An earthquake measuring 64 on the Richter scale struck Japan

An earthquake measuring 6.4 on the Richter scale struck Japan in July 2007, causing extensive damage. Earlier that year, a minor earthquake measuring 3.1 on the Richter scale was felt in parts of Pennsylvania. How many times more intense was the Japanese earthquake than the Pennsylvania earthquake? (Round your answer to the nearest whole number.) times

Solution

M = log(I/S)

where S is the intensity of std eartquake.

6.4 = log(I1/S)

3.1 = log(I2/S)

subtracting 2nd from 1st:

6.4 -3.1 = log(I1/S) - log(I2/S)

3.3 = log(I1/I2)

I1/I2 = 10^3.3

I1 = 1995I2

So, eartquake in Japan was 1995 times stronger than eqrtquake in Pennsylvania