Transcript Earthquake Hazards and Safety

Earthquake Hazards and
Safety
Ch. 5.3
Objective
 Describe how earthquakes cause damage
and the kinds of damage they cause.
 Explain what can be done to reduce
earthquake hazards to buildings and to
people.
Engage/Explore
 What kinds of structures have you seen used
to make buildings, bridges, and highway
overpasses stronger?
 Do you think these structures would help
protect against damage in an earthquake?
Why, or why not?
Discover Activity
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Can Bracing Prevent Building Collapse?
Materials: 5 straws and tape
P. 162
What effect did the fifthe straw have? What
effect would a piece of cardboard taped to
the frame have? Based on your
observations, how would an earthquake
affect the frame of a house?
Reading Tip
Before you read preview the headings of the
section. Then predict some of the ways that
people can reduce earthquake hazards.
Notes - Promethean
1999 Earthquake
 Read p. 162
 Izmit, Turkey
 7.4 Moment
Magnitude
How Earthquakes Cause
Damage
 The severe shaking produced by seismic
waves can damage or destroy buildings and
bridges, topple utility poles, and fracture
gas and water mains.
 S waves can put stress on buildings to tear
them apart. Also trigger landslides or
avalanches.
 Local Soil Conditions - A house built on solid rock
will shake less than a house built on sandy soil.
 Liquefaction - occurs when an earthquake’s
violent shaking suddenly turns loose, soft soil into
liquid mud.
 Anchorage, Alaska earthquake in 1964 caused a
landslide that swept an entire housing
development down a cliff. Fig. 19
Question
 What are some questions people might ask
before building a house in an area that is at
risk for earthquakes?
 Aftershocks - an earthquake that occurs
after a larger earthquake in the same area.
May strike hours, days, or even months
later.
 Japanese homes are built of wood with
paper walls. How do you think this kind of
construction would stand up to an
earthquake?
 Tsunamis - when an earthquake jolts the ocean
floor, plate movement causes the ocean floor to
rise slightly and push water out of its way. If the
earthquake is strong enough, the water displaced
by the quake forms large waves.
 P. 164, Fig. 20 - They begin as a low wave, but
turn into a huge wave as it nears the shore.
Questions
 What are the major
causes of earthquake
damage?
 Shaking caused by
seismic waves.
 Local soil conditions
 Liquefaction
 Aftershocks
 Tsunamis
Making Buildings Safer
 New buildings must be made stronger and
more flexible. Older buildings must be
made stronger and more flexible.
 P. 165 Exploring an Earthquake-Safe House
 Which of these steps could easily be done
after the house is built.
Answer: F & H
 Construction Methods  Base-isolated building is a building designed to
reduce the amount of energy that reaches the
building during an earthquake. Figure 22
 Cause floods and fire when gas pipes and water
mains break.
 Flexible joints and automatic shut off valves
can be installed.
Protecting Yourself During an
Earthquake
 Drop, cover, and hold. Fig 23A
 Crouch against inner walls avoiding
windows, mirrors, wall hangings, and
furniture.
 Outdoors - move to a playground. Avoid
vehicles, power lines, trees, and buildings.
Sit down to avoid being thrown down.
 After earthquakes, water and power failures.
Stores closed, travel is difficult.
 You may have to wait several days.
 Prepare an earthquake kit - canned food,
water, first aid supplies, stored where it is
easy to reach.