Source Characteristics of the 2012 Ahar-Varzaghan Earthquake

The August 11, 2012 Mw 6.4 earthquakes in northwestern Iran occurred as a result of oblique strike-slip faulting in the shallow crust of the Eurasia plate, approximately 300 kilometer east of the plate boundary between the Eurasia and Arabia plates. The seismotectonics of this region is controlled by the collision of the Arabia and Eurasia plates;at the latitude of the earthquakes, the Arabia plate moves almost due north with respect to the Eurasia plate at a rate of approximately 26 millimeter per year. Over the past forty years, seven earthquakes of Mw 6 or greater have occurred within 300 kilometer of today’s events. The nearest was a Mw 6.1 earthquake in February of 1997, approximately 100 kilometer to the east, which caused 1100 fatalities. The studied area encourage the authors to determine the focal mechanism, source time function and sub events’ features which can guide us to reliable judges.

Paleoseismological Analysis Along the Astara Fault System(Talesh Mountain, North Iran)

The Astara Fault System（AFS） is located in the northwest Alborz, east of Talesh Mountain（TM） and west of the South Caspian Basin（SCB）. The AFS is one of the basement rock faults in Iran that is heavily involved in seismotectonic activity of the Talesh region, and to which subsidence of the SCB is attributed. There is little information available concerning previous AFS seismic activities and its properties. In order to elucidate the seismic behavior and activities of the AFS, we conducted a research study on paleoseismology of the fault. Based on paleoseismic evidence, two scenarios could be taken into consideration, one of which has three and another has four seismic events with magnitudes Mw in the range of 6.7 to 7.2. Evidence of these seismic events is within sedimentary succession as they have occurred during the past 3 ka（this age is determined based on the deposition rate of the region）. Six carbon samples were taken for C^14 age determination tests, the results of which clearly demonstrated that the EvIV（scenario A） and EvⅢ（scenario B） had occurred before 27,444 cal BP, while other events occurred in the time period between 27,444 cal BP and 3 ka ago. If we consider the occurrence of three or four seismic events（based on the two scenarios） to be between 27,444 cal BP and 3 ka ago, the average recurrence interval is 7,119 ± 1,017, but evidence for these events has been removed. If we assume EvI to be the youngest event（in both scenarios）, the minimum elapsed time is therefore 3 ka.

Determining the Critical Depth of Excavation and Investigating the Effect of Fault on the Resistance of Tehran Alluvial

In this paper, the effect of the burden of neighboring buildings on the stability of holes in a part of coarse-grained alluvial deposits of northern Tehran has been investigated. For this purpose two numerical and partial equilibrium methods have been used with FLAC and SLIDE software. As, the holes in the study area to the depth of 20 m in the without load state of the neighboring building and the building load of the 5-floor building in a distance of 3 meters from the depth edge were analyzed, and the results were compared and finally using the SLIDE software the guardian structure for deep recessed excavations was suggested which with this proposed guardian structure a high reliability coefficient of 1.5 can be achieved.

Assessment of Beshagard Mountain Tectonic Activity (South of Jazmurian Depration) Application IRAT Index

Morphometry status of tectonic active areas around the Beshagard mountain is as a result of the interaction of neotectonic movements, erosion and subsidence processes. Bashagard mountain contains two attached mountains (GhaleTohi imountain and Bashagard mountain) with an altitude of 2000 meters at the south of the Jazmurian subsidence surrounded by Quaternary and Neogene. The boundary between the north Makran and Jazmurian subsidence is a fault that located between Band-e-Ziarat unit and western alluvial fan and units of Ganj, Mokhtarabad and Rameshk in the south. Tectonic activity has a significant impact on their morphometry status and drainage basin system. We studied geomorphological patterns of drainage and mountain fronts features for clear changes and high style of mountain. In this study, we studied seven geomorphological indicators for each basin including Vf, Bs, Smf, Sl, Af, RA, Hi between west and south mountain front of Jazmurian. Morphometric indexes were divided in three categories. The average of seven indicators is an index of relative tectonic activity (IRAT). The level of tectonic activity of each IRAT category was determined. Finally, tectonic activity was evaluated for each drainage basin. Results show good similarity between IRAT category and ratio of tectonic activity of the number of drainage basins. The streams profile shows the uplift movement in the western part of subsidence Jazmurian. Thus, the achievements obtained from the analysis of topographic indices, the region’s river system and geomorphological evidence show the movements of uplift and movement of right-lateral strike-slip of Jiroft fault in the west and reverse faulting of Kranj and Jazmurian faults at east of subsidence Jazmurian that all indicates the diagonal tectonic movements.

The Role of Faults on Tehran Alluvial and Its Impact on Resistance of Alluvial

Tehran is located in the Alborz’s mountain range subsidence and alluvial deposits which are formed in the different faults. Though these faults caused changes in Northern Tehran’s alluvium. The geomechanics factors on these alluviums made northern area of Tehran a dangerous place to construct. In this article we have tried to determine the zone’s resistance [1], critical depth in excavation and in the end the role of faults in mechanical resistance of alluvium by comparing several pits in the zone of fault or the zone with no fault. For this purpose, the impact of the neighboring building on the pit stability has been investigated in several locations in some part of coarse alluvium of northern Tehran. So engineering methods such as numerical method and limit equilibrium with the help of software like FLAC and SLIDE were used to determine alluvium’s resistance and the critical depth of excavation. It was done in a way that several pits were analyzed and evaluated in the studied area to a depth of 20 meters in the unloaded state of the neighboring buildings, and once even the load of a neighboring 5-storey building placed at a distance of 3 meters from the edge of the considered pit was analyzed and the results were compared.