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EARTHQUAKE DEPTHS
Objective: To observe an earthquake’s focus.
You learned earlier in this chapter that Earth’s crust is broken into sections called plates.
Movement of these plates generates stress within rocks that must be released. When this
release of stress is sudden and rocks break, an earthquake begins.
Does the earthquakes focus depth affect the location of the epicenter?
Materials:
 Graph Paper
 Pencil
Quake
Focus Depth
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
-55 km
-295 km
-390 km
-60 km
-130 km
-195 km
-695 km
-20 km
-505 km
-520 km
-385 km
-45 km
-305 km
-480 km
-665 km
-85 km
-525 km
-85 km
-445 km
-635 km
-55 km
-70 km
Distance of Epicenter
from Coast (km)
0
100 east
455 east
75 east
255 east
65 east
400 east
40 west
695 east
390 east
335 east
95 east
495 east
285 east
545 east
90 west
205 east
25 west
595 east
665 east
95 west
100 west
Quake
Focus Depth
Distance of Epicenter
from Coast (km)
Procedures: (Read all procedures prior to starting the experiment)
1.
2.
Put the data table in order of distance from the coast, from west to east.
Create a line graph with the x-axis being the distance from the coast (km),
and the y-axis being the depth (km). (Remember that you are working with
negatives and therefore 0 km should be at the top of your graph).
Inference: (use complete sentences to answer the questions/10% off final grade if not
used)
1. Describe any observed relationship between the location of earthquake epicenters
and the depth of earthquake foci (plural for focus).
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2. Based on the graph you have completed, hypothesize what is happening at the
Earth’s surface in the vicinity of the plotted earthquake foci.
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3. In your opinion, what process is causing the earthquakes plotted on your graph?
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