Before revision: 350px|Ground motion hazard map for Hawaii, based on a 2% probability of exceeding 0.2 second spectral acceleration at 5 Hz in 50 years 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 the approximate equivalent acceleration of a structure due to an excitation acceleration.
After revision: 350px|Ground motion hazard map for Hawaii, based on a 2% probability of exceeding 0.2 second spectral Acceleration at 5 Hz in 50 years Spectral acceleration (SA) is the approximate equivalent acceleration of a structure due to an excitation acceleration.