Earthquake wave attenuation depends upon the wave type. They are also attenuated by heating. Some propagate along the surface and some do not go through water. The intensity does not in general follow an inverse square law reduction in intensity.
This is an ill-advised question, but they probably want you to assume that intensity varies with the inverse square of distance. To do that, multiply
5*10^6 W/m^2 by (55/3)^2
The intensity of a particular earthquake wave is measured to be 5.0 multiplied by 106 J/m2·s at a distance of 55 km from the source.
(a) What was the intensity when it passed a point only 3.0 km from the source?
(b) What was the rate energy passed through an area of 7.0 m2 at 3.0 km?
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