The intensity of an earthquake wave passing through the Earth is measured to be $3.0 \times 10^6 \textrm{ J/m}^2\cdot\textrm{s}$ at a distance of 54 km from the source.

VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. The intensity at position 1 divided by intensity a position 2 is the distance to position 2 squared divided by distance position 1 squared. And we can multiply both sides by i2 and the intensity of the earthquake at 1 kilometers away is going to be intensity at 54 kilometers multiplied by 54 kilometers squared divided by 1 kilometer squared. And the kilometers don't need to be converted to meters because they're going to cancel anyway and the only important thing is that their units are the same, although you couldn't turn them into meters, that would be fine too. So, we get 8.7 times 10 to the 9 watts per square meter is the intensity at 1 kilometer from the earthquake. And then the rate of energy transfer through the area, rate of energy transfer is its power, joules per second. And so intensity is power per area. And we can multiply both sides by area and get power is intensity times area. So, that's 8.748 times 10 to the 9 watts per meter squared intensity at 1 kilometer from the earthquake times 2 meter squared. And that gives 1.7 times 10 to the 10 watts but I wrote it as joules per second just to make it clear that this is energy rate of energy transfer, joules per second.