length means there is another kind of clusters (main shocks) rather than the small earthquake clusters. The graphs of recurrence time of earthquakes support these results and show the shorter recurrence time of events in the transition zone. In addition, the results show that the transition zone has a more heterogeneous multifractal pattern rather than its surroundings.
Original Research Paper
N Saboor; M.R Ghassemi; M Eskandari; A Nazari F; B Oveisi
Abstract
Erosion agents diffuse the scarps created by the earthquakes, are and their primary sharp shapes are gentled. This process is accomplished with the definite rate, which is accounted with the diffusion equation. Rate of diffusion depends on primary shape of scarp and diffusion coefficient that is coefficient ...
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Erosion agents diffuse the scarps created by the earthquakes, are and their primary sharp shapes are gentled. This process is accomplished with the definite rate, which is accounted with the diffusion equation. Rate of diffusion depends on primary shape of scarp and diffusion coefficient that is coefficient of diffusion equation. The coefficient depends on various parameters such as the climate and the value of erosion of scarp material. The coefficient is accounted with the modeling of earthquake scarp with the definite age and initial shape. We afforded three profiles from the Salmas earthquake scarp created in 1930. We diffused the reconstructive primary shape of them by the code that we wrote in the Matlab software. We present diffusion coefficient of the Salmas area, and the mean of definitive coefficient. This coefficient is used for other earthquake scarps and traces in this and other areas with the same climate. The age of their formation was calculated by this coefficient and the prepared profiles.
Original Research Paper
H Nazari
Abstract
Many attempts have been done to prepare active faults map of the greater Tehran region, in order to evaluate of probabilistic seismic hazard of the region. Insufficient data about the depth and nature of seismic layer, lack of enough numerical information about the crustal deformation rate, and little ...
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Many attempts have been done to prepare active faults map of the greater Tehran region, in order to evaluate of probabilistic seismic hazard of the region. Insufficient data about the depth and nature of seismic layer, lack of enough numerical information about the crustal deformation rate, and little knowledge about the background seismicity and characteristics of seismic sources, such as seismogenic faults, magnitudes and occurrence interval act as barriers to achieve this evaluation perfectly. In this paper, based on the numerous researches done in seismology, geodynamic and paleoseismology during the last decade, attempt has been done to provide statistical analysis on the basis of paleoseismological studies on major faults of the region such as Astaneh, Firouzkuh, Mosha, Taleghan, North Tehran, Pishva and North Rey as well as the Kahrizak scarps. It is worth to mention that reactivation of any of the mentioned faults could be assigned to the Tehran earthquake, certainly with completely different size affects. According to basis of the extensive paleoseismological data together with morphotectonic investigations in the Central Alborz, the occurrence of a 6.5-7.2 magnitude earthquake during the next 50 years, in the vicinity of Tehran might be probable.
Original Research Paper
A Rashidi; M.M Khatib; M.R Heyhat; S.M Moussavi
Abstract
In KamarhajiMountain, NW Birjand there are geological structures such as: duplex, pop-Up, triangle zone, flower structures, folding, etc. The duplexes in KamarhajiMountain have E-W trend. They are parallel to the Shekarab fault system. The Shekarab fault is a reverse fault with sinistral component located ...
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In KamarhajiMountain, NW Birjand there are geological structures such as: duplex, pop-Up, triangle zone, flower structures, folding, etc. The duplexes in KamarhajiMountain have E-W trend. They are parallel to the Shekarab fault system. The Shekarab fault is a reverse fault with sinistral component located in the southern of the area; it is considered as one of the terminal branches of the Nehbandan fault. Based on the Geometric-Kinematic analysis, duplexes are of the horsetail structure type, which are set from the side view on each other. There are flower structures in the direction perpendicular to the horsetail structures, caused that the central layers of the duplex structures have the maximum height. Usually in the orogenic regions, the antithetic thrusts with motion opposite to the main thrust are observed. These thrusts are called back thrusts. The hanging wall blocks of two faults, thrust and its back thrust is called pop-Up structure. In addition, in some regions back thrust and new thrust created triangle zone. In duplexes of this Region, ramps have strike slip mechanism with Thrust component. The existing flats are non-horizontal and most of them have thrust mechanism with strike slip component. Due to the mechanism of flat, transfer direction is westward, and since the younger ramps are formed on the hanging wall of previous ramp (In other words, younger orientation is toward the hinterland) the formation of duplexes follows the break-back model. Since the physical model shows a better understanding of the formation model and the relationship between the structures, we have used of the experimental model. The results of experiments show a strong relationship between the geometry of the flat and the geometry of the structures of the area. Based on the paleostress studies and different trends of shortening of structures such as folding, duplexes, two deformational stages were identified. In the first stage, position of strain λ3 axis according to analysis of the conjugate joints, tension joints, and axial surface of folding is N42, 00, N40, 07, and is N38, 14 respectively. The amount of shortening in this stage of deformation is 41.46 %. Position of strain λ3 axis in the second stage of deformation according to analysis of the conjugate joints, tension joints, and E-W trend of thrusts is N83, 02, N84, 00, and N90E respectively. In this stage, strike– slip faults have been further developed. The shortening in this stage of deformation is 20.30 % and the amount of slip along the flats is 2640 meters. According to the geometric-kinematic analysis duplexes formed in the second stage of deformation, which was progressive.
