Answer
Total area effected by the earthquake: 2,543,400 km$^{2}$
Work Step by Step
We will treat the distance that the earthquake was felt as the radius since it was in all directions.
Area of a Circle: $A$ = $\pi$$r$$^{2}$
Therefore:
$A$ = (3.14)(900 km)$^{2}$
$A$ = 2,543,400 km$^{2}$
