Eq and tsunamis

• An earthquake is a vibration in the earth’s crust caused by the sudden release of stored energy in the rocks found along fault lines.

Earthquakes

The distribution of the earth’s major earthquakes

Hazards associated with living in earthquakes zones

- Disruption of services

- Destruction of properties

- Landslides

- Destruction of infrastructure

- Threat of tsunamis

- Loss of lives

- Fires

SPLIT LIKE FLOWER

Earthquakes

Disruption of services• An earthquake can

disrupt services such as the supply of electricity, gas and water.

• The earthquake in Kobe, Japan, in 1995 disrupted electricity, gas and water supplies to about a million of Kobe city’s 1.4 million residents.

Hazards associated with earthquakes

Fire

• Earthquakes may rupture gas pipes and this can provide fuel to start fires.

• For example, the earthquake in Kobe, Japan, in 1995 caused extensive fires.


Children stand near houses in Padang, Indonesia that caught fire after the earthquake

Landslides• Landslides are

rapid downslope movements of soil, rock and vegetation.

• Mudflows may also occur when there is heavy rainfall.


Damage Caused by Offshore Earthquake Near World's Largest Nuclear Power Plant in Japan in 2008

Destruction of properties

• Earthquakes can cause destruction to many homes.

• People may be without homes after the disaster.


(Kobe, Japan earthquake)


Destruction of infrastructure Earthquakes may cause cracks to form in infrastructure such as roads and bridges.

Transportation can be disrupted as it is unsafe to use the damaged roads.

Loss of lives

• Earthquakes and their associated hazards often threaten the lives of those living in earthquake zones.


A person approaches a body lying in the rubble along Delmas road, the day after an earthquake struck Port-au-Prince, Haiti.

A 7.0-magnitude earthquake, the largest ever recorded in the area, rocked Haiti on Jan 2010.

Case study: Earthquake in Tōhoku, JapanWhat are the effects of the earthquake on people and the environment?

• Occurred in 2011• Generated large tsunami• Destroyed the Fukushima

nuclear power plant

Case study: Earthquake in Tōhoku, JapanHow have people responded to the earthquake ?

• Sent out 100,000 members of the Self-Defence Forces

• Set up rescue centres• The bank of Japan pumped

US$183 billion into the economy.

• Trained personnel dealt with post anxiety and depression.

• Extent of earthquakes - The Richter Scale is used to measure the magnitude

of an earthquake

• Measuring earthquakes

- A seismograph records the seismic waves released by an earthquake.

• Apart from its magnitude, the extent of damage caused by an earthquake may vary based on other factors: - Population density

- time of occurrence

- level of preparedness

- distance from the epicentre

- type of soil

Earthquakes

Definition More severe Less severe

Population density

Number of people living in the area

Dense population eg city

Less dense population eg countryside

Level of preparedness

Evacuation plans, trained rescue workers

Not prepared Prepared eg Emergency Drills

Distance from epicentre

Point on the earth's surface vertically above the focus of an EQ

Nearer the epicentre eg Christchurch, NZ 2011

Further away from epicentre

Time of occurrence

Time of occurrence Day hours Night hours (sleeping, more deaths)

Types of soil Liquefaction: ground becomes unstable and soil flows like liquid

Loose and unconsolidated sediments

Stable and consolidated soil

P67

• Seismic wave• Distance to the surface• Built up area• Time it occurred• Magnitude of earthquake

• In 2011, Christchurch is within the first seismic wave which is very near to the epicenter of the earthquake, while in 2010, Christchurch is at the third seismic wave.

• In 2011, the earthquake occurred very near to the surface at a focal depth of 5km so the impact is greater.

• Christchurch is a densely built up area with many buildings and the infrastructure is not built to withstand the stronger vibration felt in 2011.

• In 2011, earthquake occurred at 12.51pm where many people are still in offices working when buildings collapsed, while in 2010 at 4.35am, when most people are not in high-rise offices.

• Magnitude : 2011 – 6.3 , 2010 – 7.1 (Both are strong magnitude earthquakes)

P67

P68“The extent of damages caused by an earthquake is solely determined by an area’s proximity to the epicentre.”

How true is this statement? Give reasons and relevant examples in your answer

Answer in PEE format

1.Magnitude of Earthquake

2.Population density

3.Level of preparedness

4.Distance from epicentre

5.Time of occurrence

6.Type of soil

Magnitude of the EarthquakeP : The strength of an earthquake, based on the energy released from the focus.

E: The higher the magnitude of an earthquake, the higher the possibility of infrastructure collapsing, as they are unable to withstand the force exerted by the earthquake, the greater the extent of damages. This may result in the death of more people who are buried under the debris, and the country’s economy will be crippled as resources will be diverted to rebuild the country while investors lose confidence in the country.

Eg : The Great Kobe Earthquake in 1995 (7.2 on Richter Scale; lasted 20 secs, 5000 people died, 300000 people became homeless. The Great East Japan Earthquake in 2011 (8.9 on Richter Scale; 16000 deaths; tsunami with wave height up to 10m)

Population density

Point: The higher the population density of an earthquake-prone area, the higher the chances of people getting killed or injured.

Elaboration: When people are living in close proximity, the destruction of an infrastructure in an area will have an impact on a larger number of people. A stampede may also occur when so many people are trying to escape from an earthquake-prone area at the same time. All these may lead to a greater extent of damages as lives are loss when high-rise buildings topple over. Hence, a magnitude 9.0 earthquake will only cause extensive damages if the area is densely populated.

