In this activity, you will be going to the "Virtual Earthquake" website where you will be doing a series of guided tasks related to locating the epicenter and determining the magnitude of an earthquake.  Print out or otherwise have these activity questions available to you before you click on the link below.URL:  http://www.sciencecourseware.com/VirtualEarthquake/VQuakeExecute.html

Choose the region “San Francisco area” for your simulation of an earthquake and click “submit choice”. 

What does the S-P interval represent exactly?  Choose the best answer below:

Select one:a. It means you can measure the distance the waves have traveled.

b. It is the time interval between the arrival of the P-wave and the arrival of the S-wave at a seismic station.

c. It is the distance between the earthquake epicenter and the seismic station.

d. It represents the earthquake itself.

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Click on “View Seismograms” at the bottom of the page.  Choose the closest number that represents the S-P interval you got for each station (Questions 4, 5 & 6) below:

Question 4

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Eureka, CA:

Select one:a. 49 seconds

b. 28 seconds

c. 17 seconds

d. 98 seconds

e. 240 seconds

Question 5

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Elko, NV:

Select one:a. 22 seconds

b. 55 seconds

c. 72 seconds

d. 102 seconds

e. 538 seconds

Question 6

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Las Vegas, NV:

Select one:a. 54 seconds

b. 40 seconds

c. 64 seconds

d. 84 seconds

e. 162 seconds

Question 7

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Click on “Convert S-P Interval”.  Read the information on “Determining the Earthquake Distance”. 

It takes an S-wave approximately 70 seconds to travel 300 km.  How long does it take the P-wave to travel this same distance?  Choose the best answer below

Select one:a. 70 seconds

b. 540 km

c. 39 km/s

d. 39 seconds

e. 520 km

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Use the S-P graph at the bottom of the webpage and the estimates you made for the S-P travel times for the three seismograms.  Choose the closest number that represents the closest distance in the space below:

Question 8

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Eureka, CA:

Select one:a. 501 km

b. 302 km

c. 478 km

d. 355 km

e. 203 km

Question 9

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Elko, NV:

Select one:a. 740 km

b. 504 km

c. 579 km

d. 703 km

e. 520 km

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Las Vegas, NV:

Select one:a. 602 km

b. 402 km

c. 623 km

d. 690 km

e. 562 km

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Type in your answers above into the boxes provided on the webpage and hit “Find Epicenter”.  The next screen will be a map showing circles.  What are these circles themselves individually depicting?

Select one:a. The region that experienced earthquake shaking.

b. The distance the S and P waves traveled.

c. The distance between the seismic recording station and the possible earthquake epicenter.

d. The region that received damage during the earthquake.

Question 12

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Richter Magnitude

Read the section on “Magnitude Explained”.  What is the magnitude of an earthquake?  Choose the best answer from the choices below

Select one:a. It is a measurement of how big an earthquake is.

b. It is a scale in which earthquakes are rated depending on how strong they are.

c. It is an estimate of the total amount of energy released by an earthquake.

d. It is a measurement of how strong an earthquake is based on the damage created.

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The Richter magnitude determination is based on measurements made on seismograms.  Two measurements are needed.  What are they?

Select one:a. Maximum amplitude of the seismic waves and the S-P time interval.

b. Maximum amplitude of the seismic waves and distance the seismic waves travel.

c. Magnitude of the earthquake and distance the seismic waves travel.

d. S-P interval and the distance the seismic waves travel.

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Click on “Go to next page”.  Read the information on the “Richter Nomogram” and then click on “Go to next page” again.  Measure the maximum amplitude of the S-wave for each seismogram and record your estimate in the box below the seismogram, then select the best answers from the choices (Questions 14, 15 & 16) below:

Question 14

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Eureka, CA:

Select one:a. 250 mm

b. 50 mm

c. 285 mm

d. 490 mm

e. 300 mm

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Elko, NV:

Select one:a. 50 mm

b. 120 mm

c. 40 mm

d. 510 mm

e. 60 mm

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Las Vegas, NV:

Select one:a. 400 mm

b. 200 mm

c. 64 mm

d. 30 mm

e. 100 mm

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The page shows a nomogram with three lines representing the data you provided.  Type in your estimate for the earthquake in the box provided on the webpage and click on “Confirm Magnitude”.  Choose the magnitude below that most closely represents the magnitude for this earthquake.

Select one:a. 7.5

b. 7.1

c. 7.8

d. 6.5

e. 6.1

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