earthquakes - ermysted's grammar school

© Boardworks Ltd 20031 of 27

Earthquakes


Most slides contain notes to accompany the presentation.

This icon indicates that the notes contain particularly

detailed instructions or extension activities.

To access these notes go to ‘Notes Page View’ (PowerPoint

97) or ‘Normal View’ (PowerPoint 2000/2002).

Normal ViewNotes Page View

This icon indicates that a Flash file has been

embedded into the PowerPoint slide. These files are

not editable.

Teacher’s notes and Flash files


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


Why do earthquakes happen?


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

RichterScale

The Richter Scale


The Japanese earthquake in Kobe

(September 1995) measured 7.2 on the

Richter Scale.

The Greek earthquake (June 1995)

measured 6.2 on the Richter Scale.

How many times greater was the Japanese earthquake?

How can we measure earthquakes?

1234

65

987

10

RichterScale


A seismograph


Mercalli Scale

This measures

how much

damage is

caused by the

earthquake

based on

observations. It

is measured on a

scale between I

and XII.

Mercalli Scale


I Felt by almost no one.

II Felt by very few people.

III Tremor noticed by many, but they often do not realise it is an

earthquake.

IV Felt indoors by many. Feels like a truck has struck the building.

V Felt by everyone; many people are awakened. Swaying trees and

poles may be observed.

VI Felt by all; many people run outdoors. Furniture is moved.

VII Everyone runs outdoors. Poorly built structures considerably

damaged. Slight damage elsewhere.

VII Specially designed structures damaged slightly, others collapsed.

IX All buildings considerably damaged, many shift off foundations.

Noticeable cracks in the ground.

X Many structures destroyed. Ground badly cracked.

XI Almost all structures fall. Bridges wrecked.

XII Total destruction. Waves seen on ground surfaces, objects are

tumbled and tossed.

Activity

Design your own cartoon based on the Mercalli Scale

descriptions below.


Epicentre and focus


Focus

Epicentre

An earthquake has occurred along this fault line.

Match the letter with the correct label.

Epicentre and focus


An earthquake has occurred in this area.

Which area (the town or the forest) will receive the stronger

earthquake?

Which area will receive more damage from the earthquake?

Epicentre and focus


predict plan protect

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

How can we limit earthquake damage?


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?


This is San Francisco in the USA.

Why does this skyscraper have a wide base?


deep foundations

strong lintels

overlapping bricks

What other measures would make buildings less likely to

collapse in an earthquake?

Building regulations in earthquake zones


Which shape of building would be most ‘earthquake proof’?


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…


Turkish earthquake (August 1999)

The magnitude of the earthquake was higher

than first thought, measuring 7.4 on the Richter

Scale. Seismologists expect a large number of

aftershocks, possibly for up to a year. These

could bring down the damaged buildings.

The search continues for survivors, but

temperatures, 30ºC in the day and 10ºC at

night, are far from ideal. International rescue

teams carry on searching for up to 72 hours

after a disaster, but it has been known for

people to survive much longer than this. The

longest survival is 17 days by a Korean who

chewed cardboard and drank his own urine

before being rescued.

Fact File

(3 days after the

earthquake)

Dead : 10,059

Missing : up to 35,000

Injured : over 45,000


You are in charge of the earthquake task force in Turkey.

It is three days after the earthquake.

Put these problems in the order of urgency. Explain your

choice.

Organize emergency hospital to look after injured

Search for more survivors

Bury the dead Stabilize the damaged buildings

Organize emergency camps and supplies for the survivors

Turkish earthquake (August 1999)


If the epicentre of an earthquake is at ‘A’, which settlement

will be damaged the most? Give reasons for your answer.


Factors affecting the damage caused by earthquakes

size of the earthquake

time of day

emergency services

building design and construction

education

physical landscape

1) Which factor/s do you think are the most important?

2) Which factors are related to the wealth of the country?

3) How can the education of the population affect the

amount of damage caused by an earthquake?


Read the following two slides.

Compare the earthquake in Los Angeles (94) with the

earthquake in Turkey (99) using the following table (you will

need an atlas to help with your research).

Why were there more deaths in the Turkish earthquake?

size of the earthquake

time of day

emergency services

building design and construction

GNP (wealth)

number of deaths

education

Los Angeles Turkey


Earthquake struck on holiday honouring Dr Martin

Luther King….57 dead

Fires burned out of control last night after a devastating earthquake

measuring 6.6 on the Richter Scale hit LA. Over fifty people have

been killed including fourteen people trapped in a collapsed bock

of flats, near the epicentre, in the district of Northridge. Reports

suggest that over one thousand people are injured and

the city is at a standstill. Freeways have buckled, trains have been

derailed and the airport is closed. The earthquake struck before

dawn and was felt over a wide area. The quake was felt as far

away as Las Vegas, 125 miles away to the east!

Emergency shelters have been set up by the Salvation Army and

the Red Cross. In addition, twelve search and rescue teams and

four medical teams have been sent to the quake zone. The teams

are using dogs, sensitive listening devices and tunnelling

equipment to look for survivors.

Los Angeles earthquake (1/94)


Turkey earthquake (8/99)

Izmit buildings substandard

The earthquake that hit Turkey last month has resulted in an estimated death

toll of between 30,000 and 40,000. The earthquake that measured 7.4 on the

Richter Scale, struck at 3am. It had an epicentre approximately 11 km to the

south east of Izmit and it was felt as far as 320km away.

Turkey received international help to rescue the thousands trapped in collapsed

buildings. At least 20,000 buildings collapsed or suffered heavy damage. The

buildings which collapsed were mainly between 6 and 8 stories high and had

been built in the last few years. Although new buildings in earthquake areas are

supposed to follow the ‘Uniform Buildings Code’ (California), many of these

buildings were poorly constructed in concrete and had unreinforced masonry

walls.

Concerns were also raised over the fact that the Tupras oil refinery in Korfez

was allowed to be built so close to the North Anatolian Fault. The oil refinery

burned out of control for several days after the earthquake. The fault has

produced seven earthquakes with a magnitude of more than ‘7’ on the Richter

Scale since 1939.

earthquakes - ermysted's grammar school

Documents