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Rapid Earthquake Viewer (REV) Tutorial Worksheet
Answer Sheet
Name:
Directions:
Go to http://rev.seis.sc.edu/index.html
Work through this tutorial to learn about the capabilities of REV and complete the following
questions.
On the home page of the REV website are a list of the most recent earthquakes, a
highlighted “Earthquake in the News” and links to the Earthquake View, the
Station View, and a glossary.
1. Look in the “Earthquake in the News” box. List the three most recent earthquakes,
including the location, date, and magnitude.
Along the left side of the homepage you can find Recent Earthquakes. The top three
earthquakes will vary over time since earthquakes are added continuously.
A glossary provides definitions and supporting information about the earthquake
information provided by REV. Click on any bold and underlined word to access
the glossary.
2. Using the glossary, find the entry for seismogram and write a definition in your own
words.
Clicking on the underlined blue text takes you to the glossary definition for that word.
Scrolling allows you to access additional entries.
seismogram - A record written by a seismograph in response to ground motions produced by an
earthquake, explosion, or other ground-motion sources.
Navigate to Earthquake View.
On the Earthquake View page you see a map of the world centered over the Pacific
Ocean. Also on this page are separate links to different views of the world, and the
REV Help system. Below the map is a drop-down box with recent, notable
earthquakes listed.
3. What happens when you click on the Help button? Describe the areas outlined in the
Help section.
A short orientation to the Earthquake View page is provided here. The Earthquake View
Map area explains the map key and how to access additional information and switch views.
The Earthquake Box contains a list of recent earthquakes identified by the date they
occurred, the region in which they occurred, and the magnitude of the earthquake.
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When done, click on Help Off to return to the Earthquake View.
4. The map in Earthquake View has circles in three different colors. What does each of
these colors represent? The color indicates how long ago the earthquake occurred.



Red
Orange
Yellow
less than 3 days
less than one week
less than one year (though some significant older events are retained)
5. What do the sizes of the circles represent?
The size of the circle represents magnitude, smaller circles – smaller magnitude, larger
circles – larger magnitude
6. Using the drop-down box below the map, identify a large earthquake of 7.0 or greater
and note its location, date, and magnitude below.
Answers will vary.
For example, 2005-03-28 16:09GMT, Northern Sumatra, Indonesia, 8.7
Select this earthquake and click on the GO button to view more information about
the earthquake. Click on the Help button and orient yourself to the areas of this
page.
7. What are the three areas of the page identified in the Help section?
The Earthquake Info Box- This red box shows specific data about the earthquake you are
currently viewing.
The Record Section - This green box contains the record section, which shows the vertical
ground motion recorded at particular stations for your selected earthquake. These stations
are sorted by distance away from the earthquake epicenter.
The Station Info Box - This blue station info box contains the station code, name, and
distance (in degrees of arc and kilometers) from the earthquake epicenter for each station
seen in the record section.
When you are finished, click on Help Off.
8. On the Earthquake Information page, what does the circle on the map mean? What do
the triangles indicate?
The circle indicates the location of the epicenter. The triangles are the location of
seismograph stations where the earthquake was recorded. (Note that REV only displays a
small number of the hundreds of global seismic stations that might have recorded each
earthquake). These are also listed at the bottom of the page.
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9. Notice that the colored triangles on the map also appear at the top of the Seismograms
by Distance box. Describe the relationship between a triangle and the squiggly line below
it. Utilize Help and linked glossary terms if you need assistance with this.
The squiggly line below the colored triangle is the seismogram recorded at the station that
corresponds to the color as listed at the bottom. It represents the amount the ground shook
at that location over the course of time since the earthquake occurred at the epicenter.
Each station is ordered by increasing distance from the earthquake location. The
y-axis shows time since the earthquake in hours, minutes, and seconds
(HH:MM:SS). The scale reads from bottom to top.
10. How long after the earthquake occurred did the nearest station detect the ground
motion? The farthest station? One station near the middle? Describe the trend you notice.
Answers will vary for actual time of arrival. The farther the station is from the earthquake
epicenter (distance) the longer it takes for the ground motion to be detected (as expressed
by amplitude increasing when the seismic wave is detected).
