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Published byKeon Harrow Modified about 1 year ago

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Finding an Epicenter Finding the Distance to the Epicenter of an Earthquake!

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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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Use the data from the recording stations: Station A: San Francisco, California P-Wave arrival 3:02:20S-Wave arrival 3:06:30 What is the time difference between P and S wave arrivals?

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Use the data from the recording stations: Station B: Denver, Colorado P-Wave arrival 3:01:40S-Wave arrival 3:05:00 What is the time difference between P and S wave arrivals?

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Use the data from the recording stations: Station C: Missoula, Montana P-Wave arrival 3:01:00S-Wave arrival 3:03:00 What is the time difference between P and S wave arrivals?

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Difference in arrival times: San Francisco: 4:10 Denver, Colorado: 3:20 Missoula, Montana: 2:00

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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: 4:10 Denver, Colorado: 3:20 Missoula, Montana 2:00 2,800km 1100km 2,000km

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Recording Board Difference in arrival times: San Francisco: 4:10 2,800km 1,000 2,000 3,000 4,0005,000 Open your compass to the EXACT distance on the scale.

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Finding the Earthquake Origin Time You take a distance to epicenter that you have already determined, or one given to you Let’s say the epicenter distance is 4400km, and the arrival time is 3:21:15 PM Well, use your ESRT and do some time math!!! Let’s try it

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Do it! Find the distance on the horizontal axis. Go up to the point where you hit the P- wave travel line. Go over to the vertical axis and read off the travel time for the P- wave. P wave travel time = 00:07:40 Epicenter dis = 4400km

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Now, do the math! Take the arrival time, and subtract the travel time from it! 3:21:15 – 00:07:40 = 3:13:35 So, the origin time of the Earthquake is 3:13:35 PM. Now YOU try it for San Francisco!!

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