1. Earthquakes 7.1 Earthquakes occur along faults. 7.2
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Earthquakes
the BIG idea
Earthquakes release stress that has built up in rocks.
7.1
Earthquakes occur along faults.
7.2
Earthquakes release energy.
7.3
Earthquake damage can be reduced.
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2. Earthquakes occur along faults.
7.1
Earthquakes occur along faults.
Normal faults form as rocks are pulled apart.
fault
stress
earthquake
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3. Earthquakes occur along faults.
7.1
Earthquakes occur along faults.
Normal faults form as rocks are pulled apart.
Reverse faults form as rocks are pushed together like the Aleutian Trench and is the type of fault that causes the earthquakes in this area.
fault
stress
earthquake
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4. Earthquakes occur along faults.
7.1
Earthquakes occur along faults.
Normal faults form as rocks are pulled apart.
Reverse faults form as rocks are pushed together.
fault
Strike-slip faults form as rocks are pushed horizontally in opposite directions.
stress
earthquake
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Explore animations showing fault motion.
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5. Earthquakes release energy.
7.2
Earthquakes release energy.
focus
epicenter
seismic wave
focus
epicenter
seismograph
Seismic waves move out from the focus in all directions.
VISUALIZATION
Explore primary-wave and secondary-wave motion.
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6. Earthquakes release energy.
7.2
Earthquakes release energy.
seismic wave
focus
epicenter
seismograph
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7. Earthquake damage can be reduced.
7.3
Earthquake damage can be reduced.
A powerful earthquake releases more energy and causes more shaking of the ground than does a weak earthquake. Both the Richter scale and the moment magnitude scale are often shown with a top value of 10, but neither actually has a maximum value.
aftershock
liquefaction
Magnitude
0–3.9
Very Minor to Minor
4.0–4.9
Light
5.0–5.9
Moderate
6.0–6.9
Strong
7.0–7.9
Major
Effects Near Epicenter
8.0 and above
Great
major to total destruction
rarely noticed
slight damage
some structures damaged
major damage to structures
some well-built structures destroyed
tsunami
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8. Earthquake damage can be reduced.
7.3
Earthquake damage can be reduced.
aftershock
An area’s risk of earthquakes can be predicted. The
strength of an earthquake depends in part on the
distance over which blocks of rock move.
kilometers
miles
liquefaction
tsunami
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9. Earthquake damage can be reduced.
7.3
Earthquake damage can be reduced.
aftershock
liquefaction
tsunami
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10. Earthquake damage can be reduced.
7.3
Earthquake damage can be reduced.
Structures can be designed for greater safety in an earthquake.
aftershock
liquefaction
tsunami
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11. 7.1 Earthquakes occur along faults. I. Earthquakes occur along faults.
A. Rocks move along faults.
stress
B. Faults are classified by how rocks move.
earthquake
1. Normal Faults
2. Reverse Faults
3. Strike-Slip Faults
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KEY CONCEPT
SUMMARY

12. Earthquakes release energy.
7.2
Earthquakes release energy.
II. Earthquakes release energy.
seismic wave
A. Energy from earthquakes travels through Earth.
focus
epicenter
1. Waves and Energy
seismograph
2. Primary Waves
3. Secondary Waves
4. Surface Waves
B. Seismic waves can be measured.
1. Using Seismographs
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2. Locating an Earthquake
KEY CONCEPT
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13. Earthquake damage can be reduced.
7.3
Earthquake damage can be reduced.
III. Earthquake damage can be reduced.
aftershock
A. Earthquakes can cause severe damage and loss of life.
liquefaction
1. Earthquake Magnitude
tsunami
2. Damage from Earthquakes
3. Damage from Tsunamis
B. Scientists work to monitor and predict earthquakes.
C. Structures can be designed to resist earthquake damage.
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SUMMARY

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