Science Buddies: "Ask an Expert"

I'm doing a ScienceBuddies project that involves reading seismograms to find the epicenter of an earthquake. I can't really tell where the S-wave starts on the seismogram, though. Or, rather, I can't tell whether large jumps in the seismogram (there usually seem to be only one) are S-waves or surface waves, and my times seem to be getting mixed up and unproportional. Does anyone have advice for differentiating between them?

Hi kat09,

One option would be to do everything based on the P wave travel times. The first spike on the seismogram will be the P wave. This will be lower amplitude than the S wave, but it might be easier for you to identify.

Another option would be to try looking at the seismogram from another station, which might record the S wave more distinctly from the P wave. If the station you are looking at is quite close to the epicenter of the earthquake, then the P wave and S wave will arrive at the seismometer very close together. That would make it difficult to identify the S wave.

I would suggest going with the first option and using only the P wave arrival times. Let me know how that goes, and post back with any other questions you might have.