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Spectral acceleration (SA) is a unit measured in ''g'' (the acceleration due to Earth's gravity, equivalent to g-force) that describes the maximum acceleration in an earthquake on an object – specifically a damped, harmonic oscillator moving in one physical dimension. This can be measured at (or specified for) different oscillation frequencies and with different degrees of damping, although 5% damping is commonly applied.〔(Intensity Measure Type (IMT) ) OpenSHA, accessed 2011-04-14〕 The SA at different frequencies may be plotted to form a response spectrum. Spectral acceleration, with a value related to the natural frequency of vibration of the building, is used in earthquake engineering and gives a closer approximation to the motion of a building or other structure in an earthquake than the peak ground acceleration value,〔(FAQs - What is "spectral acceleration" or SA? ) United States Geological Survey, accessed 2011-04-14〕〔 although there is normally a correlation between (period ) SA and PGA.〔 Some seismic hazard maps are also produced using spectral acceleration. ==See also== *Peak ground acceleration *Seismic scale 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「spectral acceleration」の詳細全文を読む スポンサード リンク
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