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EARTHQUAKES

1. What are earthquakes?

Earthquakes are the sudden vibrations of the earth surface due to the collision of

plates. The rocks at the edges of these plates are ruptured into faults and the

sudden movement results in earthquakes.

2. What is the distribution of the world’s earthquakes?

(a) The Circum- Pacific belt – the Ring of Fire Coincides with the young fold mountain belts on the east and west rims of the

Pacific Ocean

In zones of colliding plates and sliding plates

Accounts for over 68% of all earthquakes

(b) The Mediterranean- North India belt

SM SAYYIDINA OTHMAN, TUTONG

EARTHQUAKES

Coincides with the belt of young fold mountains stretching from the Himalayas

to the Alps and the Mediterranean region

In a zone of colliding plates

Experience 21% of all earthquakes

(c) Belts of minor earthquake activity, include

The mid- Atlantic belt, which coincides with the belt of volcanic islands and

oceanic ridges in the Atlantic Oceans, and is in a zone of diverging plates

beneath an ocean

The East African rift Valley, which is a zone of diverging plates beneath a

continent

Together account for 11% of all earthquakes.

3. Why earthquakes occur (cause of earthquakes)?

Earthquakes are caused by the movement of the earth's tectonic plates.

Earthquakes occur where the earth's plates meet along plate boundaries.


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For example as two plates move towards each other, one can be pushed

down under the other one into the mantle. If this plate gets stuck, it causes

a lot of pressure on surrounding rocks. When this pressure is released it

produces shock waves. These are called seismic waves. This is an

earthquake. The waves spread out from the point where the earthquake

started - the focus. More damage is done near the focus. The point on the

earth's surface directly above the focus is the epicentre.

4. Measuring Earthquakes

The magnitude (size) of an earthquake is measured using a seismometer.

This is a machine that measures movements in the earth's surface.

A seismometer

The Richter Scale (ranges from 0 to 9) measures earthquakes on a

logarithmic scale - this means that an earthquake of 6 is ten times more

powerful than one with a score of 5.

5. Key terms


http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/RichterScale.html

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Fault- is a break in the rocks that make up the Earth’s crust, along which

rocks on either side have moved past each other.

Focus- the point in the earth’s crust where an earthquake originates

Richter Scale- A measure of earthquake intensity on seismographs

Epicenter- the point on the earth surface which receives the strongest

shock waves. It is directly above the focus.

Tremor- a shaking or vibrating movement of the earth

Seismic waves- are vibrations that travel through the Earth carrying the

energy released during earthquakes.

Summary


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Cause of earthquake

The movement of

the earth's tectonic plates.

World distribution

(a) The Circum- Pacific

belt – the Ring of Fire

(b) The Mediterranean

- North India belt

(c) Belts of minor

earthquake activity

Definition

Sudden vibrations of

the earth surface due

to the collision of plates.

Measurement of earthquake

magnitude (size)

Using seismometer

read in Richter scale on a

seismograph

Key terms

1. Fault2. Focus3. Richter scale4. Epicenter5. Tremor6. Seismic

wave

EARTHQUAKES

IMPACT OF EARTHQUAKES AND TSUNAMI ON PEOPLE AND THE ENVIRONMENT

Earthquakes can bring about great loss of life and damage to property. The

strong ground vibrations caused many buildings to collapse. Gas mains were

broken and immediately after earthquake, fires broke out, causing further

damage.

The table below shows the three types of effects of earthquake and tsunami

on people and the environment.

The primary effects The secondary effects The long-term effects


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The shaking caused

buildings to collapse,

signs to fall off walls,

windows to shatter, furniture to fall over, roads to crack, bridges to topple. All

these are primary

effects. They caused

injury and death.

For example, in

Kashmir, over 79000

people were killed, 100

000 were injured, and

3.3 million homes were

destroyed by the

primary effects. There

were large cracks in the

ground surface, and

landslides. The effects

were so serious in

Kashmir because the

buildings in the towns

and villages weren’t built

very strongly.