Original Research Paper
M Tatar; S.M Momeni; F Yaminifard
Abstract
The V shape kink of the AlborzMountains at its southern end reaches to the Garmsar city located 100 km southeast of Tehran metropolis. We investigated seismicity and seismotectonic features of the Garmsar area by precisely locating of microearthquakes recorded by our local dense seismological network ...
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The V shape kink of the AlborzMountains at its southern end reaches to the Garmsar city located 100 km southeast of Tehran metropolis. We investigated seismicity and seismotectonic features of the Garmsar area by precisely locating of microearthquakes recorded by our local dense seismological network and by the Iranian Seismological Center (IRSC). Our results indicate high seismic activity at the central and western parts of the Garmsar fault. Three computed focal mechanisms revealed compressional movements of the central part of this fault. Very little seismic activity is observed on the Eyvanekey and the Pishva faults. The only computed focal mechanism for the northern hills of the Garmsar fault shows tensional movements in this area, which refers to strain release among the Garmsar and Sorkheh reverse faults. Most of the calculated focal mechanisms in the Garmsar area indicate compressional and strike slip motions with overall P axis direction of 10° to 35°. The calculated P axis with NW-SE trend, close to the Sorkheh fault, is different from the other calculated P axes that show NNE-SSW direction. This is probably due to rotating of structures in this area, as revealed by recent GPS measurements in this region.
Original Research Paper
A Ahmadi-Torkmani; M.R Ghassemi
Abstract
The present research uses precise field data to provide a balanced cross-section of the Mahneshan area, and investigate nature of depth distribution of its major structures. Our structural studies indicate that the Mahneshan and Anguran faults are two major faults, which penetrate deep into the crust ...
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The present research uses precise field data to provide a balanced cross-section of the Mahneshan area, and investigate nature of depth distribution of its major structures. Our structural studies indicate that the Mahneshan and Anguran faults are two major faults, which penetrate deep into the crust and cause a considerable amount of horizontal shortening in the area. In a more specific way, the Anguran fault roots deep into the middle crustal levels of about 21 km, and thrusts the whole Phanerozoic sequence and even parts of the Precambrian basement rocks over the younger strata. We believe that the abovementioned thrust originates not from a low-competency decollement plane, but from a ductile shear zone in deep crust. Evidences for development and conditions of such shear zone are present in the Precambrian basement rocks of the Anguran fault’s hanging-wall. We suggest that the decollement surface for the Mahneshan thrust, which is located in the shallower depths (13 km), is related to probable occurrence of evaporitic materials equivalent to the Hormoz Series beneath the Kahar Formation. Syn-sedimentary deformation within the Qom Formation in the hanging-wall of the Anguran thrust, as well as other evidences present in Neogene deposits of the area suggest that the thrust fault has been active since Oligocene. Restoration of displacements across the Anguran fault, and comparing the results with inception age for the fault suggests that the Anguran fault has been active with a slip rate of about 1 mm/yr. The structural features in the Mahneshan area indicate that thick-skinned faulting along with thin-skinned tectonics have resulted in a considerable amount of thickening of the crust in the region; this observation is in accordance with abovementioned characteristic of the crust in the Sanandaj-Sirjan zone.
Original Research Paper
M.R Sheikholeslami
Abstract
The effects of the Mid-Cimmerian event in the BinaludMountains can be investigated in the Mashhad Phyllite around Mashhad and in the Aghdarband Group in the Aghdarband area. In the Eastern Binalud, this event acted in prehnite-pumpellyite to lower greenschist facies and influenced the Shemshak group, ...
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The effects of the Mid-Cimmerian event in the BinaludMountains can be investigated in the Mashhad Phyllite around Mashhad and in the Aghdarband Group in the Aghdarband area. In the Eastern Binalud, this event acted in prehnite-pumpellyite to lower greenschist facies and influenced the Shemshak group, which deposited as a post Early Cimmerian molasse blanket in a Rhaetian–Lias back-arc basin. The result is transformation of these sediments into the slate, phyllite and metasandstone. Tight to open folds, axial plane foliations and crenulation folds with NW-SE trending are the Mid-Cimmerian deformational structures. Due to the lower grade of metamorphism and deformation, there isn’t any important effect of this event on the rocks, which were previously deformed and metamorphosed by the Early Cimmerian event. The exhumation and erosion of deformed rocks by the Early and Mid-Cimmerian events generated the intramontane basins in the internal part of the eastern BinaludMountains. In the Aghdarband area, this event is characterized by folding of the Sina Formation from the Aghdarband Group, which is unconformably overlain by the Kashafroud Formation.
