جستجوی مقالات مرتبط با کلیدواژه "tectonics" در نشریات گروه "زمین شناسی"

Ten tectono-sedimentary basins have been identified around the Paleotethys suture zone in NE Iran. These basins have been developed from the Lower Paleozoic to recent time in response to relative movements of the of Eurasia and Gondwana supercontinents. The recognized basins from ancient to modern are: 1) Paleozoic passive marginal basin of central Iran, 2) Devonian-Carboniferous platform basin of Turan plate, 3) Active continental margin basin (trench and foreland), 4) Permo-Triassic arc-related basins, (5) Upper Triassic-Lower Jurassic peripheral foreland basin, 6) Lower to Middle Jurassic intramontane basin, 7) Middle Jurassic rift basin, 8) Oligocene-Pliocene foreland basin and 10) Post orogenic molasses basin. Each basin has its own characteristics, and is formed in different tectonic setting during the evolution of the Paleotethys Ocean in NE Iran.

Hassanabad-Shojaabad region is located in Urmia-Dokhtar magmatic belt. Regarding the formation of this area, two theories of rifting and subduction have been proposed. In this article, data obtained from desert, petrography, geochemical and magmatic tectonic studies were combined and analyzed. Using several geochemical and magmatic tectonic charts, the type of rocks in the region and the magmatic series of intrusive and volcanic rocks were determined. The intrusive and volcanic rocks in Hassan Abad region are of calc-alkaline type and the result of subtraction of basic magma with the origin of lithospheric mantle, these rocks belong to the subduction tectonic environment in the final stages of expansion of Komani Island. Volcanic rocks and intrusive masses in Shujaabad area are of shoshonite type and are the result of tonalitic melting of the lower crust, these rocks belong to the tectonic environment of the continental arc margin. Therefore, the area under study has been inclined to pressure at the edge of subduction and back arc areas, where Hassan Abad is located in the area of the edge of subduction and Shoja Abad is located in the back arc area.

Qeshm Island, with an area of ​​1,486 square kilometers, is located at the southeastern end of the Zagros Belt and at the western end of the Strait of Hormuz. Since the tectonic era, it seems possible to assess the influence of neotectonics and fault dynamics on island morpho-tectonic deformation using basin tectonic indicators. In this research, five indicators are extracted and calculated using satellite images, geological maps, aerial photographs, and a digital elevation model (30 meters) using various software. The smoothness and asymmetry of waterways (AF), watershed shape index (BS), cross-topographic symmetry index (T), river meandering index (S) and their comprehensive evaluation are evaluated in model form (IAT)). It is an index to evaluate the degree of tectonic deformation in the basin, and the obtained results indicate the relative dynamics of various tectonic deformations on the island. Furthermore, based on the IAT index, 26 of the 44 subbasins belong to a very high tectonic layer, consistent with the number of faults, so more active tectonic deformation is observed in the western part of the island.

The purpose of this study is to evaluate the tectonic activity of the region between Zarab fault and Zagros main reverse fault (using geomorphic indexs). There are two main reverse Zagros faults and Zarab fault in this region. Hypostometric integral index (Hi), asymmetry drainage basin index (Af), Stream length-gradient index (SL), mountain front sinusitis index (Smf) and relative activity tectonic index (Iat) were used. The results show that the values of geomorphic indexes and geomorphic evidence indicate different relative activity in some parts of the region. Zarab faults and the main inverse Zagros fault of alluvial and alluvial sediments as well as large rivers of Nal Ashkanan and Dasht e Zarrin play an important role in the geomorphology and tectonics of the region and the relative activity of the region. Rivers and drainage networks are among the most important features that are very sensitive to tectonic change. According to the obtained relative activity zoning map, it can be said that the study area has moderate to very low relative activity

