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 Topic: Seismic Wave Travel TimeTime

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Using the scaleUsing the scale x10x1033 km = 1000 km km = 1000 km

The The

EpicenterEpicenter

3000 km

3000 km

from

from

epicenterepicenter

1200 km

1200 km

from

from

epicenterepicenter

7000 km

7000 km

from

from

epicenterepicenter

4400 km

4400 km

from

from

epicenterepicenter

Time unit is minutesTime unit is minutes1 minute = 60 1 minute = 60

secondsseconds

0 0 secondsseconds

60 60 secondsseconds

20 20 secondsseconds

40 40 secondsseconds

8 min, 00 sec8 min, 00 sec

11 min, 40 sec11 min, 40 sec

3 min, 20 sec3 min, 20 sec

5 min, 30 5 min, 30 secsec

P waves

S waves

Epicenter

How long does it How long does it take for a P wave take for a P wave

to travel 4000 to travel 4000 km?km?

7 minutes7 minutes

How long does How long does it take for an S it take for an S wave to travel wave to travel

4000 km?4000 km?

12 min 40 sec12 min 40 sec

How far does an How far does an S wave travel in S wave travel in

21 minutes?21 minutes?

8200 km8200 km

How far does an How far does an P wave travel in P wave travel in

6 minutes 20 6 minutes 20 seconds?seconds?

3500 km3500 km

If the epicenter If the epicenter is 2000 km is 2000 km

away, and the P away, and the P wave is wave is

recorded at recorded at 5:04 am, what 5:04 am, what time did the time did the earthquake earthquake

occur?occur? 5:04 am – 4 min 5:04 am – 4 min = 5:00am= 5:00am

Final Question:Final Question:

• How much further does a P wave How much further does a P wave travel in 8 minutes than an S wave travel in 8 minutes than an S wave does?does?

P wave = 4800 P wave = 4800 kmkm

S wave = 2200 S wave = 2200 km km

Difference = Difference = 2600km2600km

Topic: How to Find The Topic: How to Find The Distance From an EpicenterDistance From an Epicenter

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2:30:00

2:36:00

The time different is 6 minutes

• We don’t know We don’t know when the when the earthquake started.earthquake started.

• We do know the We do know the difference between difference between the P&S wave the P&S wave arrival times.arrival times.

• 00:06:00 minutes00:06:00 minutes

• Find where Find where P&S are P&S are separated separated by 6:00 by 6:00 minutes.minutes.

• The distance The distance to the to the epicenter epicenter from the from the seismograph seismograph is 4400 km.is 4400 km.

Final Question:Final Question:• If a P wave arrives at 6:32 pm at the If a P wave arrives at 6:32 pm at the

seismograph, and the S wave arrives seismograph, and the S wave arrives at 6:34 pm, What is the distance to at 6:34 pm, What is the distance to the epicenter?the epicenter?

1400 km

P-wave AT = 6:32 AM

S-wave AT = 6:34 PM

Difference = 0:02 Min

Epicenter Distance = 1400 km