مجله زمین ساخت
پیاپی 3 (پاییز 1394)

In this study 3 major segments of the North Tabriz fault, northern, central and southern parts, were selected to analyze the seismic potential of the fault. For this purpose earthquake data since 1900 to 2014 from the Institute of Geophysics of University of Tehran and its local station, Tabriz seismological centre, Was prepared. Therefore data bank including 2850 earthquakes, for fault zone was obtained. Then, by method of Knopoff, foreshocks and aftershocks in data catalogue were omitted to have single and independent events. Then Seismic parameters include, rate annual event, activity and probability return period of earthquakes for  period of 50,100 and 475 years in terms of magnitude for 3 major segments of North Tabriz fault by Kijko method were analyzed. Finally results for three segments were compared in probability return period of earthquakes for central, northern and southern segments to obtain differences. Analyses results of this research have shown return period for destructive earthquakes of Tabriz fault (for magnitudes 6 to 6.5 in Richter scale) is 475 years.

Abstract The Qaleh-Sorkh Fault with N-S trend, 57 km length and right-lateral strike-slip Mechanism is one of the seismic and active faults in north of Sistan suture zone. Combining data obtained from satellite imagery, geological maps, shaded rather elevation model and field observations use for morphotectonic investigations in this fault, which shows quaternary sediments cut, bend or move the direction of streams with right-lateral component. Until now has been reported numerous disasters historical and instrumental earthquake in east of Iran. So, morphotectonic and paleoseismology studies have been important role in the provider of the seismotectonic ‎models. According to this, determination of seismic parameter and seismic action in the Qaleh-Sorkh fault needed to do paleoseismologic investigation. So, this fault site locate selected in 33°32’40” Latitude and 59°59’25” Longitude that has named Jannat-Abad site. In this location excavated one main trenching with 21 m length, 4.5 m depth and N80°E trends and two secondary trenching for more evidence. Preliminary results on main trench of Qaleh-Sorkh fault in Jannat-Abad site show at N7°W, 72°E in this faults that have a right-lateral slip with thrusting component.

At the northeastern margin of the southern part of the Sanandaj-Sirjan Zone (SSZ), northeast of Sirjan, two metamorphic assemblages belong to the SSZ’s basement exposed. The first complex is ZardKuh and the next is Hossein Abad-e-Souch which is situated in the north and east of the city of Balvard, respectively. The two metamorphic complexes underwent the greenschist and amphibolite facies, juxtaposed few different tectonic units such as the Dehshir-Baftophiolitic mélange and the Sardooieh volcanic assemblage, and were thrusted over the Neogene deposits. These complexes have preserved the deformational history of the region much better than the other tectonic units. Field studies accompanied by oriented sampling as well as micro-tectonic investigations provide us the role of four deformational phases in the tectonic evolution of the studied area. The first two phase of the D1 and D2 are characterized by the remnants of micro- to meso-scale isoclinal folds. Inasmuch as the whole of the metamorphic rocks were recrystallized, therefore, both of these deformational phases must be happened before or at same time as the Jurassic or older metamorphic event/s. A widespread, post-metamorphic, plastic deformational phase (D3) was occurred in the entire metamorphic rocks and part of the non-metamorphic rocks of the region. This mylonitic process of rocks may be originated in an extensional tectonic event and associated Eocene magmatism. Subsequently, another transpressional tectonic regime linked to the Arabian-Eurasian collision was the main responsible of the brittle fractures and micro-faults in the complexes; this could be synchronous with the thrusting of the metamorphic rocks onto the Neogene sediments.

For assessment of validity of extracted lineaments by Remote Sensing techniques, these structures compared with other structures which either prepared & proven by field surveying or extracted from available geological maps. Therefore, the Northwestern part of Sanandaj-Sirjan zone, which has structures with different sizes, is selected as a case study. In this research, firstly, the lineaments were extracted by compilation of semi-automate Remote Sensing Techniques. In follow, the surveyed faults were prepared by field investigations and then, the other type of faults were extracted & digitized from available geological maps and finally entered as fracture vector layers in GIS environment. These layers were overlaid by using of GIS capability and then the visional comparison was carried out for investigation and assessment of validity of extracted lineaments by Remote Sensing techniques. The results of this research shown that only main and major extracted lineaments were valid and trustable, whereas, the small lineaments have no this validity, and these outputs will be must check & calibrate by carefully field investigations.

