The currently used magnitude scale for the energy released in an earthquake is officially named the moment magnitude scale, written MW. It is an exponential scale. An increase of one unit on the scale represents an increase in energy released by a factor of 32. An increase of two units represents an increase in energy release 1,000 times larger. This means that to dissipate the energy of one magnitude 7 earthquake, you would need to have 1,000 magnitude 5 earthquakes. An increase of 0.2 on the magnitude scale represents a doubling of energy released.
An earthquake with MW = 6.0 releases 6.3 x 1013 joules (63 terajoules) of energy, about the energy of a small atomic bomb. The largest earthquake measured so far, the Great Chilean earthquake of 1960, had MW = 9.5.
An older standard known as the Richter scale was also an exponential scale. Each increase of one unit on the Richter scale represented an order of magnitude (i.e., x10), increase in the amplitude of the motion of the ground. The moment magnitude scale has been adjusted to match the Richter scale for magnitudes under 8. For magnitudes above 8, the Richter scale becomes meaningless.