M Nazemi; M Qurashi; M.R Ghassemi; M Arian
Abstract
Geomorphic characteristics of alluvial fans on the sides of the ShotoriMountains in east of Tabas represent two different groups . The first group is older and is more dominant with their heads near the ShotoriMountains' hillside and their toe spreading to the central parts of the plain. These alluvial ...
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Geomorphic characteristics of alluvial fans on the sides of the ShotoriMountains in east of Tabas represent two different groups . The first group is older and is more dominant with their heads near the ShotoriMountains' hillside and their toe spreading to the central parts of the plain. These alluvial fans on which no main recent channel sedimentation is occurring, are often consisted of old alluvial sediments with a thin cover of newer ones. The second group includes younger and active alluvial fans consisted of more recent sediments of stream bed, which are located at the termination of the first group or at the southern foothills of the ShotoriMountains. It can be said that in the first group, recent active sedimentation process by the main channel has been transferred to the lower parts and toe of the alluvial fan, but in the latter group sedimentation has been done on top of the alluvial fan and on older sediments. In other words, the first group consists of two obvious old and active (recent) parts, while the second group only includes recent and active alluvial fans. Our investigations indictaes that geomorphic pattern of these two alluvial fan groups has a clear relation with location and mechanism of active faults and geomorphic surfaces in the plain of Tabas and eastern slopes of the Shotori Mountains; in other words, it is related to the mechanism of structural evolution of this mountain. According to this pattern, wherever there is the active fault of the catastrophic 1978 earthquake at the front of mountain along which the ShotoriMountains are being uplifted, the second type of alluvial fans is formed. Where the fault is located in central parts of the plain as a result of deformational front propagation, and the old part of the alluvial fan and mountain are being uplifted along it, the first type of alluvial fans (with two separate parts) is formed. This uplift is accommodated by active faulting and folding associated with bedding plane faulting. Migration of deformational front during geologic evolution of the ShotoriMountains has caused four different geomorphic levels along with three generations of alluvial fans. It is concluded that investigating on geomorphic pattern of alluvial fans will provide valuable data about the location of active Quaternary faults in alluvial plains. This pattern shows an active fault near Boshruyeh (east of the ShotoriMountains). Although no major earthquake has been reported from the fault, all morphotectonic evidences show its activity and thus the occurrence of large earthquakes in the future is expected.
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.
F. Ghaemi; F. Ghaemi
Abstract
The Northern Khorasan is one of important active tectonics area. The main faults are strike slip (dextral and sinistral) and minor faults are thrust faults. Many of thrust faults are older than strike- slip faults and some of them are younger and are active now. It is because of bending of strike-slip ...
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The Northern Khorasan is one of important active tectonics area. The main faults are strike slip (dextral and sinistral) and minor faults are thrust faults. Many of thrust faults are older than strike- slip faults and some of them are younger and are active now. It is because of bending of strike-slip faults that converts, them into thrust faults. We recognized active faults based on their characteristics. In this area we have two series of tensile joints and two series of shear joints. Principal stresses have the fallowing attitudes :() - ((
)- ). Strikeslip faults can be sympathetic. For example the 1997 Bojnurd earthquake on the Yekke-shakh fault affects Baba- aman and Gharlegh faults
M. Fattahi; S. Rostami Mehraban; M. Talebian; A. Bahroudi; J. Hollingsworth; R. Walker
Abstract
Neyshabour (approximately 200,000 pop.) lies on the southern margin of the Binalud mountains in NE Iran. The city has been destroyed four times by major historical earthquakes (in 1209, 1270, 1389 and 1405 A.D.).Three large faults occur in the region. The Binalud and North Neyshabur faults ...
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Neyshabour (approximately 200,000 pop.) lies on the southern margin of the Binalud mountains in NE Iran. The city has been destroyed four times by major historical earthquakes (in 1209, 1270, 1389 and 1405 A.D.).Three large faults occur in the region. The Binalud and North Neyshabur faults lie at the foot of the Binalud range north of Neyshabour. The Neyshabour fault lies within the valley west of Neyshabour. The Neyshabour fault, which lies 10 km south of the North Neyshabur fault, is 50 km long thrust. At each end of the Neyshabour fault two young, 10 km-long, thrust segments occur. It is close to Neyshabour city; and is a probable source of the 1209 and 1405 earthquakes. It poses a substantial seismic risk to the city because of the potential for future activity. Slip rate is one of the important parameters for seismic hazard assessment which was determined using SRTM for offset measurement and OSL for age calculation. Luminescence was measured through 7 mm Hoya U-340 filters in a Risø (Model TL/OSL-DA-15) automated TL/OSL system. The equivalent dose (De) was obtained using the conventional quartz single aliquot regeneration method (Murray and Wintle, 2000). Twelve aliquots have been processed for the sample, of which only the aliquots were accepted that satisfied the SAR restrictions. De was estimated using analyst program. Age was calculated using a weighted mean De for the sample. The Dose rate was obtained using uranium, thorium and potassium concentrations, which were measured by Micro Nomand portable gamma spectrometer in field. The results are presented in Table 1. Dividing the displacement by the minimum and the maximum ages provided the slip rate to be 0.1-0.2mm/yr.
A. Shafiei Bafti; M. Shahpasandzadeh
Abstract
According to potential of the intra-continental strike-slip faults for occurrence of large earthquakes, which are also considered as the main elements of active continental deformation, determination of their geometry and kinematics along with recognition of the active segments and temporal structural ...
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According to potential of the intra-continental strike-slip faults for occurrence of large earthquakes, which are also considered as the main elements of active continental deformation, determination of their geometry and kinematics along with recognition of the active segments and temporal structural evolution is necessary. The oblique-slip fault of Ravar with about 137 km length is extending in vicinity of Ravar, north of Kerman. In the north of study area, the fault extends parallel to the Lakar-Kuh fault, but in the south converges toward to the Lakar-Kuh and the Kuh-Banan faults. Upthrusting of the eastern block of the Ravar fault and east-ward thrusting of the Lakar_Kuh fault system constructed a positive flower structure. The motion of the Ravar fault have caused the dextral displacement and an accumulative horizontal displacement of the drainages about 940-970 in the north since Pleistocene. Regarding a minimum horizontal slip-rate of about 0.54 mm/yr, the recurrence time of earthquakes with Mw~ 6.7 would be about 1400 year. In the middle part of the fault, the Reidel fractures of R, R, and P has been well developed and caused a dextral deflection of the Esmail-AbadRiver about 16m. With assumption of characteristic earthquake occurrence, the maximum slip per event could be about 0.75 m, which is consistent with the minimum displacement of the recent gorges. The amount of horizontal dextral displacement of the fault decreases toward to the south, whereas the vertical component of the fault motion increases, so that the Pleistocene deposits show about 10 m difference in elevation across the southern part of the fault. Concerning the trend of meizoseismal zone of 1911/04/18 Ravar earthquake (M~ 5.8, I0~ VIII) and parallelism of trend of the co-seismic surface rupture (N13W) with the southern part of the fault, the Ravar fault could be responsible of this earthquake. In addition, the active cross-faulting of the Dehu, the Dehzanan, the Chatrud, the Pasib, and the Darbid-Khun control the recurrence time and magnitude of the earthquakes in the study area.
