Earthquakes

Question 1

What is the

Richter Scale?

Answer 1

A numerical scale used to measure the magnitude of an earthquake.

Question 2

What is a

seismograph?

Answer 2

An instrument used to measure the seismic waves caused by earthquakes and other things that shake the earth.

Question 3

What is the

epicentre?

Answer 3

The epicentre is the point on the ground surface directly above the focus.

Question 4

What is the

focus?

Answer 4

The focus is the point under the surface where the earthquake originates.

Question 5

What is the

crust?

Answer 5

Crust: A thin outer layer of the earth

Question 6

What causes plates to move?

Answer 6

Convection current in the magma moves the plates around.

The movement of magma in the mantle heated from the core. As it rises towards the crust it cools and moves back towards the core.

Question 7

What are the:

three P’s

Answer 7

• Predict
• Protect
• Prepare

Question 8

Explain the following when talking about the 3 P’s:

predict

Answer 8

• Accurate prediction is very difficult.
• 95% of all earthquakes occur close to plate boundaries.
• precursors:
  
  • Most likely to occur after long periods without any plate movement. (seismic gap)
  • Small cracks can develop in rocks. This can cause the ground to become deformed and change shape
    * Radon gas can be released.
    * Water levels can decrease in wells.
  • Small earthquakes can be detected called foreshocks.
  • Strange animal behaviour: snakes crawl out of holes in the ground, dogs bark uncontrollably.

Question 9

Explain the following when talking about the 3 P’s:

protect

Answer 9

• Over 10,000 deaths a year are caused by earthquakes.
  
  • Most of these deaths are caused by damage to property and buildings collapsing.
• By designing buildings better and making structures safer we can provide protection.
  
  • Older buildings and bridges can be ‘retro-fitted’. This is strenghining them to make them more earthquake proof.

Question 10

Explain the following when talking about the 3 P’s:

prepare

Answer 10

• Good preparation can limit worst effects of an earthquake.
  
  • It should involve the local authorities and emergency services as well as people living in the area.
• Most places at risk from earthquakes have an emergency disaster plan. It has three parts;
  
  • what to do before the event,
  • second to try to save lives and look after the worst affected,
  • finally bring the area back to normal as quickly as possible.
• Good preparation can include regular practise
• In some countries, local people are educated as to what to do: here are some examples:
  
  • Turn off gas
  • Get under a table
  • Have an emergency kit containing:
    * bottled water
    * tinned food
    * battery powered radio and torch

Question 11

What was world’s largest earthquake?

Name, size and location

Answer 11

• Name: The Indian Ocean earthquake of 2004
• Size: 9.1
• Location: where the Eurasian plate meets the Indian plate