Probabilistic Seismic Hazard Analysis for Tehran and Suburbs by Using of First Order Second Moment Algorithm

Document Type : Research Article

Authors

1 Assistant Professor of Civil Engineering; Shahrood University of Technology

2 Shomal University, Amol, Iran

Abstract

One of the most damaging natural disasters is an earthquake which random process of its motions has made predicting and preventing its occurrence impossible, but it is possible to reduce the probable damages caused by earthquakes through probabilistic seismic hazard studies. Iran is one the countries that always has been exposed to the damages of this natural phenomenon. The experiments of many countries that are at high risk of earthquakes, has shown that damages can be reduced when seismic hazard analysis is achieved in structural design process. Seismic hazard analysis requires the earthquake data and obviously more accurate data can lead to results with more precision. The magnitude, location and focal depth of the earthquakes are the most basic data that needs to be updated carefully. These parameters have a major role in the estimation of the probabilistic seismic hazard analysis in the different regions. The city of Tehran which is the capital and the most populous city of Iran was chosen as our study area. The current research includes a history of more than 300 earthquakes in the past 117 years, which has been analyzed for Tehran and its suburbs with the aim of conducting a new FOSM (First Order Second Moment) algorithm. In this method, four ground motion relationships with the same weight were also used. Based on given design seismic levels and the Iranian Standard No.2800, the present study had the PGA in two levels. The first level which is, Design Basis Earthquake (DBE) defines the peak horizontal accelerations with 10% probability of exceedance in 50 years that was expected to occur once in approximately 475 years. The second is Maximum Considered Earthquake (MCE) that defines the peak horizontal accelerations with 2% probability of exceedance in 50 years which was expected to occur once in approximately 2,475 years. According to the FOSM algorithm, the estimated PGA for both levels was 0.30061 g and 0.55666 g, respectively.

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