These are effects that

happen later. They can

be fires caused by

broken gas pipes, or

disease caused by

dead bodies that aren’t

buried, and also by

sewerage pipes bursting

and contaminating water supplies.

For example, in

Kashmir, the secondary

effects included

diseases (mainly

diarrhea) spread from

contaminated water

supplies, and also

respiratory infections

like pneumonia. People

also died of cold in the

harsh winter, because

they only had thin tents

to live in.

These are things that

continue to be a

problem for a long time.

They can be social, economic and environmental. For

example in Kashmir, the

main long-term effects

were:

In rural areas the crops

mostly survived and so

did the animals. So

farmers could continue

their jobs and the

markets re-opened

quickly. But in the urban

areas, lots of people lost their jobs as their offices or shops were damaged.

Electricity lines were brought down, so

reconstruction was

made harder.

Schools were damaged and students lost their books.


EARTHQUAKES

3.3 million people lost their homes and were

forced to live in temporary shelters

until rebuilding could

start in the spring.

Case Study: Japan Earthquake and Tsunami (11th March 2011)

The Japan earthquake occurred on the 11th March 2011. It was the largest earthquake that they have had since records began. It was originally measured

as a 8.9 magnitude earthquake but this was later increased to a magnitude 9.0 as

more detailed readings came in from seismographs and other equipment.

The Japan earthquake was absolutely devastating. The earthquake itself, although

much bigger than usually seen in Japan, was prepared for extensively as

they receive many earthquakes every year. What was not adequately prepared for

was a tsunami of such scale. Many of the tsunami walls protecting coastline villages

were around 7 meters high, nowhere near big enough to stop the 10 meter high wall of water (the height of a three storey building) that hit the coasts around 30 minutes

after the earthquake. This caused many thousands of Japan earthquake victims.

The Tsunami approaching Japan:


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There have been over 11,000 Japan earthquake victims so far (as of

30/03/11), with over 17,000 still missing - many of which will also be dead.

The predicted death toll is 18,000 however this is likely to increase.


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There are currently 244,000 refugees who are seeking shelter in the

Japanese earthquake relief camps. With many children still unable to find their

parents it is worried that the majority may be 'Japan earthquake orphans'. The

question therefore lies in what to do with them, foreigners looking to adopt

have been turned down as Japan wants to keep them in their home country

and culture. (Contrasting the Haiti orphan crisis)


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The tsunami caused a near catastrophic meltdown of a nuclear power plant

which exploded multiple times and released radioactive material into the air

causing dangerous levels in foodstuffs grown within tens of kilometers.


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The water supply in many areas is unsafe to drink due to radioactivity and

some of the plant workers risking their lives to cool the plant's core were

exposed to massive overdoses and are now in hospital. Japan earthquake

relief organizations have been handing out water bottles to survivors.

Boats were dragged inland and left deserted, houses were ripped from their

foundations and scattered among the remains of others, some even stacked

on top of each other.


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Summary

Impact of earthquakes and tsunami on people and the environment


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EARTHQUAKES

Death and injuries

Homeless

Collapse of building

Windows shatter

Roads crack

Bridges topple

Fractured gas pipes and water mains

Fire caused by broken gas pipes

Disease spreads by dead bodies and contaminated water

Landslides

Tidal waves

Loss of jobs

Cut off of electricity

Rebuilding of Schools

Rebuilding of home

Loss of family members

Air Pollution

Land Pollution

STRATEGIES TO REDUCE THE IMPACT OF EARTHQUAKE


EARTHQUAKES

There are a number of strategies that can be used to reduce the impact of earthquakes.

Install adequate warning systems.

The use of special sensing equipment and devices with effective

communication systems which are linked to government agencies, rescue

and emergency services, and the public should be put in place to warn

people on earthquake occurrences.

- Seismograph

- A seismograph is an example of a device and instrument that detect the

earth's movement and vibrations.

- A seismograph consists of a ground motion detection sensor called a

seismometer, coupled with a recording system.

