To find the epicenter of an earthquake, seismologists use data from three recording stations to triangulate the location. The time difference between when the P and S waves arrived is used to calculate the distance from the epicenter. Circles are drawn around each station at the calculated distances, and where the circles intersect is the epicenter. Practice using recording station data, a map, compass, and calculations to locate an earthquake's epicenter.

1. Finding an Epicenter -DeMarco

2. What is an Epicenter? A point on the surface of the Earth directly above the FOCUS of the earthquake. The point within the Earth from which earthquake waves originate.

3. How can I find out where an earthquake happened? You will need data from 3(three) recording stations. You will need your ESRT You will need scrap paper You will need a map of the area You will need a map scale You will need a drawing compass

4. Use the data from the recording stations: Station A: San Francisco, California P-Wave arrival 11:26:10 S-Wave arrival 11:28:50 What is the time difference between P and S wave arrivals? 2:40

5. Recording Board Difference in arrival times: San Francisco: 2:40

6. Use the data from the recording stations: Station B: Denver, Colorado P-Wave arrival 11:28:50 S-Wave arrival 11:33:50 What is the time difference between P and S wave arrivals? 5:00

7. Recording Board Difference in arrival times: San Francisco: 2:40 Denver, Colorado: 5:00

8. Use the data from the recording stations: Station C: Seattle, Washington P-Wave arrival 11:26:20 S-Wave arrival 11:31:50 What is the time difference between P and S wave arrivals? 5:30

9. Recording Board Difference in arrival times: San Francisco: 2:40 Denver, Colorado: 5:00 Seattle, Washington: 5:30

10. Recording Board Difference in arrival times: San Francisco: 2:40 Denver, Colorado: 5:00 Seattle, Washington 5:30 Using your ESRT, find out how far away (in Km) each of the locations must be from the epicenter. (Use the scrap paper tick mark method!) =1,600km =4,000km =3,400km

11. Recording Board Difference in arrival times: San Francisco: 2:40 =1,600km 1,000 2,000 3,000 4,000 5,000 Open your compass to the EXACT distance on the scale.

12. Use your carefully set compass to draw a circle around each city.

13. All three circles should intersect at one point You've found the epicenter!