“Locating the Epicenter of an Earthquake”
In order to practice triangulation we will use data from three separate earthquakes and locate three epicenters.
Table 1 shows the distance of three separate earthquakes from each of the recording stations provided on the
data map. Each earthquake is labeled by the date on which it occurred (October 9, October 16, and March 17).
Section I : (In complete sentences!)
1. In your own words, describe what is meant
by the process of “triangulation.”
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2. What is the difference between the “focus”
of an earthquake and the “epicenter” of an
earthquake?
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3. What is the “radius” of a circle?
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4. Draw and label a the radius on the circle to
the right:
Procedure:
1. Start by locating the epicenter for the October
9th Earthquake.
2. Notice that the map key shows us that 1 cm =
1 mile (mi.)
3. Using your ESRT ruler set your compass to
the width of 7.5mi to represent the distance
Van Nuys is the to epicenter.
4. Place the center of your drawing compass on
the point of the map that says Van Nuys.
5. Draw the circle (epicenter distance)
accordingly.
6. Repeat this procedure for the two remaining
recording station measurements.
7. Locate the city nearest the epicenter. (Recall
that the epicenter is located where the three
circles intersect!)
8. Repeat steps 1-9 for the data from the other 2
earthquakes (October 16th, & March 17th)
DATA TABLE 1:
*
5. What is the radius of this circle in
centimeters? (Round to the nearest tenth)
__________ cm
6. If the center of the circle was a seismic
station and 1cm = 1mi what would be the
distance this seismic station is from the
epicenter? ____________mi
7. When the three circles are drawn, what
occurs at the location where they all
intersect?
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(Hint: This Table is also found on your Map Worksheet)
Recording
Station
Van Nuys
Westwood
Simi
Valley
City Nearest to
Epicenter
October
9th
Quake
October
16th
Quake
March
17th
Quake
7.5 mi
8.5 mi
8.5 mi
4.0 mi
4.5 mi
8.0 mi
4.0 mi
8.0 mi
11.0 mi
Section III: Analysis and Conclusion
1. Which station was closest to the epicenter of the March 17th Earthquake?___________
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2. Which city probably felt October 16th Earthquake last? Why did you choose this answer?
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3. Which earthquake occurred directly along a fault line?_________________________
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4. Why must we use data from at least three recording stations to locate an epicenter? ___
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5. Thinking: Besides proximity (how close something is) to an epicenter, what other factors
might contribute to the amount of destruction at a certain location? Give at least 2
examples. __________________________________________________________
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October 9th Quake
Section II:
2. Explain why S-waves from this earthquake were
not directly received on the opposite side of Earth.
1. Which part of this seismogram is used to find the
distance to the epicenter of the earthquake?
(1) P-wave arrival time, only
(2) S-wave arrival time, only
(3) difference in the arrival time of the Pwave and S-wave
(4) difference in the height of the P-wave
and S-wave
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3. The first S-wave arrived at a seismograph station
11 minutes after an earthquake occurred. How long
after the arrival of the first P-wave did this first Swave arrive?
(1) 3 min 15 s (3) 6 min 05 s
(2) 4 min 55 s (4) 9 min 00 s
October 16th Quake
Section III:
1. In the United States, most of the major damage
expected from a future earthquake is predicted to
occur near a
(1) divergent plate boundary, only
(2) convergent plate boundary, only
(3) mid-ocean ridge and a divergent plate boundary
(4) transform plate boundary and a hot spot
2. Which New York State location has the greatest
risk of earthquake damage?
(1) Binghamton
(2) Plattsburgh
(3) Buffalo
(4) Elmira