مجله زمین ساخت
پیاپی 1 (بهار 1394)

Moallem-Kelayeh Inlier is located in western north Kandovan fault zone in west of central Alborz. Moallem Kelayeh Inlier is limited by Khashchal and Ovan faults in north and south, respectively. These faults with different dip direction caused lower Paleozoic rock units thrust over Cenozoic ones. Ovan fault is deeper than Khashchal fault and it formed as hanging wall back-thrust and caused Moallem Kelayeh Inlier be considered as a pop-up structure. According to the Ovan Fault dip angle, development of its footwall thrusts and hanging wall back-thrust, hanging wall anticline and footwall syncline, exposure of the Barut Formation on its hanging wall and development of a pop-up structure, it is proposed that the  Ovan Fault was initialy normal fault reactived as a reverse fault. During inversion of the Ovan normal fault the Khashchal Fault has formed as back-thrust to the Ovan Fault.  The TF1 and Hanis thrust faults are also developed as footwall thrusts to the fault. In addition, the TF2 and TF4 thrust also formed as hanging wall thrusts to the fault. Final collision of Arabian plate-Central Iran at Miocene and ruling of dextral transpression regime caused development of strike slip faults in northern part of the study area that cut and displaced other faults. Thus, these faults are younger. Since these fault cut by Alam kuh and Nusha plutons, it is therefore deduced that these faults were not inactive during Pliocene.

Identification of the shaj seismogenic fault in the eastern Zohan 2012 earthquake(E-Iran) show that there are high-potentials of strong earthquake another faults in addition to the Abiz-Gazik-Avaz active fault system. Although seismic data are not distributed uniform across region however folding and cutting the Quaternary sediments is indicate this region should be considered as the places bearing active tectonic and high seismic risk. The process magnetic anomaly maps show magnetic lineaments with NNW (Shaj, Janahmad and Takhtejon) and E–W (Zohan, Saghdar and Qohestan) orientations.Spatial correlation of the Zohan and Qohestan magnetic lineaments with results of obtained from GPS data confirm the activity of E–W basement faults in the north and south region. This is suggested that rhomboid blocks from NNW and E–W trending resulted by the detection of topography lineaments and there are comparison with magnetic lineaments and seismogenic faults.

Relative changes in sea level and sedimentary facies are affected on lithology, thickness, porosity, diagenesis and ending surface of the sediments layers significantly, that all of them are controller factors in the fracture patterns. In this research, the relation between the fractures density and spacing with parameters such as the lithology and thickness of the Cretaceous sedimentary units in two regions of Dizlu and Kolah Ghazi of Isfahan, have been studied. Identification fracture systems using satellite images, combination of the stratigraphic studies with mechanical and geometrical analysis of the joints through the linear method (using the field data perception and provided images of the study area) and statistical analysis of the fractures are the most important issues that to them has been done and discussed in this study. The results show, respectively, Dizlu and Kolah Ghazi area have five and six fracture sets and the change in spacing or density of the fractures can be affected by, thickness of sedimentary layers and type of lithology. The mechanical stratigraphy study and evaluation of the fracture properties in different sedimentary rocks, can be achieved to predictive the fracture patterns within different sedimentary units. Consequently, the knowledge and information about the storage and flow of the fluids within the sedimentary rocks in different regions improved.

Shahreza area in the central part of Sanandaj-Sirjan zone is selected as case study for verifying of this zone activity. In this research, the structures and its kinematics were determined by using of Geoinformatic techniques such as: Remote sensing, GIS and field surveying methods and also, distinguished the Neotectonic evidences of active faults and occurred earthquake foci circumstances. The result shown that the Shahreza fault (with Dextral strike-slip mechanism) and Nasrabad fault (with Sinistral strike-slip mechanism) are the main faults in this area. The Neotectonic evidences of recent activities of these faults are exhibited as: truncating of recent alluvium, influencing on sedimentation regime of rivers, faulting in recent alluvial terraces and fans and deformation of recent alluvium. Also, in intersection of these main faults, many earthquake foci were taken placed.

In this research, using data from earthquakes recorded in Central Kopeh Dagh range, by the Iranian Seismological Center  (http://irsc.ut.ac.ir), we have interpreted Tectonic of the range by calculating seismicity parameters a-value, b-value and fractal dimension. Kopeh Dagh range, is northern zone of deformation caused by the convergence of the Arabian and Eurasian plates. It forms an active tectonic zone trending northwest - southeast, on the border between Turan platform to the North and Lut-Central Iran Blocks to the south. The Map of  b-value, shows that this parameter changes between about 0.6 to 1.1, that is usually seen in tectonically active areas. The fractal dimension of region is 1.75 that expresses the complex and multiple stresses on the range. Maps of  b- value and fractal dimension of earthquake epicenters, shows a clear change in the Bakharden–Quchan fault zone, so that it can be divided into three distinct parts. Parts A and C forms the asperities and part B is located between them. The results show that using the seismicity parameters a-value and b-value, fractal dimension and  local stress distribution maps, provide valuable information about the mechanism of faults and fault systems changes over time.

Abstract The study area is located in the north of Doroh and northern part the Sistan suture zone. Volcanic rocks such as basalt, Basaltic andesite, trachyandesite and andesite  with Cretaceous age are interbeded with  sedimentary rocks. Main textures in these rocks are porphyric, glomeroporphyric, intergranular, vesicular and amygdaloidal. Plagioclase and pyroxene are main minerals in basalt and basaltic andesite and main phenocrysts in andesite and trachyandesite are plagioclase and hornblende with minor of alkali feldspar. Geochemically, these rocks have calc alkaline and tholeiitic nature and show enrichment of LREE, LILE and depletion of Ti,Nb and P that support their relation to subduction zone. Enrichment  in U, Cs, K, Sr, Zr, Th can be result of crustal contamination. This magmatism can support  subduction of Sistan oceanic lithosphere in east of Iran.