Each station has a unique 3 to 6 letter code that identifies it. Station names can
often be long and this is a way for seismologists to quickly refer to or identify
stations. The two letters and/or numbers you will see at the start of the station
code in REV indicate the station's network code. For example, the code
"US.NHSC" refers to a station in New Hope, South Carolina in the United States
National Seismic Network.
11. Choose a station which is less than 100 degrees in distance from the earthquake and
click on the station code from the listing of stations at the bottom of the page to view
detailed information for this station.
RecordStation Code: Answers will vary depending on station selected
Station Name:
Distance to Earthquake (degrees and km):
Seismograms provide a visual and quantifiable representation of ground shaking
that occurs at a particular station. The amplitude of the seismic wave indicates
the amount of ground shaking that was recorded at that station over time. The
amplitude is measured from the center of the seismogram to the crest of the
wave.
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Be careful to read the plots properly. The y-axes for each of the three components are
often different from each other. This is done so that you can easily see the shape of the
waves. To pick the maximum amplitude, you need to read the largest amplitude off each
plot (taking into account the y-axis scale) and then select the largest value of those
three. Don't forget to check to see if the peak amplitude is on the negative side of the
axis – negative numbers just mean that the movement is in the opposite direction of the
positive numbers. It usually doesn't matter which is the maximum direction of the
shaking– only the amplitude of the movement.
12. What is the maximum amplitude recorded for this earthquake?
This is measured from the zero line of the y-axis up or down at the point of the largest
range of motion detected.
13. Why do you think the amplitude of the seismograms vary over time?
Amplitude changes (increases/decreases) when different types of seismic waves arrive at
the station, and dissipate over time, both resulting in a varied amplitude in the seismogram
over time. This question is meant to encourage the student to notice these changes at this
point, and speculate as to why the variation exists. This will be covered in more detail in
subsequent questions.
Select the “Overlay estimated P/S-wave arrival times” checkbox. Note: These flags are
estimated by a computer model; the model does not take into account slight variations
within the structure of the Earth and the difference in the materials through which the
waves are traveling. Hint: Click on the radio buttons under Select Zoom to magnify the
areas around the P or S wave.
14 a. What appears on each seismogram?
Red flags and markers appear overlaid on each seismogram near where amplitude begins
to increase.
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b. How long after the earthquake begins at the epicenter does the P wave arrive?
Remember time is recorded in HH:MM:SS on the seismogram graph.
Answers will vary. Time is read along the x-axis.
**c. Estimate the speed of P waves in kilometers per second. (Hint: speed = distance ÷
time. For the time, you'll need to convert from minutes into seconds). 1 km/second = 2237
miles per hour. How fast is this in miles per hour?
Answers will vary.
Example:
P arrives at 3 minutes, 3 seconds for station 1438 km away.
3 minutes = 3 * 60 seconds/minute = 180 seconds. 180 + 3 = 183 seconds
Speed = 1438 km ÷ 183 seconds = 7.86 km / second
7.86 km/s * 2237 mph / km/s = 17,583 mph
Note that this answer is not exactly correct because the distance between the earthquake
and the station is measured around the surface of the globe, but the P-waves are body
waves that travel through the globe. An accurate calculation would require you to know the
distance that the body waves actually traveled.
d. When does the S-wave arrive? Answers will vary. Time is read along the x-axis in
HH:MM:SS.
You can zoom in on the time period when the P and S waves arrived by selecting
Around P wave or Around S wave in the Select Zoom box. Try this and see if your
estimates of P and S wave arrival times change at all.
REV shows three seismograms for each station. They are labeled Vertical, NorthSouth, and East-West on the far right side of each seismogram. These record the
amount of motion in each direction separately. In an earthquake, the ground can
shake all over the place and in every direction. The seismogram labeled
"vertical" describes how much the station shook up and down. Where the line is
above 0, the station moved upwards. Negative values mean it dropped down.