Nazi salt dome is located in the border of high Zagros and folded Zagros in the northwest of Chaharmahal Bakhtiari province. This dome is affected by Zardkooh fault in the heights of Zard Kooh. The sequence of formations in the region includes Infra-Cambrian sedimentary rocks up to the present time The aim of this study was to investigate the active tectonics associated with Zardkooh fault and Nazi salt dome in Bazaft area in Chaharmahal and Bakhtiari province, using morphometric indices. Zardkooh fault is the border of high Zagros and folded Zagros. Zardkooh fault and Nazi salt dome are both exposed on the ground. In order to study the tectonics of the study area, the study area was first divided into 59 basins Then quantitative morphometric indices such as hypostometric integral index (Hi), drainage basin asymmetry index (Af), river gradient index (SL), basin shape index (BS), mountain front sinusitis index (Smf), relatively active tectonics index (Iat) has been calculated. In Hi index, 7 basins with active new tectonic activity, 21 basins with moderate tectonic activityand 31 basins with low tectonic activity were identified. Also in Af index, 18 basins with high and activetectonic activity, 21 basins with medium tectonic activity and 20 basins with low tectonic activity were determined. One high-activity basin, two basins with moderate tectonic activity and 56 basins with low tectonic activity were identified in the SL index. In BS index, 2 basins with active tectonic activity, 2 basins with moderate tectonic activity and 54 basins with low tectonic activity were identified. In Smf 16 index, the basin has active tectonic activity and the rest of the basins have low to very low tectonic activity. Relative activity index (IAT) in the study area indicates the presence of 3 basins with active tectonic activity, 26 basins with moderate tectonic activity and 30 basins with low tectonic activity are low. Based on the calculated indicators, the study area has different basin activities from medium to low. The data show that the activity of Zardkooh fault, the activity of the Nazi salt dome, large waterways in the region, and vegetation in the region have a significant impact on the activities of the region. The area has moderate to low new construction activity.

Geomorphic indices are major tools to recognize tectonics activities.
These indices have the advantage of being calculated from Arc GIS package over large areas as reconnaissance tool to identify possible geomorphic anomalies related to active tectonics.
In this research, Karkheh river basin was selected and six geomorphologic indices; drainage basin asymmetry (Af), stream-gradient index (SL), drainage basin shape index (Bs), mountain-front sinuosity index (Smf), valley floor width-height ratio (Vf) and hypsometric integral (Himatter) were calculated. Then, the values were classified in three groups and analyzed. The area of the three class as follows:Class2) 12180 km2, 23.7%
Class3) 32318km2, 62.9%
Class4) 6843km2, 13.3%
The region has an area of about 51341 km2, so this result presents the moderate relative activity in the extensive parts of the area.

It is very important to use geomorphometric indices to detect active tectonics. The parameters related to the drainage network are the angle of connection of the rivers. And quantitative assessment can help to identify the active tectonics, earth science researchers. Kopet Dagh -Hezarmasjed Geological Unit and Aladagh - Binalood is one of the most active geological units in Iran. In this research four basins were selected to evaluate the role of tectonics in the cross-flow angle of the rivers.Baghrood and Bojan Basin in Aladagh-Binalood Zone and Zavin and Sharrood Basins in Kopet Dagh -Hezarmasjed Construction Zone .In this way, were used cross-flow angle (CA), branching index (R), basin asymmetric percentage index (PAF) and mountain front elevation index (Smf).Also, cross-flow angle calculation showed that the highest amount in Zavin watershed is 73/67 degrees and the lowest amount in Baghrood Basin is 59.5 degrees.Which indicates changes in the flow paths of the streams, such as the capture of the river and, consequently, tectonic movements in the slope Khor anticline.Also, the calculated values of (R) (Smf) and (PAF) indicate that most tectonic species of Kopet Dagh basins are compared to the Binalod mountain basins.

