What Are Logarithmic Scales?

In $1995$, an earthquake in Mexico registered $8.0$ on the Richter scale. In $2001$, an earthquake of magnitude $6.8$ shook Washington state. The formula $\log\frac{I_1}{I_2}=M_1-M_2$ compares the intensity levels of earthquakes where $I$ is the intensity level determined by the seismograph, and $M$ is the magnitude on a Richter scale. About how many times more intense was the $1995$ earthquake than the $2001$ earthquake?