Lab : 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. 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 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… -3:00 2:30:00

1,400km

The EQ happened somewhere on this line

Now work on the rest of the lab.