Morphotectonic is the study of shapes and forms that evolved on the Earth's surface caused by tectonic. Binalud thrust fault along the east-west fault Nishabor, caused fundamental changes in the longitudinal profile of the region's rivers. In this study, we used indicators of geomorphometry of catchment and drainage network, including index, serration mountain front Smf, the gradient of valley-Sl, symmetry index topographic cross T asymmetry index rivers in the catchment area AF, the shape of the basin BS, and including geomorphological studies in five basins Baghrod, Bojan, Kharve, Darrod and Gorin. Topographic maps, geology map, aerial photographs and digital elevation model and ArcGIS 10.1 were used for analysis of regional tectonic geomorphology. The results confirm the southern slopes of Binalud uplifted due to subduction thrust fault West ward, is tectonics. According to Review done Check out the 5 selected watershed basins by Baghrod and Bojan tectonically more active the Gorin and Kharve are more active than the rest of the studied areas.

Seismic values are the main parameters in evaluating the neotectonic activity of a region. In August 11, 2011, two Mb=6.4 and Mb=6.3 earthquakes occurred in Ahar-Varzaghan region within 11 minutes. Seismotectonic investigations imply that the faults generating the events are the young faults of the regions. Also, distribution of the epicenters represent a pattern consistent with the fault trends in the area. Temporal and spatial distribution of the earthquakes (fractal analysis) as earthquake pre-indicators together with a-b values were used toassessthe neotectonic activity and explore the seismic model of the Ahar area. Results showa sharp decrease in b-value,indicating that the main shock was associated with a zone of high strain rate. The seismic model presented for the Ahar area illustrates three periods after the main shock including: 1) an early quiescence Q1, 2) an aftershock period B, and 3) a late quiescence Q2. The rather increase in b-value during the Q2period is interpreted to indicate stress decrease in the region.

In the 11th August 2012 two Earthquakes trembled Azarbayjan that their scales were 6 Mw and 6.2 Mw. The locking depth of these two earthquakes is about 10 km, the epicenter of the first one is 38.55 N and 46.87 E, and the second one is 38.87 N and 46.87 E. In this research displacement of the earth crust during trembling on these stations was determined by using permanent GPS stations in Ahar Earthquake 2012. The cosiesmic offset due to the Ahar earthquake has been studied using permanent GPS Network of Azarbayjan (a sub network of Iranian permanent GPS Network). Here, we explore these issues using data processing and times series analysis of the GPS sites. We found 0.5 to 2 cm offset that the GPS site (near and far) showed from the main rapture due to earthquake.

Summary: Rapid and accurate assessment of earthquake source parameters is extremely useful in seismology from different perspectives including hazard assessment and also for rapid response services. Nowadays، there exist various automated phase detection and location algorithms that provide near real-time seismic bulletins. Such algorithms rely on explicit phase identification and complex event association techniques that must be reformulated for different velocity models accordingly. These algorithms often use only P and S phases (Withers et al.، 1999). In many cases، the signal-to-noise ratio (SNR) is small، making it difficult to use the classical methods based on phase identification. However، event location based on a migration approach has recently been proposed in seismology (e. g.، Kawakatsu and Montagner، 2008; Larmat et al.، 2009; Kim et al.، 2011; Gharti et al.، 2011) mostly because phase identification is not required in this method. Time-reversal (hereafter referred to as TR) is a migration-based approach، in which the observedseismograms are back propagated in time in order to determine the location of the events. The TR method can potentially provide more accurate information on earthquake processes especially for small earthquakes where phase-identification-based methods are hardly used due to a low SNR. In general، classic earthquake location is a nonlinear problem and linearization oftravel time equations in earthquake location is mandatory based on a Taylor series expansion around some prior estimate (or guess). The locations of events also contain random errors، for example errors associated with the arrival time، as well as systematic biases due to manual phase picking. On the other hand، the most important error in earthquake locations with the TR method is only the inherent dependence of earthquake locations on an assumed seismic velocity structure of the Earth. The history of the TR method، which takes the advantage of none-phase identification، can be traced back to automated local and regional seismic event detection and a location system using waveform correlation by McMechan (1985) and Whiters et al. (1999). In recent years، thesame theory of waveform correlation is used by various researchers to investigate earthquake location in local (e. g. Maggi and Michelini، 2010)، regional (OBrien et al.، 2011) and telesimic distances (e. g. Ekstrom، 2006; Larmat et al.، 2006) using the TR method. The time reversal algorithm has been recently used to study the location and characterization of seismic sources in elastic media. This algorithm is related to the back propagating of the recorded data in earth in reverse time to find the parameters of an event. In this study، we investigate the location of small seismic events in south-eastern of Iran in an automatic mode. Most of the events are linked with structures of east of the Lut Block occurred after the main shock on 2010، December 20 with Mw 6. 3. Data from a temporary network was used to investigate the P phase clarification using a kurtosis analysis on records and then it was migrated to the source in reversed time to find thelocation of events without human bias. We tested several time reversal imaging conditions by synthesizing events for location. Finally، we used the best obtained parameters from a synthetic test to apply the same procedure to a real database observed after the main shock in the Rigan region which had been recorded by the network. We showed that although the obtained parameters were used in the real data، simple limitations such as number of contributed station in location should be used to improve the location. The results showed that well-constrained centers of events were in good agreement with the trend and dip of faults in the region and the focal mechanism of the main shock.

