Epicentre

Seismic waves

Focus

Plate movement

Reducing the effects of earthquakes:

We can't stop an earthquake from happening, and it is

very difficult to predict exactly when an earthquake will

occur. However, we can try to limit the damage...

Building design: Buildings sway as the energy of a

quake’s waves moves through them. As a result many

new buildings in developed countries are earthquake-

proof, and older buildings can be retrofitted to strengthen

them (this means adding new technology to existing

buildings).

Flexibility is important

Wood and steel have more give than, unreinforced concrete.

Skyscrapers everywhere must be reinforced to withstand strong forces

from high winds, but in quake zones, engineers must design structures

that can absorb the energy of the waves throughout the height of the

building. Floors and walls can be constructed to transfer the shaking

energy downward through the building and back to the ground. The

joints between supportive parts of a building can be reinforced to

tolerate being misshapen by earthquake forces.

Watch the video clip to see the flexibility…

Liquefaction:

As seismic waves pass through the earth, rock absorbs more energy

than sandy soils or landfill, so buildings on solid rock will be much less

affected than those built on softer soils. If softer soils have water in

them, they can become a little like quicksand during an earthquake.

When seismic waves pass through saturated soil, they give it a strong squeeze. The soil loses its strength and behaves like a liquid, a process

called liquefaction. Buildings on top of liquefied soil often topple.

San Francisco:

Seismograms taken

at the same time in

locations less than

1100 feet from

each other. One

location is on solid

bedrock, the other

is on landfill.

- Can you work out

which is which?

Reducing the force a building is subjected to - install base

isolators, which isolate the base of the building from the

earth's movements.

1) Giant hockey pucks that squish and deform as the building

rocks on top of them, absorbing some of the energy of the

shaking.

2) Two horizontal surfaces, that slide past each other. The

building sits on the top plates, the bottom plates rest on the

ground. Only the bottom plate moves, sliding back and forth.

1. Computer controlled movable

roof weights to counter the

shock waves.

2. Cross – bracing to give added

strength and prevent twisting.

3. Automatic window shutters to

prevent falling glass.

4. Sheer core of reinforced

concrete and tensioned

cables around lift shaft.

5. Automatic sprinkler system

and gas shut-off to prevent

fires.

6. Strengthened steel and

reinforced concrete road

supports.

7. Foundations set deep into the

ground.

8. Rubber shock absorbers.

9. Base isolator allows sideways

motion.

-What is retrofitting?

-How can ‘Quake-

wrapping’ reduce the

effects of an

earthquake?

• How might building design in a

developed country compare to

that of a developing country?

Appropriate technology

Many developing countries are not able to invest in the retrofitting of

old buildings or constructing earthquake-proofed new structures.

Appropriate technology is necessary - designed with consideration

of the community it is intended for.

Over 1 billion people in the world live in bamboo houses.

Why?

-very strong

-bends easily

Bamboo is being used in Costa Rica (70 hectares of bamboo

plantation will build 1000 houses). In 2009, after a strong earthquake,

all 30 bamboo houses at the epicentre of the 7.6 magnitude

earthquake survived without any damage while many of the

concrete homes and hotels around them collapsed.

Gujarat, India

Earthquake-

resistant house

Local and

Recycled, how?

Explain why the building

methods used in Costa Rica and

Gujarat, India are appropriate

and sustainable.

Costa Rica and India are developing countries and

cannot afford the technology used to build new

earthquake-proof buildings or modify older buildings.

Therefore they use materials that they can find locally

such as bamboo. Bamboo is very strong and can bend

easily. This means that it is a good building material for

an earthquake. Bamboo is readily available and a lot

less land is needed to grow it, compared to timber. In

India, local and recycled materials are used to build

earthquake-resistant houses.

• Suggest how the

damaging effects of

earthquakes on buildings

can be reduced (4)

Self assessment

• Level 1 (Basic) 1-2 marks

• They have listed simple statements without giving much detail.

• E.g. build bamboo houses, retrofitting, building codes. Ideas

on ‘strengthening the building’ must be qualified.

• Level 2 (Clear) 3-4 marks

• Clear descriptions with development of ideas.

• E.g. “They could build earthquake proof buildings with X

structures to prevent twisting. They could build strengthened

housing that will not collapse when an earthquake strikes as

they are flexible and move with the shockwaves”, etc.

• One extra mark if they have used their own knowledge -

reinforced glass/ window shutters acceptable as methods.

They must explain that they reduce damage to buildings not

people e.g. falling glass.

Earthquake preparedness

If people are aware of what they should

do before, during and after an

earthquake, the number of casualties

and the damage caused can be

reduced.

-Regular earthquake drills: In California

whole communities once per year. ‘The

Great California Shakeout’ helps

residents to prepare for 'The Big One'.

While you’re watching these videos,

think how the people of Haiti might

prepare for earthquakes differently…

Japan – ‘Disaster

Prevention Day’, 1st

September each year.

The date is significant

because of the Great

Kanto earthquake, which

struck Tokyo in 1923.

Design a poster

that highlights

how people

should prepare

for earthquakes

Consider:

-what to do before,

during and after

the earthquake

-where they are:

indoors, outdoors etc.

If you are: Then:

Indoors

- Take cover under a sturdy desk, table, or bench or against an inside wall, and

hold on. If there isn’t a table or desk near you, cover your face and head with

your arms and crouch in an inside corner of the building.

- Stay away from glass, windows, outside doors and walls, and anything that

could fall, such as lighting fixtures or furniture.

- Stay in bed - if you are there when the earthquake strikes - hold on and protect

your head with a pillow, unless you are under a heavy light fixture that could fall.

In that case, move to the nearest safe place.

- Use a doorway for shelter only if it is in close proximity to you and if you know it

is a strongly supported, loadbearing doorway.

- Stay inside until shaking stops and it is safe to go outside. Most injuries during

earthquakes occur when people are hit by falling objects when entering into or

exiting from buildings.

- DO NOT use the elevators.

Outdoors- Stay there.

- Move away from buildings, streetlights, and utility wires.

In a

moving

vehicle

- Stop as quickly as safety permits and stay in the vehicle. Avoid stopping near

or under buildings, trees, overpasses, and utility wires.

- Proceed cautiously once the earthquake has stopped, watching for road and

bridge damage.

Trapped

under

debris

- Do not light a match.· Do not move about or kick up dust.

- Cover your mouth with a handkerchief or clothing.

- Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is

available.

- Shout only as a last resort - shouting can cause you to inhale dangerous

amounts of dust.

How can an

earthquake

shaking map

benefit people?

Think of two

reasons

risk / protection /

building codes /

liquefaction / earthquake proofing

Earthquake shaking map of Sicily

An earthquake survival kit…

Fire ExtinguisherFirst Aid Kit Swiss Army Knife

Plastic bucketTorch TV

Board gamesMatches Candles

Tin openerSpade Small tent

4 litres mineral water Water purifying tablets Toilet paper

Radio (battery

operated)Toothpaste Mobile phone

DisinfectantTools including pipe

wrenchSpare batteries

BatteriesTinned food Dried food

Dust maskSpade Blankets

Avalanche transmitter Wind up radioCamping gas and

stove