To learn if earthquakes occur in the El Paso area, CLICK HERE.
OBJECTIVE: Using the information from three seismology observation stations, you will locate the epicenter of an earthquake.
MATERIALS NEEDED: an outline map showing all the continental United States, a compass for drawing circles, and a calculator if permitted by teacher. You may wish to print this page for referrence. If you need an outline map, CLICK HERE for a map you can print out for the exercise.
PROBLEM: An earthquake has occurred somewhere in the United States. Using the information in the table below, calculate the S - P times in seconds. Then using that information and the formula
Example: S = 24 seconds and P = 12 seconds, then S - P would equal 12 seconds. Placing that information into the formula D = 12km/sec(12 sec) = 144 km. Now, using a compass and the kilometer scale at the bottom of the map, draw a circle around that city equal to 144 km.
After you have calculated the distance and drawn the circles for each of the three cities you should have one spot on the map where all three circles intersect. This point of intersection is the epicenter of the earthquake.
| CITY | P WAVE TIME | S WAVE TIME |
| El Paso, TX | 10:20:20 MDT | 10:20:47 MDT |
| San Francisco, CA | 9:23:27 PDT | 9:25:27 PDT |
| Seattle, WA | 9:25:09 PDT | 9:27:53 PDT |