Journal of Seismology and Earthquake Engineering
Volume:23 Issue: 2, Spring 2021

This paper aims at implementing and introducing the use of conditional mean spectrum (CMS) as the main input parameters in the practice of seismic safety evaluation in Zagros, instead of the used uniform hazard spectrum (UHS). The CMS has been proposed as an alternative to the UHS to be employed as a target spectrum in ground motion record selection. The CMS provides the expected response spectrum, conditioned on occurrence of a target spectral acceleration value at the period of interest.For this purpose, a procedure for M-R-epsilon seismic hazard deaggregation in Zagros was first developed.The results indicate that by selecting high periods as the target period, the difference between the uniform risk spectrum and the conditional mean spectrum increases. So the shape of the conditional mean spectrum is more sensitive to tall structures. In fact, the shape of these spectra is highly dependent on the target period. This point is more important in the dynamic analysis of structures with several degrees of freedom. Because in these structures, considering only one period of target rotation, results in downstream results. In the conditional mean spectrum, the closer the two cycles are to each other, the higher the correlation of the epsilon values and the less scatter. This means that the farther apart the two rotations are, the less similar the spectral acceleration values are to each other.

The study of seismic stress structure in subduction zones is done from two viewpoints: vector quantity study (purpose of the present study) and numerical quantity, which are important topics in seismology. The structural zone of Makran with the main structure Accretionary Wedge is a kind of incremental wedge that is located in the hangingwall of a shallow subduction zone. In this study, earthquakes from the Harvard University Seismic Catalog (CMT) were used with magnitudes equal to or greater than 5. The simultaneous inverse solving algorithm several earthquakes were used and the stress field for different zones was calculated by inversion method. Results of stress field analysis in Makran zone and Makran-Zagros transition zone, Show heterogeneous stress fields throughout the regions. Makran zone was divided into 9 separate units based on structural morphology and seismic clusters.Stress field for each zone calculated by the inversion method presented by Michel in Zmap software.The seismic activity of Makran zone and the border between Makran and Zagros zones show higher concentration in several areas, which is probably due to the complex behavior of faults and the interaction between fault systems in this area. Large volume of seismic activity On both sides of Makran and The place of conversion of the compressive mechanism of the faults (in the fold and thrust sections) to strike slip is concentrated.Another group of earthquakes occurred at the intersection of fault systems in the center of Makran and between Jazmourian and Mashkel depressions, which shows the structural complexity at the junction of Sistan suture with Makran thrust systems.

The plate tectonics of Northeast Afghanistan are complex with diffuse and sparse seismicity in the broad plate deformation zones embedded by a number of micro-plates in the Badakhshan. Geothermal techniques in this area provide an important tool for investigating plate tectonic kinematics and identifying the approximate plate tectonic geometries. In this paper, we have processed Seismic centers data (1909–2022) collected by EMME and USGS catalogs and Geothermal data by Landsat 8 satellite images. Modeling of tectonic lines by geothermal energy and seismicity trends are studied. We find that the deformation in Northeast Asia can be well described by several blocks, independent of the Eurasian plate motion. Landsat images showed the important geothermal lines with medium and low importance. Tectonic micro-zones were defined by placing lines of high importance and medium importance together. According to the trend of seismicity centers concentrated from east to west of the Badakhshan region, the e result shows the continuation of east-west fractures. This east-west trend in the center of Badakhshan is located exactly in the fracture and the edge of the micro-zone plate with medium importance. The transformation of medium-importance fractures into high-importance fractures in the geographical center of Badakhshan can cause more important earthquakes in the region.

Seismic behavior of earth dams is significantly influenced by the nature of input motion. The implementation of identical motions at the base of the dams can yield unconservative dynamic responses. Therefore, spatially varying earthquake ground motion (SVEGM) should be considered in their seismic response analysis and design. This paper presents the nonlinear seismic analyses of earth dams subjected to SVEGM using finite difference method. Different models of earth dams are considered for this purpose. These models are different in dam height and foundation length.Different methods are available for the generation of SVEGM. A computer software is used for conditional generation of SVEGM input motion. For unconditional case, SVEGM is generated by a computer code developed in the present research based on spectral-representation-based technique. Two different coherency models are used for the generation of SVEGM. Results are expressed in terms of peak accelerations along the dam height and horizontal and vertical displacements of dam crest. The results indicate that generally the uniform input motions can produce higher values of peak accelerations along dam height and dam crest horizontal displacement than SVEGM excitation. However, the crest vertical displacement of smallest dam obtained by SVEGM input analysis is higher than that calculated by using uniform input analysis.

Today, many strategies have been proposed to improve the behavior of tall buildings under seismic load. Drifts, torsion, and structure period are essential parameters affecting high-rise building behavior. In addition, the stress concentration at the end wing of shear walls is another critical subject in high-rise buildings, which was resolved using end shear walls. The end shear wall connects the end of two shear walls in high-rise buildings without opening. In this study, a new end shear wall connects the end of shear walls in a high-rise building with regular openings (ESWO). Therefore, two 30-story RC buildings with and without end shear walls with opening were modeled by a nonlinear time history analysis under seismic load. The drift was decreased by 49% in a 30-story building with a new end shear wall. Moreover, the residual displacement of 30-story buildings with end shear walls with opening was decreased by 67%.. The time history nonlinear analysis investigation indicated that the end shear walls with opening declined the maximum displacement by 62% in tall buildings by Open Sees software. The reduction of the standard deviation of data increased the confinement in 30-story drifts in the X and Y directions by end shear walls with opening. Based on the results, the performance of the end shear walls with the opening was appropriate in the seismic behavior of high-rise buildings.

Tehran, the capital city of Iran, is a dense city with a more than 12 million dynamic population. The city is located next to the seismically active zone of the Alborz Mountains, with many active faults surrounding it. Because of Tehran's significant economic and political function at the national level, earthquakes in this city or its vicinity could largely affect the whole country. Together, these factors can explain how important the identification and assessment of seismic risk in this city can be. In this study, an OpenQuake-engine has been employed to quantify the earthquake risk of one of the districts of Tehran. Initially, a probabilistic hazard assessment was carried out for Tehran; then, after disaggregating the result of a 475-year PSHA, the main contributing earthquake scenario was determined as the hazard input. In addition, an exposure model was developed for the residential buildings of the study area, indicating building typology and locations. Further, a set of fragility and vulnerability functions that are consistent with the exposure model was selected from past studies. Finally, the seismic loss for residential buildings in district 2 of Tehran municipality was assessed in the event of the 475-year hazard scenario. The results show the intensity and spatial distribution of damages and losses in various subdivisions of the study area. Such analysis can provide essential information for disaster management decision-makers to prepare for possible future events.