Name: _______________________________
Date:_________________
Period:_______________
Earth Science Regents
Earthquake Epicenter Lab #________
Purpose: The goal of this lab is to learn how recording of earthquakes — seismograms are used
to locate earthquakes. The P-waves arrive first and are later swamped by the arrival of the Swaves, The S - P interval is the time between the first arrivals of the P and S waves; it is used
to determine the distance from the epicenter.
Problem:_________________________________________________________________
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Hypothesis:______________________________________________________________
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Vocabulary:
P-waves - ________________________________________________________________
S-waves - ________________________________________________________________
Seismogram - _____________________________________________________________
Seismic Waves - ___________________________________________________________
Epicenter - ______________________________________________________________
Focus - _________________________________________________________________
Lithosphere - _____________________________________________________________
Mantle - _________________________________________________________________
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Procedures:
1. Measure the S-P interval from the 3 seismograms shown on the following page, and
enter the results in Table #1. Then, use the S-P travel time curve (from your E.S.R.T.) to
determine the distance between the station and the epicenter and enter the data into the
table.
2. Next, take a safety compass and set its radius to the epicentral distance for each station
and draw circles around each station. Ideally, the three circles should intersect at a single
point, which is the epicenter — if they do not, you should go back and check your work.
3. Place an X on the map which identifies the epicenter of this earthquake.
Table #1
Station
Difference between P- and SWave Arrival Times
Distance to Epicenter
Eureka, CA
Elko, NV
Las Vegas, NV
2
3
4
Questions:
1.
Is there a known fault in the vicinity of the epicenter from the laboratory activity that
is likely to have slipped to create the earthquake? If so, name the fault.
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Base your answers to questions 2 through 6 on the map below, which shows seismic stations
X, Y, and Z that have recorded seismic waves from the same earthquake. The distances from
seismic stations X and Y to the earthquake epicenter have been drawn on the map. Locations
A, B, C, and D represent possible earthquake epicenters. The distance from seismic station Z
to the earthquake epicenter has been deliberately omitted.
2. How far is station X from the earthquake epicenter? ___________________________
3. How long did the P-wave take to travel from the earthquake epicenter to station Y?
______________________________
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4. Compare the speed of S-waves in a given Earth material, to the speed of P-waves.
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5. Station Z recorded a time difference of 6 minutes 40 seconds between the arrival of the
P-waves and the arrival of the S-waves. The earthquake epicenter was located closest to
which location?
______________________________
6. If the earthquake's focus was 2 kilometers below Earth's surface, the earthquake
occurred in which layer of the Earth’s Interior?
_______________________________
7. A student read an article in the local newspaper stating that a major earthquake can be
expected to affect the region where the student lives within the next year. The student's
family plans to stay in this region. As a result, the student decides to help prepare her home
and family for this expected earthquake.
State three specific actions the student could take to increase safety or reduce injury or
damage from an earthquake.
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6
Base your answers to questions 8 through 11 on the map and seismograms below. The map shows
seismic stations in Chicago, Denver, Oklahoma City, and Tampa that recorded data from an
earthquake. Seismograms A, B, C, and D show, in Greenwich time, the arrival times of the
earthquake waves at the four stations.
8. The P-wave generated by this earthquake took 2 minutes and 40 seconds to reach one of
the seismic stations. Approximately how long did the S-wave take to reach this same seismic
station?
______________________________________
9. Which seismogram was recorded at Tampa? __________________________________
10. What is the minimum number of seismic stations needed to locate most earthquake
epicenters?
_______________________________________
11. What was the origin time of this earthquake?________________________________
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Conclusion:
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