TECTONICS
Year:2018 | Volume:2 | Issue:7|Papers Count:6

The NesaAnticline located in the southern part of the central Alborz is bounded bytheTaleghan Fault to the North andby theMoshaFault to the South. Unlike the wes tern and eas tern part of the Alborz range, in Central Alborz, the Evidence of Eo-cimmerianEventhas shown as extensional event. In this s tudy, evidence on development of growth s trata in the NesaAnticline which can be considered as a s tructural evidneceon the performance of the Eo-cimmerianevent in Central Alborz is presented. Inves tigations ofcross sectional mappingacross the NesaAnticline indicate a decrease in the thickness of the Triassic ElikaFormation in the anticline hinge area due to development of growth s trata. Thisrepresentsynchronous deposition of the Elika Formation and growthof the anticline. This simultaneousfolding and sedimentation is analysed to the effect of the Eo-cimmerianeventin the s tudy area andtheCentral Alborz.

Yamchi dam was cons tructed (and operated) on Balekhli-Chay river in 2005 in south of Ardabil. In order to inves tigate of effect of reservoir impounding on seismicity rate changes of dam area (30 km radius) and proving of Reservoir Induced Seismicity, firs tly, geological s tructures were determined and surveyed and then, the their Quaternary and Recent activities documented. Then, the earthquake catalogue was completed and his torical and ins trumental seismicity were inves tigated. Finally, the completed magnitude and b-values were calculated and then, impounding of reservoir effect of seismicity rate changes s tudied. The results shown that two main Ardabil and Sarein faults, with Quaternary and recent activities located in 30 km radius of dam site and many of earthquakes taken placed in cross cut of these faults. The his torical and ins trumental seismicity s tudied demons trated this area has potential of occurrences of earthquakes with 6. 1

The s tudy area is located in central part of the Urumieh-Dokhtar magmatic arc and the southeas t Ardes tan area. Eocene volcanic rocks units with a combination of andesite and basaltic andesite cons titute the mos t extensive rock units in the s tudy area. These units are hos t to Ag-Cu and Au mineralization and alteration zones. Utilization of remote sensing methods especially composite pseudo color and Filters helped us to obtain valuable information on alteration zones, exis ting brittle s tructures and the role of Zafarghand fault in controlling alteration zone. The dis tribution pattern of the faults on processed satellite images, shows three generally orientations, changing in fault orientations, the density of faults in the north of the area and positive flower s tructure. Two different patterns of alteration zones are observed including propylitic alteration and zones of secondary iron oxides with large dis tributions around copper veins and argillic-sericitic alteration zones with limited and linear dis tributions around quartz veins. Comparison of the pattern of faults, mineralization and alteration zones indicate a decrease in the degree of mineralization and increase the extent of alterations along with reducing the density of faults from north to south of the region. The Zafarghand fault has an effective role in the creation and development of alteration in the s tudy area. In this way, alteration is only seen toward the northern parts of this fault and in the southern part of this fault, no alteration effects are observed. This fault along with Kachomesqal fault has created a flower s tructurae in the area. This s tructure has created a tens tion and suitable location for mineralization and confluence of alteration zone in the south of the area.

Necessity of the human to the safe and permanent water sources is one of the important problems. In the las t decades, soft rock aquifers of country mainly are used, therefore, exploration for groundwater in the hard rocks has focused Tectonics and faults one of the important factors to crush the rocks and formations and make and develop the faulted aquifers. Therefore, in this s tudy the role of the s tructural geology is researched in development of the underground fractures and have used the geophysical tes ts to explore water sources and well locating. In this case three s tudy area researched in country. An important property means the Lambda parameter for the firs t time have used in the s tudied areas to determine the fractures density. In this research evaluate the Lambda parameter and fracture density in three s tudy area in Iran. where Lambda parameter used to determine and print the joints and fracture density and anisotropy countor maps. These maps show potentially for developing the ground water is high where Lambda parameter is highes t. Lambda was 8 in Aghlighan-chay and Khomarlou and 1. 76 in Kermanshah University. The location of the 2nd soundage in Khomarlou project after boring have had up to 40 L/S well water. Therefore this method is a new method to evalute the aquifers before borring the wells to acces the new resources of ground water and manegment the drought hazards.

The Khazar fault in the northern part of the Alborz mountains have changed the topography by making an obvious terrace in which along that the mountain drainage lines is ended where it is impossible to observe the geology s tructures due to the severe erosion and massive vegetation. The simultaneous s trike-slip and thrus t movements parallel to the Alborz mountain chain shows that the deformation in this range is the result of the oblique shortening. This deformation indicates an sinis tral transpression sys tem in the northern ridge of this mountain chain along the Khazar fault. The progressive activity of the Khazar fault has caused the fault segments, with s trike-slip mechanisms, originating from it. These faults almos t aren’ t so long and are ended to some fractures in their southern range. The northern ridge of Alborz mountain range is controlled by their s trike-slip displacement and the Khazar fault.

One of the mos t common parameter in seismic s tudies is b-value that is proportional to the relative earthquake-size dis tribution. This parameter is actually the slope of the Gutenberg-Richter law and depends on tectonics and s tress dis tribution in the region. In this s tudy, we inves tigated spatial and temporal changes of b-value and its confirmity with GPS data before and after the Ahar-Varzaghan earthquake in the northwes t seismotectonic region of Iran. The spatial and temporal changes of b-value were mapped using the Zmap software. The map of spatial changes of b-value show doublet events occurred in low b-value area which is probably s tructurally different from adjucent areas. The temporal changes of b-value also represent intense and abrupt decrease of b-value a few days before the earthquake. The time series of the GPS s tations at low b-value area showed dramatic change for a while before the main shocks. Seismic and GPS data, together, could have been considered as earthquake precursors if they had been monitored precisely and continuously. Based on this calculation, the time series of GPS data and field observations, we proposed a res training bend s tructure causing the earthquake. The proposed s tructural model can help to es timation seismic hazard risk of potential future failure area.