Name ___________________________
Chapter 8
Class ___________________
Earthquakes and Earth’s Interior
Date _____________
Exploration Lab
Locating an Earthquake
The focus of an earthquake is the actual place
within Earth where the earthquake originates.
When locating an earthquake on a map, scientists
plot the epicenter, the point on Earth’s surface
directly above the focus. To locate an epicenter,
records from three different seismographs
are needed.
New York, NY
9:00 UTC (Time marks in minutes)
Problem How can you determine the
location of an earthquake’s epicenter?
Seattle, WA
Materials
• drawing compass
• world map or atlas
Skills Measuring, Interpreting Maps,
Interpreting Graphs
9:00 UTC
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Procedure
1. The seismograms shown in Figure 1
Mexico City, Mexico
recorded the same earthquake. Use
the Travel-Time Graph to determine the
distance of each station from the epicenter.
Record your answers in the Data Table.
2. Refer to a world map or atlas for the
locations of the three seismic stations. Place
9:00 UTC
a small dot showing the location of each of
Figure 1
the three stations on the map in Figure 2.
Neatly label each city on the map.
3. On the map in Figure 2, use a drawing compass to draw a circle
around each of the three stations. The radius of the circle, in miles,
should be equal to each station’s distance from the epicenter. Use
the scale on the map to set the distance on the drawing compass for
each station. CAUTION: Use care when handling the drawing compass.
DATA TABLE
New York
Seattle
Mexico City
Elapsed time between first P and first S waves
Distance from epicenter in miles
NYC:
40° 45' 22",
-73° 59' 13"
Seattle:
47° 37' 16",
-122° 20' 50"
Mexico City:
19° 25' 38",
-99° 7' 39"
Earth Science
183 MX Cty: 19 N, 99 W
NYC: 41 N, 74 W, Seattle:
48Lab
N,Manual
122 W,
■
Name ___________________________
Class ___________________
Analyze and Conclude
1. Using Graphs How far from the
epicenter are the three cities located?
1000
17
Date _____________
Distance in kilometers
2000
3000
4000
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15
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13
S-wave curve
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2. Calculating What would the
distances from the epicenter to the
cities be in kilometers?
Time in minutes
11
10
9
8
7
6
P-wave curve
5
4
3. Interpreting Maps What is the
approximate latitude and longitude
of the epicenter of the earthquake
that was recorded by the three
stations? Use the map in Figure 3.
3
2
1
0
500
1000 1500 2000
Distance in miles
2500
3000
4. Drawing Conclusions On the New
Figure 2 Travel-Time Graph
York seismogram, the first P wave
was recorded at 9:01 UTC. UTC is
the international standard on which most countries base their time.
At what time (UTC) did the earthquake actually occur? Explain.
70
60
60
50
50
40
40
30
30
10
10
20
20
0
0
170
180
170
160
150
0
Figure 3
140
1000
130
120
2000
110
100
3000
90
4000
80
5000
70
60
50
40
30
6000
Scale of miles
Earth Science
184 MX Cty: 19 N, 99 W
NYC: 41 N, 74 W, Seattle:
48Lab
N,Manual
122 W,
■
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
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