SEISMIC%20WAVE%20BASICS

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SEISMIC WAVE BASICS
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Finding an Epicenter
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What is an Epicenter?

• A point on the surface of the Earth directly
  above the FOCUS of the earthquake.

• The point within the Earth from which earthquake
  waves originate.

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(No Transcript)
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Use the data from the recording stations

• Station A San Francisco, California
• P-Wave arrival 30220 S-Wave arrival 30630

What is the time difference between P and S wave
arrivals?
410
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Use the data from the recording stations

• Station B Denver, Colorado
• P-Wave arrival 30140 S-Wave arrival 30500

What is the time difference between P and S wave
arrivals?
320
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Use the data from the recording stations

• Station C Missoula, Montana
• P-Wave arrival 30100 S-Wave arrival 30300

What is the time difference between P and S wave
arrivals?
200
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Difference in arrival times
San Francisco 410
Denver, Colorado 320
Missoula, Montana 200
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TAKE A PIECE OF PAPER, AND MARK OFF THE
DIFFERENCE IN ARRIVAL TIME
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MOVE THE PAPER UNTIL THE TWO TICK MARKS LINE UP
WITH THE P AND S CURVES
WHEN TICK MARKS LINE UP, GO STRAIGHT DOWN AND
READ THE EPICENTER DISTANCE
EPICENTER DISTANCE OF 2800 KM
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EPICENTER DISTANCES
San Francisco 410
2,800km
Denver, Colorado 320
2,000km
Missoula, Montana 200
1100km
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Recording BoardDifference in arrival times
San Francisco 410
2,800km
Open your compass to the EXACT distance on the
scale.
3,000
4,000
5,000
1,000
2,000
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Use your carefully set compass to draw a circle
around each city.
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.
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You've found the epicenter!