In 1989, an earthquake with a magnitude of 6.9 on the Richter scale hit Northern California. In 2008 an earthquake with a magnitude of 5.4 hit Southern California. How many times more intense was the earthquake in 1989 than the one in 2008.

The Richter Scale calculates earthquake intensity on a logarithmic scale.

So, a magnitude 6 earthquake has 10 times the energy of a magnitude 5 earthquake.

The difference between 6.9 and 5.4 is 1.5 and so the difference in intensity is 10^1.5 or about 31.62.