Peak ground acceleration
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Peak ground acceleration (PGA) is a measure of earthquake acceleration. Unlike the Richter magnitude scale, it is not a measure of the total size of the earthquake, but rather how hard the earth shakes in a given geographic area.
Unlike the Mercalli intensity scale, it is measured by instruments, not from personal reports, although it generally correlates well with the Mercalli scale.
Peak ground acceleration can be measured in g (the acceleration due to gravity) or m/s².
The peak horizontal acceleration (PHA) is the most commonly used type of ground acceleration in engineering applications.
Other ground motion parameters used to characterize earthquake motion include peak velocity and peak displacement.
