Journal of Seismology and Earthquake Engineering
Year:2019 | Volume:21 | Issue:1|Papers Count:7

This article uses, for the first time, the absolute age for a Qanat system, to determine the slip rate of an earthquake fault. In Iran, many ofQanat galleries were dug in the vicinity of, or directly upon, active faults. In some areas such as Dasht-e Bayaz fault, line of craters are displaced by the activity of the fault, which lead to dry Qanat stream, and consequently to dig new shafts by habitants. By means of measuring the offset between new shafts and old shafts, and considering Qanat antiquity, the estimation of fault slip-rate, which is one of the prominent elements in hazard assessment, becomes possible. This study uses absolute age for a Qanat system, obtained through optically stimulated luminescence dating of grains in spoil heaps of Qanat wells. Feldspar single-grain dating of silt sediments that overlie the construction spoil show that the Miam Qanat was maintained until at least 1. 6-2. 6 ka. Combination of this age and the 10 meter displacement of Qanat line of shafts byDasht-e Bayaz fault provide a slip rate of 5. 2-4. 3 mm/yr for this fault.

IDuring large earthquakes, a soil deposit overlaying an active fault is suspected to experience quasi static differential settlement produced by propagation of bedrock fault rupturing. Such differential surface dislocations can cause severe damage to engineering framed structures. Although there is partly extensive literature in this field, in most previous studies, super structures are not considered in the analysis directly. This paper investigates the interaction of a frame structure located on top ofa soil sediment with a reverse fault rupturing. For this purpose, a series of reduced scale 1 g box tests with a steel frame structure were conducted. Then, the same related numerical models were calibrated and validated using physical modeling results. To compare different structural system behavior against surface fault rupture, two types of steel framed structure including moment resisting frame and concentric braced moment resisting frame were selected in the numerical analysis. A brief sensitivity analysis on structure position relative to fault outcrop is performed using numerical Finite Element (F. E. ) method for both types of structural systems. Different responses for sediment and structure are considered. The results showthat deformation mechanism of structural elements in these two systems are basically different. Based upon the results of this research, the moment frame is suspected to have more severe structural damage or even complete destruction.

In this paper, the surface fault displacement hazard at the Choman damis evaluated by a new approach of probability fault displacement hazard analysis (PFDHA). For this, fault map and fault characteristics of area are determined based on the aerial photographs, satellite image, and field studies. In this study, Piranshahr fault is divided into two segments of Piranshahr-Sardasht and Sardasht-Penjwen from across point of Armardeh fault. The empirical relationships proposed for strike-slip fault is applied to estimation of probability fault displacement hazard curve of Choman dam. The return periods of 10000 and 35000 years are selected for estimation of fault displacement for different earthquake design levels. Finally, fault displacement for Design Basic Earthquake (DBE), Maximum Design Earthquake (MDE) and Safety Evaluation Earthquake (SEE), 20, 30 and 65 cm are proposed.

In the seismically active zones, pseudo-static and pseudo-dynamic approaches are widely used for designing the retaining wall with c-f backfill. However, the effect of soil amplification is neglected while considering propagation of waves from base. Soil amplification is crucial in the computation of seismic active earth pressure while analyzing the retaining walls of significant height. It should not be ignored in the seismic design of retaining wall. In this paper, soil amplification effects has been incorporated in the pseudo-dynamic approach for prediction of earth pressure on inclined retaining supporting inclined c-f soil backfill. Depth of tension crack has been obtained from derived seismic earth pressure distribution for soils having nonzero cohesion. Then total seismic earth pressure is computed from integration of earth pressure from depth of tensile crack to base. A parametric study is conducted to examine the effect of various parameters like cohesion value of soil backfill, wall friction, wall inclination, soil backfill inclination, soil amplification, horizontal and vertical seismic coefficients. The results obtained for seismic active earth pressure is clearly showing the non-linear behavior behind the inclined retaining wall, which is the requirement of the design of retaining wall in earthquake-prone regions.

This paper introduces an improved isolation system for aboveground storage tanks (ASTs). In this system, the tank shell is supported by a ring of vertical isolation systems (VIS) that dampen the rocking motion of the tank shell caused by dynamic loads. On the other hand, the forces in the vertical direction caused by the overturning moment are isolated as an alternative to the common horizontal system used for shear base isolation of ASTs. The effects of the proposed vertical isolation system on the seismic responses of the contained liquid are examined using various tank dimensions and earthquake ground motions. The finite element model (taking into account fluid-structure interaction effects) is used to simulate the contained liquid, as well as the tank shell. The results indicate that the new system could efficiently reduce the main seismic design parameters of the tanks, including base shear, overturning moment, and seismic stress in the tank shell. The sloshing wave height, however, is not significantly affected.

The maximum earthquake magnitude plays a crucial role in different aspects of seismic hazard and risk assessments. Previous work by Salamat et al. [1] shows the divergence of the confidence interval of the maximum possible earthquake magnitude Mmax for high levels of confidence 1-a, in different seismotectonic zones of Iran. For this, Mmax is replaced by the maximum expected earthquake magnitude mt that is calculated for different predefined future time intervals Tf. In this work, the frequentist and Bayesian approaches are applied to calculate the upper bound of the confidence interval of mt. The frequentist confidence intervals are calculated for the level of confidence 1-a = 95% and 99%, and future time intervals Tf = 30, 50 years. In the Bayesian approach, the posterior distributions of the maximum expected earthquake magnitude are calculated for Tf = 30, 50 years and 90% confidence level. The stationary Poisson process in time and Gutenberg Richter relation are assumed as a statistical model for the magnitude distribution. In order to estimate mt in each seismotectonic zone, three different scenarios of Mmax= 8. 5, 9. 0, 9. 5 are assumed. In order to find the influence of the declustering, all calculations are applied for both original and declustered catalogs. The results show, as long as the length of the time interval is short or moderate, different values of Mmax have a minor effect on the estimation of the maximum expected earthquake magnitude mt.

At different parts of the world, there are many unreinforced masonry buildings have been constructed for different uses. Studies have shown the insufficiency in the design and performance of these buildings. Proper a modeling approach for nonlinear analyses of masonry buildings and seismic assessment of these buildings is necessary. This study presents a practical approach to model unreinforced masonry building. This approach considers the effects of including the lateral resistance of masonry walls in resisting seismic loads. The main aim of this article is showing the utility and efficiency of a simple method in the explanation of the behaviour of masonry buildings subjected to seismic loads. The simple models are essential because they provide easy and accessible understanding of the structural response. This approach was used to assess a common type of masonry building as a representative building of Iranian masonry schools. The results of static and dynamic nonlinear analyses show this approach offers a good balance between simplicity and accuracy and can be used for nonlinear analyses and seismic assessment of these buildings.