Transcript Unit III - mrsciguy

Lab 4-5: Finding Epicenters
2:33:00
2:35:30 – 2:33:00 =
2:35:30
00:02:30
2:35:10
2:39:20 – 2:35:10 =
2:39:20
00:04:10
2:32:10
2:34:00 – 2:32:10 =
2:34:00
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!) 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
1,400 km
Chicago is ______
from the epicenter.
• 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
1,400km
The EQ happened
somewhere on this line
• Now work on the rest of the lab.