Download Earthquakes

V1/17-2016©
Earthquakes
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Overview
Scott Resource s presents Earthquakes: Understanding the Hazards, an informative overview of how earthquakes work, where
they occur and why they pose such ominous threats for millions of people around the world. The Teacher's Guide contains
vocabulary words defined in the context of the video, discussion points, and classroom activities designed to enhance the
videotape and create an interact time learning experience for students.
Vocabulary
STRESS - In geology, the force applied to a rock mass.
FAULT - A break in the Earth's crust along which there has been displacement of one side relative to the other.
EARTHQUAKE - An abrupt trembling of the ground caused by the sudden release of energy along a geologic fault below the
Earth's surface.
PLATE TECTONICS - A theory in geology that states the Earth's crust is composed of a mosaic of large, slowly moving plates.
CONVERGENT PLATE BOUNDARY - A boundary between tectonic plates characterized by faults that displace the Earth's crust
vertically.
SUBDUCTION ZONE - An elongated region of the Earth's crust where one tectonic plate moves below another resulting in
volcanoes and earthquakes.
REVERSE FAULT - A type of fault along which the plane of movement slants toward the uplifted side.
TRANSFORM FAULT BOUNDARY - A boundary between tectonic plates characterized by faults that displace the Earth's crust
horizontally. The plane of movement is nearly vertical.
SEISMIC WAVE - A form of energy that radiates from earthquakes.
FOCUS - In geology, the point within the Earth’s interior from which energy is released to cause an earthquake.
EPICENTER - The point on the Earth's surface directly above the focus of an earthquake.
PRIMARY WAVE - Also called P wave. The first and sharpest seismic wave felt when an earthquake occurs. P waves are
characterized by rapid pulses of compression and expansion.
SECONDARY WAVE - Also called S wave. The most damaging and long-lasting wave felt when an earthquake occurs. S waves are
characterized by the undulating motion of the Earth's surface.
MAGNITUDE - A numerical measurement of an earthquake's strength.
GROUND SHAKING - The violent shaking of objects during an earthquake.
LIQUEFACTION - An effect of earthquakes caused by the transformation of loose. wet, sandy soil into a dense liquid that cannot
support heavy objects.
GROUND RUPTURES - Cracks in the ground caused by the sudden shifting of bedrock or soil during an earthquake.
LANDSLIDE - An effect of earthquakes characterized by the rapid downslope movement of soil and rock along steep slopes.
TSUNAMI - A large, destructive ocean wave caused by the sudden displacement of the seafloor during an earthquake.
Serrata Pty Limited | 236A New Line Road, Dural, NSW, 2168 | 02 9651 3033 | www.serrata.com.au
V1/17-2016©
Discussion Points
1.
Explain what is meant by the statement. "Earthquakes do not kill people, buildings and bridges do." Why is it important
to make this distinction?
2. Although many people who live in places such as California are aware of earthquakes. they continue to remain there
despite the threat. Make a list of reasons why people might choose to live in earthquake country.
3. Each number on the earthquake magnitude scale represents a 30-fold increase in energy. How much more powerful
was the Alaska Earthquake of 1 964 with a magnitude of about 9 (M9) than the Northridge, California Earthquake of 1
994 with a magnitude of about 7 (M7)? Answer: M9 would be 30 times more powerful than Mg, and Ms would be 30
times more powerful than M7; therefore, M9 is 30x30 or 900 times more powerful than M7.
4. What is the relationship between the occurrence of earthquakes and the presence of active volcanoes? Are there
places where earthquakes occur without volcanoes? Give examples.
5. Why can't scientists predict earthquakes like they predict tomorrow 's weather?
6. Explain how earthquakes can be caused by the following events: Underground nuclear explosion, meteorite hitting the
Earth's surface, filling a large reservoir with water, large snow slide or avalanche, blasting in mine, volcanic eruption.
Which of these events occur naturally? Which are likely to produce the most damaging earthquakes?
7. Explain why a 6.9 magnitude earthquake in Russian Armenia killed 45,000 people while a 7. 1 earthquake near San
Francisco, California, killed only 67. (Hint: What factors other than magnitude determine an earthquake's destructive
power?)
8. Rank the following structures in order from most likely to least likely to survive the effects of a major earthquake:
Wood frame house, concrete reinforced apartment, adobe hut, brick building, tepee, mobile home, bridge.
9. Los Angeles and San Francisco lie 1 80 kilometres apart on opposite sides of the San Andreas Fault. The fault separates
two crustal plates which bring these two cities closer to each other at an average rate of 5 centimetres a year. How
many years will it take for the cities to meet? What forces cause this type of crustal motion?
10. In December 1 990, a businessman and non-geologist, lben Browning, incorrectly predicted that New Madrid, Missouri,
would experience a devastating earthquake. Schools closed, thousands of people panicked, and emergency services
were put on full alert over a 5-state area. Should non-scientists make such predictions public? In general, why are
scientists so cautious about making earthquake predictions?
Class Activities
1.
Refer to illustrations of faults in any Earth Science textbook or to the model shown in the video. Sketch the three major
kinds of faults: normal, reverse, and transform. Next make cardboard block models to demonstrate the actual
movement of each of the three types of faults.
2.
Demonstrate the motions of P and S waves by duplicating the spring toy experiment shown in the video. Preparation:
Students in pairs will need spring toys and a smooth surface, such as a floor or tabletop, to work on. One partner holds
one end of the extended spring toy while the other partner generates the "seismic waves:”
3.
Activity: Generate P waves using rapid push and pull movements; S waves using sideways whipping motions. Using the
same spring toy, what happens if both students generate P waves at the same time?
Serrata Pty Limited | 236A New Line Road, Dural, NSW, 2168 | 02 9651 3033 | www.serrata.com.au