Seismograph

- Seismometers help in monitoring the frequency of the Earth's vibrations

and detect the development of tsunami. The monitoring and predictions

made by seismometer provide crucial information so that people living in

affected areas can be warned and evacuated before a disaster strike


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Graph obtained from seismograph


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Example:

In December 2004, a massive earthquake occurred off the coast of Sumatra, killing

tens of thousands of people living in countries where there were no tsunami warning

systems. The government of Indonesia is now developing a warning system to

prevent a similar tragedy. Japan and the western United States have well-developed

tsunami warning systems, should a quake occur offshore of those areas.

Construct Earthquake -Resistant Buildings - Earthquake resistant buildings can be constructed in areas with frequent

earthquakes.

Earthquake resistant house

SM SAYYIDINA ‘OTHMAN, TUTONG

EARTHQUAKES

'Quake proof' Houses

- The earthquake resistant buildings are built with deep foundations with

rubber shock absorbers and concrete reinforced with steel. They are designed

to twist, sway and have sprinkler systems and gas cut off valves.


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Earthquake resistant building

- In some many earthquake resistant buildings, technologies and structural

modifications are used to protect buildings from damaging earthquake effects.

- Technologies such as Base Isolation Devices, Seismic Isolation systems,

Seismic Dampers and Energy Dissipation Device are used.

- The base isolation is to detach (isolate) the building from the ground in such a

way that earthquake motions are not transmitted up through the building or at

least greatly reduced.

- Seismic dampers are special devices introduced in the building to absorb

the energy provided by the ground motion to the building (much like the way

shock absorbers in motor vehicles absorb the impacts due to undulations of

the road).


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Building structures designed to withstand earthquakes


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Educate and provide information to the public before, during and after the earthquake strikes.

This can involve the use of radio, TV and newspapers. Everyone should know

(i) What precautions they need to take for the own safety and for the safety

of others.

(ii) How to secure their home and belongings against damage.

(iii) What to do before, during and after an earthquake.

Use of Technology to prevent Fire Hazards

Electronic systems can be installed to cut off electricity and gas supplies

automatically during an earthquake. This would minimize the danger of fire

caused by 'live' wires or bursting of gas pipes.

Earthquakes drills.

- These are held to practice what to do in the event of an earthquake taking

place such as the one held in Japan on Sept 1st every year.

- Earthquake drills should be carried out in schools, offices and homes on a

regular basis


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Have a unified plan of action.

Time is important in the case of major disasters. Delay in support and action

can result in many deaths. Local, national and international support services

should know exactly what to do, and how to work together to produce a rapid,

efficient and effective support system, that is, by forming Community

Emergency Response Teams (CERT)

- The Community Emergency Response Team (CERT) Program educates

people about disaster preparedness for hazards that may impact their area

and trains them in basic disaster response skills, such as fire safety, light

search and rescue, team organization, and disaster medical operations.

- Using the training learned in the classroom and during exercises, CERT

members can assist others in their neighborhood or workplace following an

event when professional responders are not immediately available to help.

- CERT members also are encouraged to support emergency response

agencies by taking a more active role in emergency preparedness projects in

their community.


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Emergency plans.

These are drawn up, supplies such a bottled water, medicines and tinned

food are stockpiles by individuals or local areas.

Provide rapid and efficient support system after an earthquake.

- Medical assistance, food, medicine and accommodation are needed fast

after an earthquake. These supplies should come as quickly as possible

which can reduce the number of deaths.

- Heavy duty machines are also needed to reduce the time taken to achieve

rescues.


EARTHQUAKES

Summary

STRATEGIES TO REDUCE

THE IMPACT OF EARTHQUAKES


Technologies to prevent fire hazards

Efficient and rapid support system

Unified plan of actions

Build earthquake resistant buildings

Install adequate warning systems

Emergency drills

Educate and inform public on

earthquakes

Emergency plans

EARTHQUAKES

The following differences between LEDC and MEDC need to be considered:

MEDCS LEDCS

1. Health

care

Have the medical resources and

money to quickly get appropriate aid

to areas after a natural disaster.

