Fallahi - Assistant Professor, Dept. of Civil Engineering, Azarbaijan University of Tarbiat Moallem, Tabriz
Kitaura - Professor, Dept. of Civil Engineering, Kanazawa University, Kanazawa, ۹۲۰-۱۱۹۲, Japan
Miyajima - Professor, Dept. of Civil Engineering, Kanazawa University, Kanazawa, ۹۲۰-۱۱۹۲, Japan

According to aseismic codes, in determining design earthquake or establishing design spectrum it is necessary to use at least three acceleration time histories recorded at the site of construction. If it is not recorded any time history at the site, recorded time histories in other similar sites are selected. If it is difficult to find three recorded or to select such site-similar time histories, simulated time histories might be alternative. The aim of this study is to present a probabilistic method for simulating such (referred to as critical) earthquake for a given nonlinear structure which causes larger response on the structure but shows similar characteristics to a given record, referred to as target. The main idea in simulating critical earthquake is modifying the power spectral density (PSD) graph of target. The method is applied on a given nonlinear SDOF structure and it is clarified that a resulted critical earthquake satisfies restriction amplitude and frequency conditions.