Abstract In south of Tabriz, the Tertiary volcanic rocks have exposed in Oligocene-Miocene sedimentary deposits. The Sahand volcano is located in the NW of Iran. The volcano is stratovolcano and is dominated by pyroclastic materials and lava flows in the Miocene-Quaternary. The last eruptions included subvolcanic and volcanic domes with dacitic to rhyolitic composition. These rocks have petrological features including sieve texture and zoning in plagioclases. Common features in the young subvolcanic and volcanic rocks of the Sahand are abundance of plagioclase and amphibole, enrichment of Ba, Rb and Sr and negative Nb and Y anomalies in primitive mantle normalized multi element diagrams and enrichment of LREE relative to HREE in chondrite-normalized REE patterns. These characteristics and the location of the rocks studied in the Y-Sr/Y diagram implying adakitic composition for these rocks. Adakitic rocks of the Sahand are high SiO2 Adakitic rocks. These rocks have been derived from partial melts of garnet-bearing crustal sources (thickened lower continental crust or oceanic crust) and underwent magmatic evolution during their ascent. The formation of  studied rocks have been related to the Arabian-Eurasia collision zone.

Abstract The study area is located between high Zagros and S-S zones. The main Stratigraphy units in the study area are comprised of Volcanic-Sedimentary Sequence, Mesozoic and Cenozoic limestones. The main structures in this area are oriented in NW-SE, to the main Zagros thrust direction. Most of radiolarites have sharp hinge, chevron folds and their interlimb angles are about 30° - 70º. In Shahabad olya area radiolarites have been strongly folded and faulted in which faulting happened after folding. These radiolarites do not have an interface and they show refolding evidences. Accordingly, it seems that in this situation radiolarites are klippe. Mesozoic major foldings (in limestone) have a rounded hinge and NW-SE direction, but in some folds the evidences of refolding are visible. Cenozoic foldings of this area have rounded hinge and their interlimb angle is 120°. Also, according to ((Π diagram, most of these foldings are cylindrical with NW-SE axial surface direction. Elements of fold in these units are different so that reasons are differential rheology and formed folds in different tectonic phases. Mesozoic limestone are thrusted on ophiolites is a reason for formed duplex structures.Study of calcite twin morphology and grain size recrystallization demonstrate that deformation condition in this area have intermediate deformation zone peroperties and deformation temperature reduces from outer part to inner part. The average amount of flow stress is 200 to 300 Mpa.

Abstract The Qaemyeh area is located in 100 km west of the Shiraz city and 40 km north of Kazerun city. The Qaemyeh fault was formed by segmentation of the Kamarij fault as part of the active Kazerun strike-slip fault. This fault is part of the Zagros Foreland Folded Belt. The study area includes the normal component of dextral strike-slip fault cut the Gurpi, Pabdeh and Sarvak formations, and the other right- lateral strike- slip fault cut Asmari formation. The fault is low angle Riedel shear fractures that follow the pattern of the Kazerun fault. Analysis of the slicken lines of the fault plane were preformed in order to reconstruct the orientations effective stress by using fault-slip graphical inversion method. The  calculated plunges and trends of the principal stresses  of the normal fault are σ1 76º, S71°W,σ2 06º, S60°E and σ3 is70º, N31°E, 70º and  for the strike- slip fault, σ1 are  NE, N31°E, 07º ,σ2 is SE, S84°W, 70º, and σ3 S60°E, 06º respectively. Based on the study of fault-slip data and slickenside lineation, using the multiple inverse methods, two phases of stress are recognized. An early tension stress field caused faulting in the area, while the later stress phase is resulted by occurrence of young fracture system in the area. The tectonic regime of prevailing in the region by ratio R= (σ2-σ3)/(σ1-σ3) is extension. The stress field around faults is related of the Kazerun fault activities.