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Lab 4-5: Finding Epicenters. 2:33:00. 2:35:30. 2:35:30 – 2:33:00 =. 00:02:30. 2:35:10. 2:39:20. 2:39:20 – 2:35:10 =. 00:04:10. 2:32:10. 2:34:00. 2:34:00 – 2:32:10 =. 00:01:50. Let’s put the lab on pause for now…. How to use the P & S. Wave Chart. We don’t know when the EQ started.
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2:33:00 2:35:30 2:35:30 – 2:33:00 = 00:02:30
2:35:10 2:39:20 2:39:20 – 2:35:10 = 00:04:10
2:32:10 2:34:00 2:34:00 – 2:32:10 = 00:01:50
How to use the P & S Wave Chart
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!
We have to find a spot on the graph where P&S (careful!) are separated by 4:00.
Then drop straight down to see the distance to the epicenter. 2,600km
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
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
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
If the P-wave was detected at 2:33:00 and needed 3:00 minutes to travel it must have started at… 2:33:00 -3:00 2:30:00