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2.2 Reinforcing Key Concepts

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2.2 Reinforcing Key Concepts
SECTION
EARTHQUAKES RELEASE ENERGY.
2.2 Reinforcing Key Concepts
BIG IDEA Earthquakes
KEY CONCEPT
release stress that has built up in rocks.
Earthquakes release energy.
energy travels in all
directions—up and down and side to side. The energy travels as seismic waves. Earthquakes
produce three kinds of seismic waves—primary, secondary, and surface waves. Each type
moves through materials differently. The three diagrams below show the particle motion
resulting from each kind of wave. Label and briefly describe the wave shown in each
diagram. Also describe how the waves affect materials they pass through.
particle
motion
particle
motion
wave direction
wave direction
A.
particle
motion
wave direction
B.
2. Seismic waves can be measured. A
C.
seismograph is an instrument that constantly
records ground movements. Scientists at seismic stations all over the world know when
an earthquake occurs. Suppose that as an earthquake strikes, seismographs at two
stations record the movements of the ground. The seismic station at point A records P
waves at 10:52 A.M. and S waves at 11:09 A.M. The seismic station at point B records
P waves at 10:35 A.M. and S waves at 10:56 A.M. Which station is closer to the earthquake’s
epicenter? How do you know? How would scientists determine the exact location of the
earthquake’s epicenter?
Copyright © by McDougal Littell, a division of Houghton Mifflin Company
CHAPTER 2
Earthquakes
1. Energy from earthquakes travels through Earth. Earthquake
104 THE CHANGING EARTH, CHAPTER 2, REINFORCING KEY CONCEPTS
104-104-sean-urb-b0202-rkc 104
3/10/04, 4:29:17 PM
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