What is the ratio of
- the intensities, and
- the amplitudes, of an earthquake P wave passing through the Earth and detected at two points 15 km and 45 km from the source?
In order to watch this solution you need to have a subscription.
This is Giancoli Answers with Mr. Dychko. Since the earthquake spreads out spherically from the epicenter that means these equations apply where you take intensity at position 2 divided by intensity at position 1, and it equals the distance from the epicenter to position 1 squared over the distance to position 2 squared. So, that's 15 kilometers squared divided by 45 kilometers squared. No need to convert this into meters since it's a ratio and the only thing that's important is that the units are the same, so they cancel. And we'll be left with 0.11. So, the intensity at position 2 is 11% of the intensity at position 1. As for the amplitudes, amplitude 2 over amplitude 1 equals r1 over r2. So, that's 15 over 45. So, amplitude 2 will be 33% of the amplitude at position 1.
Find us on:
