Locating the Epicenter of an Earthquake:Travel Time

[ZDude43]

I am terrified. My science experiment results are due Tuesday and I don't understand the travel time graph. How does the curve work? What is the rise/run for it? I honestly can't make heads or tails of it please help.

[donnahardy2]

Hi,

Please relax; you are going to do a really good job on your science project. Please read the following explanation and I think it will help you understand how to use the time travel graph for your project.

I think you are doing this great, but challenging project from the Science Buddies website:

https://www.sciencebuddies.org/science- ... p018.shtml

In this project, you use archived data from 3 different stations on the USGS website to locate the epicenter of an earthquake.

Have you selected an earthquake to study and do you have the seismograms available that you can identify the precise times that the P and S waves started? The difference in seconds between and P and S waves can be used to determine how far a seismograph station was located from the epicenter. You will need to calculate Ts minus Tp for 3 seismograph stations to determine the epicenter. With this information, you can use the time/travel graph to find out the distance from the epicenter. In the example given for the Parkfield earthquake, The Ts-Tp is 17.6 seconds, which corresponds to a 140 Km distance from the epicenter. Look at the graph and confirm that you see where this value comes from. If the Ts minus the Tp is 40 seconds then the station is 400 Km from the epicenter; if it's less than a second, then the station is on the epicenter. Does this make sense now? You are looking for the difference in seconds between the P and S lines on the time travel graph.

Let me know if you have more questions.

Donna Hardy

[ZDude43]

So lets say if the difference between the times was 21.8 seconds, would that correspond to 190 kilometers?

[donnahardy2]

Hi

Yes, you are correct! I think you've got it now. You can analyze your results now. Any more questions?

If you have any questions about completing your report/project board, you can refer to the "analyzing your data and drawing a conclusion," and "communicating your results," sections on the Science Buddies website. Also, check your teacher's written assignment to make sure you include all the required details.

Also, tomorrow after you have turned in your project, please go the Science Buddies home page, and select the blue “My Science Buddies" tab on the top menu bar. Next select, "I did this project!" and give us your feedback. Your suggestions on what we could do to help students in the future to understand the time/travel graph would really help us a lot.

Good luck!


Donna Hardy