Journal of Seismology and Earthquake Engineering
Volume:18 Issue: 2, Summer 2016

The aim of this work is to understand the relation between time and place that an earthquake takes place. In order to answer this question, the Modified Level Crossing (MLC) technique has been implemented. By studying two earthquakes, one in Iran and one in California we came to the conclusion that there is a relation between time and place of an earthquake occurrence. As a matter of fact, this relation is quite decisive. By performing MLC analysis and comparing the two regions, we can state that geographical effects play an effective role due to geophysical differences between Iran and California. Indeed, by comparing the readings of Iran and California, one could come to understand the geophysical differences between the two domains.The so-called level crossing analysis has been used to investigate the spatial and temporal fluctuations of earthquake form time series. In this paper, we calculated the average frequency of up-crossing for original and shuffled data of Iran and California earthquakes in spatial and temporal series. This analysis showed a significant difference between the original data and shuffled data. By introducing the relative change of the total number of up-crossings for original data with respect to the so-called shuffled data, R, and calculate the Hurst exponent, Iran and California earthquakes are compared.

A web-based system is designed to evaluate and communicate the seismic risk to the public. In this context, risk denotes the mean monetary and social losses. The system aims at communicating the risk to building owners with the objective of raising the public awareness of the significant seismic risk in Iran. This is the first step towards motivating the society to take appropriate risk mitigation measures. The object-oriented architecture of the system facilitates its steady growth to accommodate more advanced risk analysis techniques. The adopted risk analysis approach is tailored to the construction quality and the seismic regulations in Iran. The system receives elementary, observable characteristics of the building as input, and interprets the resulting risk in layman’s terms. It is showcased by two real-world buildings at the campus of Sharif University of Technology, Tehran, Iran: one unreinforced-masonry dormitory and one steelbraced educational building. As an example result, the system predicts a significantly higher rate of fatality for the dormitory due to the poor performance of unreinforced masonry. The paper is concluded by explaining the ongoing research by the authors to further develop the system with more advanced risk communication techniques.

This experimental study demonstrates a novel optical method which is used as a readout system for a vertical seismometer that is, based on the moiré technique. Our purpose was to build an optical seismometer whose performance is similar to seismic sensors. The oscillation system of the sensor is a spring-suspended mass which its position is monitored by moiré technique. The maximum displacement is limited by mechanical issues to a few millimeters. We used two similar overlaid grids at a small angle that, one of them is fixed to the frame of the sensor and the other one is attached to the suspended mass. Moiré pattern is illuminated with a laser diode. The laser beam passes through the moiré pattern and a narrow slit and hits on a light detector. Due to moving the oscillatory mass and the fringes movements, the light intensity on the detector varies and is recorded as voltage. A digital signal processor samples the output voltage and produces a record of the seismometer mass displacement. The response of the optical seismometer was validated through comparison of recorded waveforms with those obtained by CMG-6TD seismometer. Comparisons with conventional seismometer show that, in terms of both noise and signal fidelity, the optical approach is quite viable. Our seismometer was found to be compatible with the reference seismometer.

In this study three earthquake-induced rock fall hazard maps of the regions affected by Varzeghan-Ahar earthquake doublet are presented. On August 11th 2012 an earthquake doublet (Mw= 6.5 and, Mw= 6.3) struck Varzeghan, Ahar and Heris regions (located in Azerbaijan-e-Sharghi province of Iran). Most of the landslides triggered by the earthquakes were rock falls and disrupted rock slides. Several rock fall zones, some with more than 150 rock falls were recorded, the farthest one approximately 45 kilometers away from the earthquake epicenters.
A landslide inventory map of the region was prepared. Three methods of Information Value (IV), Logistic Regression (LR), and Analytical Hierarchy Process (AHP) were used for earthquake-induced rock fall hazard zonation. The results from each method were then compared using Receiver Operating Characteristics (ROC) curve. The area under ROC curve (AUC) was 0.927, 0.90, and 0.898 for LR, IV, and, AHP models, respectively. The most accurate rock fall hazard zonation map of the study area resulted from LR method, and IV method is, to a small extent, more accurate than AHP.

The need for evaluation of a sound earthquake disaster mitigation and critical assessment of the detailed cumulative seismic energy dissipated in the Vrancea Region in Romania is required to identify the active seismogenic activity for the last 12 years associated within the seismotectonic zone of Vrancea Region of Romania. The seismogenic behaviour observed by the recent strain energy release from 2004 to 2016 in Vrancea by processing the energy bulletin of the seismic energy discontinuity gives new results. Vrancea is the most critical seismo-tectonic region in Eastern Europe prone to earthquakes and suffer seismic energy variations that can be linearly approximated due to the constant rate of earthquake occurrences. This allows to forecast the magnitude using iso-contour plotting and analysis of the energy-magnitude relationship. The study shows that there is an immediate need to diagnose for a unifying slip-dependent law determined from strain energy bearing capacity of the region. In this study, the average moment release rate and strain release pattern within time frame 2004-2016 for the region have been examined by analysing the updated Romplus Catalog from the Vrancea region of Romania. The study shows that if strain energy released by a tectonic block is large it might affect the stress building process in the rocks of adjacent tectonic blocks. A zone of future earthquake activity in the Vrancea based on the study is also identified and an integrated functional block diagrams as part of the activity in any geo-tectonic region incorporating pre-earthquake parameter assessment is developed.

In this paper, the nonlinear behavior of reinforced concrete shear wall with consideration of bond-slip effect between the bars and surrounding concrete is investigated. Bar and concrete stress-strain relations, the bond stress-slip relation and the shear stress-strain relation as well as their cyclic behavior including the strength degradation and stiffness degradation are adopted known specifications. In the modeling, shear wall is divided into two types of joint element and RC element. In RC element, the effect of shear deformation is considered and based on Timoshenko beam theory the effect of shear has been considered during the calculation. A numerical model based on the fiber method is used for nonlinear analysis of reinforced concrete shear wall. Separate degrees of freedom are used for the steel and concrete parts to allow for the difference in displacement between the reinforcing bars and the surrounding concrete. The effect of bond-slip has been considered in the formulation of an RC element by replacing the perfect bond assumption from the fiber analysis method. The effects of embedded length and pull-out force on the seismic behavior of a reinforced concrete shear wall were investigated. The reliability of the method has been assessed through a comparison of numerical and experimental results for a variety of specimens tested under cyclic loading. A good agreement between experimental and analytical results is obtained for both cases of strength and stiffness during the analysis.