Example•Earthquake in Anchorage, Alaska in 1964•Magnitude 9.2 on the Richter Scale•Only 115 people died as the area had a small and sparse population

Level of preparednessP : Refers to how well the people know what to do in the event of an earthquake, such as having evacuation plans and trained rescue workers.

E: This will reduce the number of casualties that may arise from a stampede, and will also ensure that those who are injured receive timely medical assistance. Hence, a magnitude 9.0 earthquake may not cause extensive damages if the people know what to do and are able to evacuate safely before getting injured.

Example: In Japan, students are taught how to react when the earthquake warning signal goes off. They are to crouch under the nearest table, so as to prevent falling objects from injuring them

Distance from epicentre

P : Generally, the nearer to the epicentre, the stronger the shockwaves receive

E: The energy of the earthquake is absorbed and weakened as it radiates outwards from the epicentre to the surrounding land. Hence, a magnitude 9.0 earthquake may not cause extensive damages if the area involved is located far away from the epicentre.

Eg: During the 2011 Christchurch earthquake in New Zealand, the epicentre was in a town a few km away from the city centre. Thus, the city centre suffered more damages than areas further away from the city.

Time of occurrenceP: The time of the day during which the earthquake occurs determines where people are and what they are doing, which will affect their chances of survival.

E: If the earthquake occurs when most people are sleeping, there is a higher chance that these people will be trapped in their houses and more deaths may occur. Hence, a magnitude 9.0 earthquake may not cause extensive damages if the earthquake occurs during the day and people are more aware and thus have sufficient time to escape.

Eg: More than 2400 people died when an earthquake occurred a couple of hours after midnight in the Sun Moon Lake Region in Taiwan in 1999.

Type of soilP : Where sediments are loose and unconsolidated, the seismic waves are amplified. Structures built on saturated and unconsolidated sediments can be affected by liquefaction, where the ground becomes unstable and the saturated soil flows like a liquid

E: When sediments are loose and unconsolidated or saturated, the effects of the earthquake are amplified, which could lead to the collapse of infrastructure. Hence, a magnitude 9.0 earthquake may not cause extensive damages if the type of soil found in that area is well-consolidated and more resistant to the movements of the ground.

Eg: In the 2011 Christchurch earthquake in New Zealand, many houses and buildings had to be abandoned because of liquefaction after the earthquake.

Conclusion

The extent of damages experienced by an area is not just dependent on the magnitude of the earthquake, but also other factors as mentioned above.

These factors are interlinked and will determine how badly affected an area is.

However, men can reduce the extent of damages experienced by adopting the various adaptation measures like earthquake resistant buildings or installing earthquake monitoring and warning systems.

In December 2004, The Tsunami swamps Phuket's Chedi resort (AFP/Joanne Davis)

Tsunami

Threat of tsunamis• Tsunami refers to an usually large sea wave. • Tsunamis may be formed by:

- The movement of the sea floor during a large earthquake at subduction zones;

- An underwater volcanic eruption;- An underwater landslide; and- A landslide above sea level which causes materials to

plunge into the water.


• In 2004, a 9.2 magnitude triggered a tsunami with waves spreading throughout the Indian Ocean.

Aceh before and after the tsunami hit the area


Formation of a Tsunami

• The tsunami is formed by the movement of the sea floor during a large earthquake at the ________ zone. [1]

• The offshore earthquake forces out a ____________. [1]• On reaching shallower water, greater friction slows the waves

and forces the waves to increase in __________. [1]• At the point of impact on the coast, the tsunami waves could

reach heights of 15m. [1]

P64

• The tsunami is formed by the movement of the sea floor during a large earthquake at the subduction zone. [1]

• The offshore earthquake forces out a mass of sea water. [1]• On reaching shallower water, greater friction slows the waves

and forces the waves to increase in height. [1]• At the point of impact on the coast, the tsunami waves could

reach heights of 15m. [1]

P64

Singapore is protected to a significant degree [1] by the southern end of Malaysia Peninsula [1] and the island of Sumatra to the west [1].

The energy of waves travelling southwards would have been absorbed by the coastlines of those land masses. [1]

P64 Explain why the impact of the tsunami on Singapore was minimal.

[4]

The spread of the tsunami waves caused by the tsunami


P=Point Tsunamis can have an impact on the lives of the people.D=Describe Tsunamis are unusually large waves caused by underwater earthquakes.E=Explain Tsunamis can travel long distances and caused great destruction to coastal areas when they

sweep inland. At the point of contact on the coast, the tsunami waves could be travelling at 50km/h and may reach heights of around 15metres.

E=Example In 2004, a 9.2 magnitude earthquake occurred in the Indian Ocean and caused a tsunami with waves that spread throughout the Indian Ocean. The most damage was experienced in the low-lying coastal areas of western Sumatra, Indonesia.There was loss of lives and destruction of properties along this stretch of the coast.

P=Point Earthquakes can have an impact on the lives of the people. Earthquakes can cause fire.

D=Describe Earthquakes may rupture gas pipes and the gas can provide fuel to start fires. Earthquakes may expose electrical cables which may ignite flammable items like gas and oil.

E=Explain Once these items are ignited, fires can spread quickly to a large area, increasing the number of deaths and injured.

E=Example For example, the 1995 earthquake in Kobe, Japan. The earthquake caused extensive fires that went on for 2 days. Firemen were unable to control the fires as the ruptured water pipes meant that there was no water supply to put out the fire.

Complete Worksheet ‘The impact of a tsunami on people’s lives can be more devastating than that of an earthquake.’ How far do you agree with this statement? Give reasons for your answer. [6]

Impact of a tsunami on people’s lives (1 example)

Impact of an earthquake on people’s lives (1 example)

Healthcare

Eq and tsunamis