Answer
2512 times more intense
Work Step by Step
Given the magnitude equation $M = \log \frac{I}{S}$
with $S = 10^{-4}$
The question asks for how much more intense the San Francisco earthquake (M= 8.3) was compared to the Japan earthquake (M = 4.9) in 1906.
S is a constant that is already factored into the Magnitudes, so the $10^{-4}$ isn't necessary
$(8.3 - 4.9) = \log I$
$10^{3.4} = {I}$
$I = 2512$ times more intense
