Henry Spall 1982 <p>Earthquakes can be measured in terms of either the amount of energy they release (magnitude) or the degree of ground shaking they cause at a particular locality (intensity). &nbsp;Although magnitude and intensity are basically different measures of an earthquake, they are frequently confused by the public and new reports of earthquakes. &nbsp;Part of the confusion probably arises from the general similarity of scales used express these quantities. &nbsp;The various magnitude scales represent logarithmic expressions of the energy released by an earthquake. &nbsp;Magnitude is calculated from the record made by an earthquake on a calibrated seismograph. &nbsp;There are no upper or lower limits to magnitude, although no measured earthquakes have exceeded magnitude 8.9.<br></p> application/pdf en U.S. Geological Survey Magnitude and intensity: Measures of earthquake size and severity article