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8.9.3 EARTHQUAKE SAFE STRUCTURES

 

 

Why is California Memorial Stadium called a “tectonic time bomb”?

The California Memorial Stadium is the home of football at the University of California, Berkeley. The site probably looked flat and easy to build on in 1922. But now scientists know that the Hayward Fault passes directly beneath both end zones. The stadium has been renovated in a $321 million project. The renovation involved 10 miles of steel cables, silicone fluid-filled shock absorbers, concrete piers, 3-feet of sand, plastic sheeting, and stone columns. Go Bears!

New Construction

New construction can be made safer in many ways:

  • Skyscrapers and other large structures built on soft ground must be anchored to bedrock. Sometimes the bedrock lies hundreds of meters below the ground surface.

  • The correct building materials must be used. Houses should bend and sway. Wood and steel are better than brick, stone, and adobe, which are brittle and will break.

  • Larger buildings must sway, but not so much that they touch nearby buildings. Counterweights and diagonal steel beams are used to hold down sway.

  • Large buildings can be placed on rollers so that they move with the ground.

  • Buildings may be placed on layers of steel and rubber to absorb the shock of the waves.

  • Connections, such as where the walls meet the foundation, must be made strong.

  • In a multi-story building, the first story must be well supported.

The Transamerica Building in San Francisco, pictured below, rests on a 52-foot deep steel and concrete foundation. Steel rods reinforce the building internally and X-shaped trusses support it externally. In the 1989 Loma Prieta earthquake, the building shook for more than a minute and swayed more than 12 inches in each direction, but was not damaged.

 

 

The Transamerica Pyramid in San Francisco is more stable in an earthquake or in high winds than a rectangular skyscraper.

Retrofitting

Older buildings can be made more earthquake safe by retrofitting . Steel or wood can be used to reinforce a building’s structure and its connections. Elevated freeways and bridges can also be retrofitted so that they do not collapse.

 

 

This bridge in San Diego, California, was built in 1931. It was retrofitted and reopened in 2010 to meet earthquake standards.

Preventing Fire Damage

Fires often cause more damage than the earthquake. Fires start because seismic wavesrupture gas and electrical lines. Breaks in water mains make it difficult to fight the fires (Figure below ). The shapes of pipes can make a big difference. Straight pipes will break in a quake. Builders zigzag pipes so that they bend and flex when the ground shakes. In San Francisco, water and gas pipelines are separated by valves. Areas can be isolated if one segment breaks.

 

 

In the 1906 San Francisco earthquake, fire was much more destructive than the ground shaking.

Making Choices

Strong, sturdy structures are expensive to build. Communities must decide how safe to make their buildings. They must weigh how great the hazard is, what different building strategies will cost, and how much risk they are willing to take.

See more here: http://science.kqed.org/quest/video/the-hayward-fault-predictable-peril/ .

 

 

Vocabulary

  • retrofit : Adding new technology to older systems.

Summary

  • New structures that are built to meet earthquake safety codes do much better inearthquakes.

  • Old buildings can be retrofitted for better safety.

  • Cost is an important factor in deciding how safe to make the structures in an area.

Practice

Use the resource below to answer the questions that follow.

 

 

  • What is LA’s most earthquake resistant building?

  • Why is this building chosen to be the safest?

  • Why is it called a floating building?

  • How many suspension points are in the building? How do they move?

  • What size earthquake should the building be able to withstand?

  • How far is it designed to move?

  • Why aren’t all buildings in Los Angeles designed like this?

Review

  • What can be done to make a new building safer in an earthquake zone?

  • What can be done to retrofit an older building in an earthquake zone?

  • What can be done to reduce the damage from fire after an earthquake?

  • Should all buildings in all areas be built to the highest earthquake standards? What is a more cost-effective approach?

 

STAYING SAFE IN AN EARTHQUAKE

 

 

How can you prepare for an earthquake?

If you live in earthquake country, the actions you take before, during, and after a quake could make the difference in your comfort for several days, or even your survival.

Protecting Yourself in an Earthquake

There are many things you can do to protect yourself before, during, and after an earthquake.

Before the Earthquake

  • Have an engineer evaluate the house for structural integrity. Make sure the separate pieces—floor, walls, roof, and foundation—are all well-attached to each other.

  • Bracket or brace brick chimneys to the roof.

  • Be sure that heavy objects are not stored in high places.

  • Secure water heaters all around and at the top and bottom.

  • Bolt heavy furniture onto walls with bolts, screws, or strap hinges.

  • Replace halogen and incandescent light bulbs with fluorescent bulbs to lessen fire risk.

  • Check to see that gas lines are made of flexible material so that they do not rupture. Any equipment that uses gas should be well-secured.

  • Everyone in the household should know how to shut off the gas line.

  • Prepare an earthquake kit with three days supply of water and food, a radio, andbatteries.

  • Place flashlights all over the house and in the glove box of your car.

  • Keep several fire extinguishers around the house to fight small fires.

  • Be sure to have a first aid kit. Everyone should know basic first aid and CPR.

  • Plan in advance how you will evacuate and where you will go. Do not plan on driving, as roadways will likely be damaged.

During the Earthquake

  • If you are in a building, get beneath a sturdy table, cover your head, and hold on.

  • Stay away from windows, mirrors, and large furniture.

  • If the building is structurally unsound, get outside as fast as possible.

  • If you are outside, run to an open area away from buildings and power lines that may fall.

  • If you are in a car, stay in the car and stay away from structures that might collapse, such as overpasses, bridges, or buildings.

After the Earthquake

  • Be aware that aftershocks , smaller quakes that come after the main trembler, are likely.

  • Avoid dangerous areas like hillsides that may experience a landslide.

  • Turn off water and power to your home.

  • Call 911 only if there is a real emergency. Many people will be trying to get through to emergency services.

  • Be prepared to wait for help or instructions. Assist others as necessary.

Vocabulary

  • aftershock : A smaller earthquake that follows the main quake.

Summary

  • Before an earthquake, be sure that your home is secure. Be sure that you have supplies to last a few days.

  • During an earthquake, get to a safe place.

  • After an earthquake, avoid dangerous situations, wait for instructions, and assist as necessary.

Practice

Use the resources below to answer the questions that follow.

 

 

  • When is California’s 4th season?

  • What should you do to prepare your home?

  • What should an emergency plan include?

  • What should you do when an earthquake hits and you are in your home?

  • What should be in your emergency kit?

  • What should you do if you are outside when an earthquake hits?

  • How should you organize your home?

Review

  • What should you do to prepare for an earthquake?

  • What should you do during an earthquake?

  • What should you do after an earthquake?

 

 

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