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 • 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.
What are the major causes of earthquake damage? Shaking caused by seismic waves. Local soil conditions Liquefaction Aftershocks Tsunamis Questions
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.