The magnitude of an earthquake is the amount of energy released. Earthquakes vary enormously in magnitude. The magnitude of a quake is computed from measurements of the amplitude of ground vibrations. Energy released by an earthquake rises about 28 times for each unit. Our Geologic Environment.
Small earthquakes are very common.
Many occur each year due to the Earth's constant release of stress. The intensity of an earthquake is the damage caused by the seismic waves. The intensity is computed using the Mercalli Intensity Scale, which is a damage detector. An earthquake has a single magnitude but its intensity varies with distance. The maximum intensity occurs at the earthquake's epicenter, with intensities decreasing with distance.