Being familiar with the modes of motion and coordinate changes of the Earth surface points as a function of time is very important and essential in different types of geodetic applications. The puepose of this research is the time-dependent modeling of displacement and coordinate changes of the Earth’s crust surface points due to the plate tectonic motions and earthquakes in the region of Iranian plateau. The provided model could be used to predict the coordinate changes of surface crust points or to predict the geodetic observations (distance and angle) from one arbitrary epoch to another. This model receives the coordinates in various ITRFs or WGS84 reference frames and after the computations are made, the results could be provided in any reference frame. The Bursa-Wolf seven-parameter conformal model was used to transform three dimensional Cartesian co-ordinates between WGS84 and ITRF2000. In the absence of a crustal motion, the equations for transforming positional coordinates from one ITRF to another are rather familiar to the surveying community, i.e. it is a seven-parameter transformation. In the presence of a crustal motion, the transformation equations can be generalized to allow one frame to move relative to the other. Thus, each of the seven defining parameters becomes a function of time. Therefore, in modeling, fourteen transformation parameters were used for ITRF2000 reference frame transformation to the previous and later reference frames. Okada (1985) analytical model was used to model sudden coseismic and interseismic motions due to earthquakes. In previous works (Pearson, 2010 and Meade, 2005) the block model was used for secular and interseismic deformation modeling, but in this research, we used Okada (1985) analytical modeling for this purpose since (1) Modeling the present-day velocity field determined with GPS networks incorporates geological constraints on the geometry of the main structures and on the long-term deformations; (2) Regions between the major faults are not rigid and so the modeling allows for internal deformations. Finally, we have a tectonic model for Arabia-Eurasia oblique collision zone in Iran that is more realistic than the rigid block model. This model shows that about 30% of GPS velocity field components are produced by faults inside Iran, 60% by Arabian plate and 10% by Anatolian plate. Continuous use of GPS data and local network observations is recommended to get a more precise model for secular and interseimic motions. Also using more precise geometric faulting parameters due to earthquakes obtained by inverse problem solution based on GPS or InSAR observations is recommended to get more precise outputs. Postseimic motions were not modeled in this research since this effect is a function of time and its amplitude is just considerable for large earthquakes, beside that the amount of this effect is reduced with time. Anyway, the postseismic deformation modeling due to intense earthquakes with a large focal depth using Wang (2006) model is recommended. In this research, just the effects of secular, interseismic and coseismic motions were included in the model. To complete the model, it is recommended to consider the effects of the crustal motions associated with land subsidence, volcanic activity, postglacial rebound etc.