Do Now
• Power on your laptops and download the
earthquake PS wave travel time notes.
• Please take out your reference tables.
• H.W. Continue your castle learning
assignment questions 31 – 36.
• Reminder:
– The 3rd quarter ends next Friday. All missing
work must be in by then or the ZERO stays!!
Topic: Seismic Wave Travel Time
YOUR BEST
FRIEND
Page 11
x103 km = 1000 km
Using the scale
7000 km from
epicenter
4400 km from
epicenter
3000 km from
epicenter
1200 km from
epicenter
The Epicenter
Time unit is minutes
1 minute = 60 seconds
60
40
20
0
seconds
seconds
seconds
seconds
11 min, 40 sec
8 min, 00 sec
5 min, 30 sec
3 min, 20 sec
S waves
P waves
Epicenter
How long does it
take for a P wave to
travel 4000 km?
7 minutes
How long does it
take for an S
wave to travel
4000 km?
12 min 40 sec
How far does an S
wave travel in 21
minutes?
8200 km
How far does an P
wave travel in 6
minutes 20
seconds?
3500 km
If the epicenter is
2000 km away,
and the P wave is
recorded at 5:04
am, what time did
the earthquake
occur?
5:04 am – 4 min =
5:00am
Final Question:
• How much further does a P wave travel in
8 minutes than an S wave does?
P wave = 4800 km
S wave = 2200 km
Difference =
2600km
Topic: How to Find The Distance
From an Epicenter
YOUR BEST
FRIEND
Page 11
2:36:00
2:30:00
The time different is 6 minutes
• We don’t know when
the earthquake
started.
• We do know the
difference between
the P&S wave arrival
times.
• 00:06:00 minutes
• Find where
P&S are
separated
by 6:00
minutes.
• The distance
to the
epicenter
from the
seismograph
is 4400 km.
Final Question:
• If a P wave arrives at 6:32 pm at the
seismograph, and the S wave arrives at
6:34 pm, What is the distance to the
epicenter?
P-wave AT = 6:32 AM
S-wave AT = 6:34 PM
Difference = 0:02 Min
Epicenter Distance =
1400 km
1400 km