NATURAL NATURAL HAZARDSHAZARDS

EARTHQUAKESEARTHQUAKES

What are earthquakes and where do they occur?

Earthquakes are vibrations caused by earth movements at plate boundaries and at major fault lines (cracks in the earth’s surface).

They can occur at all 4 major plate boundaries but the most severe earthquakes are normally found at CONSERVATIVE and DESTRUCTIVE boundaries.

CONSERVATIVE

DESTRUCTIVE

Epicentre and focus

A seismograph

How can we measure earthquakes?

The largest earthquake ever recorded was in Chile. It measured 8.9 on the Richter Scale.

This measures the magnitude of a tremor (how powerful it is) using an instrument called a seismograph.

On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. Although the Richter Scale has no upper limit, the largest known shocks have had magnitudes in the 8.8 to 8.9 range. It is a logarithmic scale which means that a size ‘6’ on the Richter Scale is 10 times larger than a size ’5’ and 100 times larger than a size ‘4’.

1234

65

987

10

Richter Scale

The Richter Scale

Why do Earthquakes affect Why do Earthquakes affect different areas in different different areas in different

ways?ways? What are the reasons that earthquakes What are the reasons that earthquakes

may have different effects?may have different effects? What can be different?What can be different?

The number of deathsThe number of deaths The extent of the damageThe extent of the damage The cost of repairThe cost of repair (The social, environmental and economic effects)(The social, environmental and economic effects)

Earthquakes can have Earthquakes can have different effects on…different effects on…

1.1. Distance from the epicentreDistance from the epicentre

2.2. The state of preparation for an The state of preparation for an earthquakeearthquake

3.3. Population densityPopulation density

4.4. Type of land the area is built onType of land the area is built on

5.5. Time of the dayTime of the day

6.6. Time of the yearTime of the year

Copy and complete the boxes below using what you know about earthquakes. Think about the situation

where the most and least damage would be caused by an earthquakePowerful earthquake, Powerful earthquake, causes a lot of causes a lot of damagedamage

Weak earthquake,Weak earthquake,

Doesn’t cause Doesn’t cause much damagemuch damage

Distance from the Distance from the epicentreepicentre

The state of The state of preparation for an preparation for an earthquake (country) earthquake (country)

Population densityPopulation density

Type of land the area is Type of land the area is built onbuilt on

Time of the dayTime of the day

Time of the yearTime of the year

EARTHQUAKE EARTHQUAKE CASE STUDYCASE STUDY

CASE STUDYCASE STUDY : : KOBE EARTHQUAKEKOBE EARTHQUAKE

JAPANJAPAN17th JANUARY 199517th JANUARY 1995

Why did it happen ?Why did it happen ? How strong was it How strong was it What were the short and What were the short and

long term effects ?long term effects ? Why was it so severe ?Why was it so severe ?

Where is KOBE ?Where is KOBE ?

Mark the location of Kobe and Tokyo on your map

What happened at Kobe?What happened at Kobe? Look at p79 in People places and themes.Look at p79 in People places and themes. Read page 23 And page 24 And fill in the sheet Read page 23 And page 24 And fill in the sheet

carefullycarefully

Why did so many people die Why did so many people die in the Kobe earthquake?in the Kobe earthquake?

Use the writing frame to write an essay Use the writing frame to write an essay about why so many people died from this about why so many people died from this earthquake case study. earthquake case study.

Split it into sections on;Split it into sections on; The city of KobeThe city of Kobe The earthquakeThe earthquake Causes of the earthquakeCauses of the earthquake Effects on peopleEffects on people Effects on the cityEffects on the city Lessons that should be learned from the Lessons that should be learned from the

earthquakeearthquake

How can we try to manage How can we try to manage the effects of earthquakes? the effects of earthquakes?

This is the Sky Tower in Auckland, New Zealand.

Sky Tower is the tallest tower in the Southern Hemisphere and the twelfth tallest in the World.

Sky Tower is 328 metres tall (more than 1,076 feet); that's about 37 buses standing end on

end!

Sky Tower weighs 21 million kilos (20,000 tonnes) which is equivalent to 6,000 elephants.

Problem – Auckland is in an earthquake zone. How could you make buildings such as the Sky Tower more ‘earthquake proof’?

Sky’s the limit!

Sky Tower is constructed from a high strength, high performance concrete. The main structure of Sky Tower is a reinforced concrete shaft measuring 12 metres in diameter. It is supported by eight reinforced concrete 'legs' at the base, connected to the shaft by a concrete collar and designed to spread force load. Sky Tower's foundations go down more than 15 metres.The tower was tested to see if it would withstand earthquakes. Analysis shows that an earthquake measuring 7.0 on the Richter scale, located 40 kilometres from Sky Tower on the Kerepehi Fault, would leave Sky Tower essentially undamaged. In the extreme event of a magnitude 8.0 earthquake occurring within 20 kilometres of the tower, analysis shows that Sky Tower would remain standing.

What they did…

1. predict

water levels can rise in wells and lakes because of cracks in the rock

foreshocks before the main quake can be detected by a seismometer

animals can act strangely before the earthquake

a tiltmeter can check any movement within the rocks

Can earthquakes be predicted and controlled?

2. plan

What should people pack in their emergency kit?

make an emergency plan

organize regular ‘earthquake practices’ for offices and schools

advise people to plan for an earthquake (eg tell them to turn off the gas, find a ‘safe’ place in their homes, pack an emergency kit)

enforce regulations to make some buildings earthquake proof

Design a poster reminding people what to do in an earthquake.

How can we limit earthquake damage?

Earthquake proof Earthquake proof buildingsbuildings

Skyscraper Skyscraper modificationmodification A wide base leading up A wide base leading up

to a thinner point helps to a thinner point helps to channel vibrations to channel vibrations up and the building is up and the building is designed not to sway designed not to sway from side to side. from side to side.

Large scale dampers Large scale dampers can be placed on the can be placed on the bottom of buildings to bottom of buildings to help absorb the earth help absorb the earth vibrations. vibrations.

Earthquake proof Earthquake proof buildings buildings

Infill shear trussesInfill shear trusses Normally put onto Normally put onto

older buildings, this older buildings, this provides more strength provides more strength to the walls of the to the walls of the building as it shakes. building as it shakes.

How does this earthquake How does this earthquake protection idea work?protection idea work?

Steel ‘jackets’ Steel ‘jackets’

For a natural hazard that For a natural hazard that you have studied:you have studied:

1.1. Name and locate the eventName and locate the event

2.2. Using specific detail, explain the Using specific detail, explain the physical processes responsible for physical processes responsible for the eventthe event

3.3. Describe the methods used to Describe the methods used to predict this hazard eventpredict this hazard event 9 9 marksmarks