[[wiki-architecture]] · [[Buildings and Structures]] · [[ARCHITECTURE]] · [[000]] # Spectral acceleration 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. 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, although there is normally a correlation between [short period] SA and PGA. Some seismic hazard maps are also produced using spectral acceleration. == See also == Seismic scale == External links == Spectral Acceleration Hazard Map of California – for 1 sec period Archived 2015-05-11 at the Wayback Machine 2005 National Building Code of Canada – Spectral Acceleration Hazard Maps for various periods Revision of Time-Independent Probabilistic Seismic Hazard Maps for Alaska What is a ground shaking hazard map? – Includes explanations of SA and PGA == References ==