Earthquakes (ch.4)

Question 1

Seismology

Answer 1

The scientific study of earthquakes

Question 2

Magnitude

Answer 2

The strength of an earthquake

Question 3

Earthquake

Answer 3

a series of seismic waves or tremors in the earth’s crust

Question 4

What causes earthquakes?

Answer 4

Earthquakes are caused when pressure builds up at the edge of the plates as they collide or slide past one another. When this pressure is released a huge amount of energy is released causing the plates to shake. This shaking movement is the earthquake.

Question 5

Fault lines

Answer 5

long deep cracks in the earth’s crust

Question 6

Focus

Answer 6

The point where an earthquake begins deep underground

Question 7

Epicentre

Answer 7

The point on the Earth’s surface directly above the focus

Question 8

Tremors

Answer 8

Waves of seismic energy which spread out from the focus

Question 9

Aftershocks

Answer 9

Smaller tremors which may occur hours or days after the original earthquake. They can be extremely dangerous as they may cause already damged buildings to collapse.

Question 10

Name a fault line

Answer 10

San Andreas Fault, California, USA

- boundary between the Pacific and American plates

Question 11

Seismograph

Answer 11

an instrument used to measure the strength or force of an earthquake

Question 12

Richter Scale

Answer 12

registers the scale or magnitude of an earthquake.

Question 13

How does the Richter Scale work?

Answer 13

The scale ranges from 1 to 10, 1 is the weakest and 10 is the strongest. An increase of one unit on the scales means that an earthquake is 10 times more powerful.

Question 14

Name three major earthquakes

Answer 14

1. Chile - 1960 9.5 magnitude
2. Alaska - 1964 9.2 magnitude
3. Sumatra - 2004 9.1 magnitude

Question 15

Explain how a tsunami occurs and include an example.

Answer 15

A tsunami occurs when an earthquake happens under the ocean.

1. As the plates move vertically, a huge volume of water is displaced.
2. Energy from the earthquake travels through the sea water and creates waves.
3. The waves reach the shallow water near the coast and can grow to height as high as 30m.
4. The water floods the coastline - huge damage is done to property and the environment and many lives can be lost.

e. g. Japanese Tsunami 2011
- killed 16,000 people

Question 16

Explain three ways earthquakes can be predicted

Answer 16

1. Monitoring ground movement by placing laser beams across a fault.
2. Monitoring the level of Radon gas in an area around a fault. Gas level can rise before an earthquake.
3. Watching animal behaviour. Some animals and birds can sense that an earthquake is about to occur.

Question 17

How can the damage of earthquakes be reduced?

Answer 17

1. Preventing the construction of buildings on top of known fault lines.
2. Buildings can be built with braces on their corners to limit the effects of shaking. Some buildings in Japan and Mexico have had shock absorbers added to their foundations to dampen the effect of shaking.
3. Having regular earthquake drills so that people know what to do if an earthquake occurs. In Japan, schoolchildren practice ‘duck, cover and hold’ routines in which, if an earthquake happens, they duck under their table. This offers some protection if the building collapses.

Question 18

Outline the effects of an earthquake in a developed country.

Answer 18

Japan
Annual national income: $4.9 trillion (2016)
Date: 16 April 2016
Epicentre: Below Kumamoto City, in the Kyushu region of Japan
Tectonic plates: Pacific Plate and Philippine Plate collide with the Eurasian Plate
Magnitude: 7.2
Social impact: 32 died, 1,000 were injured, 90,000 had to leave their homes
Economic impact: bridges and tunnels collapsed, landslides covered roads, 200,000 homes without electricity

Question 19

In reference to a case study you have done, outline the effects of an earthquake in a developing country.

Answer 19

Haiti

• located on an Island in the Caribbean
• 2010 pop. = 10 million
• poorest country in the western hemisphere

-On 12 Jan. 2010 a 7.0 magnitude earthquake hit Port-au-Prince, Haiti. It was one of the most devastating earthquakes ever recorded in history. Much of Port-au-Prince was reduced to rubble.

Social Impact
-poorly constructed houses collapsed
= 230,000 died instantly; 1 million left homeless.
In total, the earthquake affected 3 million people.

• All of Haiti’s hospitals damaged or destroyed.
• Water, electricity and sewerage infrastructure was damaged
• Poor sanitation conditions led to outbreaks of cholera.

Aid agencies rushed to helped - delayed because the seaport and airport had been destroyed.

Economic Impact

• Key transport and telecommunication systems, including the seaport and airport, were destroyed.
• Government and public buildings, such as the National Palace, Palace of Justice and National Assembly, were destroyed.
• 250,000 houses and 30,000 commercial buildings were damaged and had to be demolished.

In the aftermath of the earthquake, it was clear that aid would be needed not just for one month, but for many years. The economic development of the country became vital so that people would be better able to manage another disaster in the future.

Question 20

How would the response to an earthquake change in a developed and a developing country?

Answer 20

1. Developed countries have more resources and are more equipped to deal with the aftermath of an earthquake.
2. Developed countries have access to better technologies which can help predict when an earthquake will occur.
3. Governments have more jurisdiction to prevent the construction of buildings in areas prone to earthquakes.