1. Lab : Finding Epicenters

2. 2:33:00
2:35:30
2:35:30 – 2:33:00 =
00:02:30

3. 2:35:10
2:39:20
2:39:20 – 2:35:10 =
00:04:10

4. 2:32:10
2:34:00
2:34:00 – 2:32:10 =
00:01:50

5. Let’s put the lab on pause for now…

6. How to use the P & S
Wave Chart

7. We don’t know when the EQ started.
But we know how much time there was between the P&S wave arrivals.
Let’s say 0:04:00
C’mon let’s say it!

8. We have to find a spot on the graph where P&S (careful
We have to find a spot on the graph where P&S (careful!) are separated by 4:00.

9. Then drop straight down to see the distance to the epicenter.
2,600km

10. Now that we know the EQ was 2,600km away, when did it start?
To travel 2,600km, a P-wave…
needs 5:00 minutes

11. Back to the lab…
The difference in arrival time for Chicago is 0:02:30.
That means that Chicago is ______ km from the epicenter.
1,400

12. Now that we know the EQ was 1,400km away, when did it start?
To travel 1,400km, a P-wave…
needs 3:00 minutes

13. If the P-wave was detected at 2:33:00 and needed 3:00 minutes to travel it must have started at…
-3:00
2:30:00

14. 1,400km

15. The EQ happened somewhere on this line

18. Now work on the rest of the lab.