Aim: To interpret a seismograph, and locate the epicenter of an earthquake

Procedure A

1.  Using the three seismograms provide and the “Earthquake P-wave and S-wave Time Travel” graph in the Appendix, calculate the following for each city.

2.  Calculate the arrival times for P and S waves

3.  Calculate the difference in the arrive time between the P-waves and S-waves

4.  Calculate the distance (in km) to epicenter of each city

5.  Calculate the time at which the P-wave started (Origin Time)

Procedure B

1. Mark and label the epicenter on themap to set the drawing compass at the correct radius.

Questions and Answers

Report Sheet

Seismograph Station / “P” Wave / “S” Wave / Difference in time / Distance to epicenter / “P” Wave travel time / Time of Origin
Chicago / 2:33:00 / 2:35:30 / 0:02:30 / 1400 / 3min / 2:30:00
Tampa / 2:35:10 / 2:39:20 / 0:04:10 / 3000 / 0:05:40min / 2:29:30
Wink / 2:32:10 / 2:34:00 / 0:01:50 / 1000 / 0:02:20 / 2:29:50

1.  How do P-waves and S-waves differ?

P-waves arrive first and have the ability to travel through liquids while S-waves can not.

2.  What was the approximate location of the epicenter of this earthquake?

Some place between Wink and Tampa

3.  Why is three the minimum number of stations necessary to locate an epicenter?

So it minimums the percentage of error and makes it easier to locate

4.  Why does the time between the arrival of the P-waves and S-waves become greater and greater as you go farther away from the epicenter?

Because P-wave travel at a speed greater than S-waves, and after a while S-waves are bound to reach water which would stop the wave.