Earthquakes

Question 1

What is an epicentre?

Answer 1

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

Question 2

What is a focus?

Answer 2

The point at which the earthquake occurs

Question 3

What is an earthquake?

Answer 3

• movement within the Earth’s crust causes stress to build up

• when the stress exceeds the strength of the rock, the rock fractures

• the stored energy is released as an earthquake

• intense seismic waves spread out from the focus

• these waves are what cause the ground to shake

• shallow focus = more destruction

Question 4

What are earthquakes measured using?

Answer 4

Seismograph

Question 5

What can vibrations from earth be categories as?

Answer 5

P waves or S waves

Question 6

Describe P waves

Answer 6

• primary waves
• arrive at the detector first
• are longitudinal waves - the vibrations are in the same direction as the direction of travel
• can travel through solids and liquids
• can be detected on the other side of the Earth

Question 7

Describe S waves

Answer 7

• secondary waves
• arrive at the detector second
• are transverse waves - the vibrations go at right angled to the direction of travel
• can only travel through solids
• can only be detected on the same side of the Earth as the earthquake

Question 8

Which scale is used to measure earthquakes?

Answer 8

Richter scale

Question 9

Describe the Richter scale

Answer 9

Logarithmic scale - each point is 10 times stronger that the last

For each point, approximately 30 time more energy is released

0-10 scale

Question 10

What are the primary effects of earthquakes?

Answer 10

• Ground shaking
• ground rupture

Question 11

What are the secondary effects of earthquakes?

Answer 11

• soil liquefaction
• tsunamis
• effects on people and the built environment
• landslides and avalanches
• fires

Question 12

What are the social impacts of an earthquake?

Answer 12

• Death and injury eg collapsing buildings, poorer are more vulnerable due to low cost, poorly built housing

• transport and communication links disrupted

• water pipes burst and water supplies contaminated (disease may spread)

• re-housing

• infrastructure destroyed eg roads, hindering rescue efforts

Question 13

What are the economic impacts of earthquakes?

Answer 13

• shops and businesses destroyed

• looting may take place

• damage to transport and communication links can make trade difficult

• cost of rebuilding settlement is high

• investment may be focused on only repairing damage caused by earthquake

• income could be lost

• some agricultural and industrial workers left unemployed

Question 14

What are the environmental impacts of an earthquake?

Answer 14

• the built landscape may be destroyed

• fires can spread due to gas pipe explosions

• fires can damage woodland areas

• landslides may occur

• tsunamis may cause flooding in coastal areas

• important natural and human landmarks may be lost

Question 15

What are the political impacts of an earthquake?

Answer 15

• promote intrastate conflict by increasing competition for resources

Question 16

How is an earthquake prepared for?

Answer 16

• monitoring allows for warning and evacuation

• building design (addition of shock absorbers, foundation deep in bedrock, cross bracing and light but strong buildings)

• mapping areas most at risk

• planning can ensure valuable services are not built in high risk areas

• drills and eduction

• remote sensing and GIS

Question 17

Why is earthquake preparation essential?

Answer 17

Because they are impossible to predict at the moment