Original Research Paper
K Orang; M Mohajjel; G.R Tajbakhsh
Abstract
The kinematic analysis of the Koushk-e-Nosrat Fault (striking WNW-ESE) at north Saveh city indicates that since a time after early Miocene it has been inverted from dextral strike-slip (and reverse-dextral-oblique slip) to reverse-sinistral (and sinistral strike-slip( displacement. The Kinematic evidences ...
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The kinematic analysis of the Koushk-e-Nosrat Fault (striking WNW-ESE) at north Saveh city indicates that since a time after early Miocene it has been inverted from dextral strike-slip (and reverse-dextral-oblique slip) to reverse-sinistral (and sinistral strike-slip( displacement. The Kinematic evidences of right-lateral strike-slip displacement are: 1) Generation of the Koushk-e-Nosrat pull-apart basin along the bended segment of the fault in north Saveh city where a thin sequence of the Qom Formation (late- Oligocene to early Miocene) has been deposited in this narrow basin. 2) Shear bands and other kinematic indicators of right-lateral strike-slip and reverse-dextral-oblique slip displacements exist in the fault zone. 3) Synthetic right-lateral and antithetic left-lateral strike-slip faults are observed in wall damage zones around the main fault zone. The evidences of left-lateral strike-slip displacements after slip sense inversion are: sinistral- reverse faults, pure reverse faults, sinistral strike-slip faults and folds are generated in the Koushk-e-Nosrat Fault zone. The younger left-lateral reverse kinematic of the Koushk-e-Nosrat Fault is another significant evidence for the main role of the left-lateral reverse faults in deformation of the Qom-Saveh district in NW part of the Central Iran Block that has been tested before by structural and morphological kinematics of other major faults in the area like the Ipak (south Boin-zahrah) and Alborz (north Qom) Faults and seismological evidence of earthquake in the Boin-zahra areas.
Original Research Paper
M Najafi; A Yassaghi; A Bahroudi
Abstract
Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels ...
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Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels on structural style in the Central Zagros folded belt. Seismic interpretation indicates that the Miocene Gachsaran Formation forms a major median detachment level decoupling fold geometry in surface structures from Pre-Miocene units below it. In addition, the Infra-Cambrian Hormoz salt or equivalents decouple the folded sedimentary cover from basement. To evaluate the significance of multiple detachment levels, a scaled analogue model was set. Two layers of silicon putty, with thicknesses equal to 15% of total cover thickness, were placed at the base and in the middle of sedimentary cover. The rest of the sedimentary cover was simulated using dry loose sand. The result of modeling supports seismic interpretation of the Central Zagros proposing that thick middle detachment layer totally decouples structural style at surface from depth. However, the open synclines with long wavelength and low angle thrusting are developed at surficial levels, and duplex thrust systems are formed between two detachment levels. Therefore, the role of ductile detachment levels should be obtained before exploring deep hydrocarbon targets in the Zagros fold belt.
Original Research Paper
H Mardomi; B Oskooi
Abstract
During this project we tried to show high capability of the SIS scheme for 1D magnetotelluric (MT) sounding data inversion. The scheme transforms the nonlinear problem of estimating layer resistivities and thicknesses into a linear problem of estimating the coefficients of power series of the new response ...
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During this project we tried to show high capability of the SIS scheme for 1D magnetotelluric (MT) sounding data inversion. The scheme transforms the nonlinear problem of estimating layer resistivities and thicknesses into a linear problem of estimating the coefficients of power series of the new response function. We have used this scheme for prospecting conductive structures in southeastern shore of the Caspian Sea. This area is located in the GolestanProvince in northeastern part of Iran at the border with Turkmenistan. Detecting conductive sediments in this area, which are supposed to bear iodine is economically of interest. We provided data from three MT sites and inverted the data by the SIS scheme. According to our results there is a conductive layer in the depths deeper than 600 m at all three sites. We have compared our results with the previous results, also compared the results with the geological witnesses, which accordingly existence of a conductive layer has been proved at about 700 m depth. This conductive layer is proposed to bear iodine in economic meanings.
Original Research Paper
M.R Asghari; M Moktari; M Arian; M.R Vanaki
Abstract
This study has been done on “Ferdowsi” oil field, which is located on Persian Gulf. The geological studies show that the north slope of the field is situated along the Arabian shield in which its structure has been affected by the salt mass. The Fahliyan formation is the main reservoir in ...
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This study has been done on “Ferdowsi” oil field, which is located on Persian Gulf. The geological studies show that the north slope of the field is situated along the Arabian shield in which its structure has been affected by the salt mass. The Fahliyan formation is the main reservoir in the field. In order to interpret seismic data, firstly by using sonic and density logs, synthetic wavelet was constructed and compared to pseudo 3D seismic data using software. Then, formation tops were picked, and time and depth maps were prepared. Acoustic Impedance pseudo 3D volumes were performed by preparing seismic inversion. It is to note that seismic attributes help greatly to estimate reservoir properties of target formation and it is useful in better identifying the reservoir and drilling wells with reduced cost impact. In addition, in this study, faults and stratigraphic features (such as channel) were recognized by seismic attributes that is important for development of the field.
