Towards an Iranian national risk-targeted model for seismic hazard mapping

Abstract

Ideally, hazard assessment for seismic design should quantitatively control the risk of exceeding different limit states (LS) over the structure's lifetime. In fact, the geographical variation of the ground motion hazard curves has an impact on the total seismic risk of code-conforming buildings. This paper examines the path towards a ground motion intensity measure (IM) reflecting a consistent seismic risk using research results referring to Iran, which is one of the most seismically active regions on Earth and has a high level of vulnerability and loss. Recently, risk-targeted (RT) seismic hazard maps have been developed in regions such as the United States and Europe as a whole. This paper prepares a new seismic hazard map for peak ground acceleration (PGA) and spectral acceleration, Sa(T), at periods of 0.2 s and 1.0 s, at the national level, based on the most recent and well-founded hazard curves. Result stability (validation) is emphasized through an extensive analysis of the risk-targeting approach applied to Iran. Subsequently, as the performance of the buildings designed according to the Iranian national design code (Standard No. 2800), is currently unknown, the RT hazard adjustment for the previous hazard maps with the uniform return period (RP) are highlighted innovatively providing a basis for choosing appropriate seismic hazard levels within the country. Also, the results of this study recommend that the mapped design ground motions be changed even within the same seismic zones of Standard No. 2800. It is emphasized the necessity of the development of an updated and more accurate hazard model for Iran (the work is in progress). Finally, the presence of aleatory uncertainty in the risk-targeted IM (IMR) is first illustrated in this paper. Examples equip the study with how the quantified uncertainty may be relevant to geographic locations.