Sunday, March 13, 2011

Earthquake Math

The most memorable earthquakes for me are the resent 8.9 magnitude in Japan (2001/03/11) and the 9.2 magnitude in the Indian Ocean (2004/12/26). Both of these earthquakes triggered a tsunami and caused immeasurable destruction.

But what do the numbers mean? How can we compare the magnitude of the two earthquakes?

The Richter magnitude scale assigns a number to quantify the amount of energy released by an earthquake. For example, an earthquake of magnitude 5.0 is 10 times stronger than an earthquake of 4.0. This is done using a base 10 logarithmic scale.

If we compare the two earthquakes from above, we see that one was 0.3 larger than the other. That means that it was 10 ^ 0.3 (10 to the power of 0.3) times stronger, which is very close to two times stronger.

Enroll yourself in Math B30 at to learn more about logarithms.

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