Similarly, the seismograms for East-West and North-South indicate movement in
those directions. To visualize this, click here
http://www.teachingboxes.org/earthquakes/resources/3components.mov
In this animation, the first sequence shows just the North-South component of
shaking. Notice how the house only moves back in forth in a single direction. The
second shows only the East-West component. Again, it moves only in a single
direction along a straight line. The third part shows a more realistic scenario
with all three components of shaking at once. The purple square in this third
sequence stays stationary at the original location of the house. It's there to help
you recognize that the house is moving all over the place in every direction. The
seismometers in the three different directions record this motion, and you need
all three of them to reconstruct the motion completely.
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15. a. Look at the three seismograms. Are they the same? Pay attention to both the axes
and the shape of the wiggles. Describe the similarities and differences.
Y axis scales are usually different. The shape of the seismograms can look quite different.
**b. Which component records the highest amplitude during the time around the P wave
arrival? Which component records the highest amplitude around the S wave arrival? Are
they the same? If not, why do you think the amplitude would be different in different
directions for P waves and S waves? (Think about the direction of a fault slipping and how
the house moved in the animation.)
Answers will vary. The goal at this stage is for students to recognize that all three
components are needed to describe the motion of an earthquake.
c. Do you think it is important to record the amount of shaking in all different directions?
Why or why not?
Answers will vary. To calculate the full energy released by an earthquake, all directions
need to be recorded.
The figure below shows seismograms from three stations for the same earthquake shown on
the associated map. The amplitude scale for each of these is the same. The top seismogram
is from a station located approximately 55 degrees away (Charter Towers, Australia), the
middle one is 65 degrees away (Hobart, Tasmania), and the bottom one is 70 degrees away
(Magadan, Russia) from the earthquake epicenter. Note: This figure shows the seismograms
using the same unit of measure for all three, while the seismograms shown in the REV tool
are magnified so that more details are visible.
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16. What do you notice about these seismograms? What happens as the distance from the
station to the epicenter increases?
The arrival of the seismic wave occurs later and the amplitude of the seismogram is smaller
as distance from the epicenter increases.
Go Back (using your browser back button or clicking on “More about this earthquake in the
earthquake Info box) to the Earthquake View page. You can add more stations and
seismograms to the Seismograms by Distance from Earthquake box. Study the locations of
the seismograms and identify where there is a gap between them. Using the Add a station
dropdown box (left), select a station located in one of the gaps between
stations/seismograms.
17.
a. What station did you add?
b. What is its distance in degrees and km from the earthquake?
c. How does this added station's seismogram compare to the ones already on the
screen?
Click on Station View at the top of the page to explore another path through REV; the world
centered over the Pacific Ocean. Also on this page are separate links to different views of
the world, and REV’s Help system. Below the map is a text entry box for entering a zip code
to find the station nearest to that geographic area.
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18. Click on the Contiguous US map tab at the top of the page. Describe the pattern of
stations you see in the US. Why do you think this pattern exists?
Stations are clustered more densely in the western U.S.
The western United States is more seismically active and stations that are part of the
Global Seismic Network are concentrated in this area. An additional array of
transportable stations is being installed as well, beginning in the west and then moved
periodically to the east across the country.
Find and select the station closest to where you live by clicking a blue station icon or enter
your zip code in the text box near the bottom and click Go. On the left you can see the
location plotted on a map accompanied by place name and latitude and longitude.
19. RecordFor example:
Station name: Idaho Springs, Colorado, USA
Code: US.ISCO
Location: 39.80 N, 105.61 W
Today’s seismic record is displayed. Use the Previous Day and Next Day buttons to look at
the record over the last few days. Have any earthquakes been recorded? Check the box
beside Show Earthquakes (if any) to see if you are correct. If so, a box will appear on the
seismogram. Hover over it to identify any earthquakes and their point of origin.
20. Record any earthquakes that were detected at the station nearest you. Did you feel this
ground motion? If not, why?
Seismographs are sensitive enough to detect ground motion that humans cannot feel thus
not all earthquakes detected locally can be felt.
21. Did you see any seismic activity that was not related to an earthquake? What might
have caused it?
It is very likely that your seismometer is recording what seismologists call "noise." See
Teacher Background for more detail on this phenomenon.
22. You have now explored the main features of the Rapid Earthquake Viewer on-line data
access tool. How might you use this tool the next time an earthquake occurs?