Applying the characteristic magnitude distribution Model for North Tabriz Fault (NTF) in Probabilistic Seismic Hazard Assessment (PSHA) and its effects on acceleration parameter and hazard curve

Iranian plateau is a part of Alpine-Himalayan active Mountain, which caused occurring major earthquakes across Iran. Hence, the estimation of seismic hazard parameters is required to design building and structures properly. Importance of acceleration parameter in the long-term return period, consequently affects the on site-specific design spectra for building standard law of countries (ASCE7-5, ASCE7-10, IBC, 038 code and Iranian Seismic Code 2800), so in seismic hazard analyses, selecting recurrence model is an important issue in hazard assessment. North Tabriz Fault (NTF) is one of the most seismotectonically active faults in Iran and it attracts the attention of numerous researchers because of obvious morphologic features and historical seismicity. Probability characteristic slip in intermediate of fault, documented by paleoseismic studies of Hessami et al. (2003), also the mathematical probability density function of the exponential model, are not suitable for sources of repeated large earthquakes. Exponential model is just able to estimate recurrence of small to moderate earthquakes, while recurrence of large magnitude earthquakes is much higher than the extrapolated exponential model. This difference lead to the development of the characteristic earthquake model (Schwartz and Coppersmith, (1984)). In this study, seismic hazard parameters around Tabriz city based on characteristic recurrence model has been investigated. First step in all hazard studies is determining the seismotectonic of the province. Based on this definition, Mirzaei et al. (1998) divided Iran in five major seismotectonic provinces. The covered area in this study is located in Alborz-Azerbaijan Seismic province. In order to have more information regarding the seismic hazard analysis, seismotectonic map of study area is prepared up to a radius distance of 150km from site. In this study both areal and linear seismic source model are considered. The reason for selecting areal seismic source model is due to the lack of enough information about dip and geometry of the fault. Recurrence models are defined for linear seismic sources, for those that there are enough data about them. In this study North Tabriz fault is considered as three separated segments, in which the characteristic recurrence model are used to define the intermediate segment of seismic source. Seismic hazard assessment requires the estimation of strong ground motion. The estimation of peak ground acceleration regard to recurrence model of source, magnitude, source-to-site distance, tectonic properties and source type using attenuation relationships that are the main part of seismic hazard assessment process. Estimation of peak ground motion acceleration in this study for horizontal component is based on the next generation of attenuation relationships for the west 2 project (NGA West 2).In this study, we used attenuation equation reported by Campbell-Bozorgnia (2014) NGA West 2, Kamai et al. (2014) NGA West 2, Idriss (2014) NGA West 2, Chiou-Youngs (2014) NGA West 2 and Boore et al. (2014) NGA West 2. The estimated results show that the segment which modeled by characteristic recurrence model in higher recurrence period, have higher value of acceleration.