Rely on aid from overseas as their

health system, which is

inadequate. This overseas aid

takes time to arrive.

2.

Emergency

services

and

Education

Such as Japan and New Zealand,

there are well thought out

emergency procedures:-

The government departments

responsible for managing and

coordinating emergency responses,

and for educating the public about

natural hazards.

In Japan regular earthquake drills

are held in schools and places of

work, and every year a full-scale

practise for armed forces and

emergency services is held.

Emergency services actually

practice through simulations, so they

know exactly what they should do if

disaster strikes.

Do not have these emergency

plans, and so far more damage

can be done before the emergency

services reach the area.

The remoteness of some areas

made it difficult for authorities to

monitor and to educate the people.

3. Building

technology

Japan and the United States

developing buildings that have more

chance of resisting an earthquake:-

Don't tend to have the technology

available or money to pay for it,

and so often their buildings are


WHY STRATEGIES USED TO REDUCE THE IMPACT OF EARTHQUAKES MAY BE LESS EFFECTIVE IN LEDCS THAN MEDCS

EARTHQUAKES

Most houses in San Francisco are

made of wood, to make them more

flexible and allow them to move with

the quake.

Larger skyscrapers are built with

flexible foundations, (shock

absorbers) which allow them to sway

during a quake, rather than being

rigid and falling down.

Many countries in areas prone to

natural hazards have building codes

to say where they can and cannot

build, and how high the buildings can

be.

In 1995, the Kobe earthquake hit in

Japan. Measuring 7.2 on the Richter

scale it had the potential to cause

massive damage to vulnerable

buildings, but because many

buildings were designed to withstand

earthquakes, only 5500 people were

killed.

very susceptible to earthquakes.

Communication systems may be

underdeveloped, so the population

may not be well educated about

what to do in the event of an

earthquake.

Construction standards tend to be

poor in LEDCs. Homes and other

buildings may suffer serious

damage when a disaster occurs.

Buildings collapsing can cause

high death tolls.

In contrast to the Kobe earthquake

that killed 5500, an earthquake of a

slightly smaller intensity hit Gujarat

in India in 2001. It killed

20 000 people.

4.

Scientific

prediction

Have scientists to monitor and

planted a huge number of

seismographs in the ground to try to

detect even the faintest of tremors.

No investment in research and

development. Therefore, no

qualified scientist and limited or no

number of seismograph to detect

tremors.


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Allows the sufficient time to evacuate

people from the danger area.

Evacuation and other emergency

plans can be difficult to put into

action due to limited funds and

resources

No time to evacuate people.

5.

Recovery

Able to recover quickly from a

natural disaster, due to having the

investment and technology needed

to return the area to as good as new

as soon as possible.

They can afford to allocate funds to

'just in case' measures. They keep

emergency stocks of medicines,

tents, blankets, food, water, and

communications equipment. It's kept

ready for use and constantly

updated. MEDC's have the

resources close at hand and can be

sending them out within hours.

Because LEDC's often have to rely

on aid from overseas, this quick

recovery is often impossible for

them.

Clearing up can be difficult. There

may not be enough money to

rebuild homes quickly and safely.

Many people could be forced to

live in emergency housing or

refugee camps.

Many LEDC's struggle to provide

these facilities for normal use let

alone keep a spare set of

everything in case of disasters.

The speed with which these

resources reach an area is critical

to reducing deaths.

By contrast, LEDC's often have to

ask for help, and mobilising

international aid can take days. As

a result people die from diseases

as they have no fresh supplies.


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Summary

WHY STRATEGIES USED TO REDUCE THE IMPACT OF EARTHQUAKES MAY BE LESS

EFFECTIVE IN LEDCS THAN MEDCS?

Because the following factors are different in the LEDCS and MEDCS


Building technology

Emergency services and

education

Health care

Scientific prediction

Recovery

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