The Argonne National Laboratory Division of Educational Programs, hosts
"NEWTON," which is an "electronic community for Science, Math, and Computer
Science K-12 Educators." They have a brief, but nice, explanation of the
"For example, a magnitude 6 earthquake will produce ten times the ground
motion that a magntidue 5 earthquake will produce, but ten times less
ground motion than a magnitude 7 earthquake. The amount of energy released
by an earthquake varies by a factor of 30 for each unit increase in the
magnitude--a magnitude 6 earthquake produces 30 times the energy of a
magnitude 5 earthquake and 30 times less energy than a magnitude 7
earthquake. Incidentally, a magnitude 5 earthquake produces about as much
energy as the nuclear bombs dropped on Japan during World War II."
In your example, a magnitude 8 earthquake would produce 100 times (10 times
10) the ground motion of a magnitude 6 earthquake and 900 times (30 times
30) the amount of energy would be released by the magnitude 8 earthquake
than a magnitude 6 earthquake.
If you need any clarification, please feel free to ask.
Google search on: "Richter scale" earthquake
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