Earthquake definition

A sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the earth's crust or volcanic action.

Causes of earthquakes

Causes of earthquakes.

The earth's crust is cracked into pieces called tectonic plates. These plates move around. In some places they move apart form each other and in other places, they move together. These movements are felt on the surface and they vary in size. Most are too small to be felt by humans and are measured using a sensitive machine called a seismometer. Some earthquakes are large and can cause extensive damage to property and loss of life. 

Effects of earthquakes

Landslides

These are just some of the effects of earthquakes. How many more can you think of?

Liquifaction

Damage to infrastructure

Homelessness

Tsunamis

Earthquake preparedness

Being prepared for earthquakes involves having a plan for before, during and after an earthquake. During an earthquake, the most important advice is to stay calm. Do you think you ill stay calm in an earthquake?

Earthquake simulators

Earthquake simulators are a great way to prepare for the unexpected. This Earthquake simulator in Honjo Bosaikan, Tokyo shows a Level Seven earthquake on the Japanese earthquake scale. 

Earthquake videos

Watching videos of earthquakes is a great way to learn about the power of earthquakes. 

               Richter Scale

The Richter scale measures the energy released

in an earthquake. The Richter scale is a logarithmic

scale with each point on the scale being ten times

larger than the point before. For example, a 5.0

earthquake is ten times larger than a 4.0 earthquake.

 

      Size                          Frequency                        Description

   < 2.0                several million a year         Microquakes - only measured by machines

2.0 - 2.9         over 1,000,000 per year         Felt by people lying down, no damage

3.0 - 3.9            over 100,000 per year         Felt by people seated, rarely causes damage, 

4.0 - 4.9       10,000 - 15,000 per year         Minimal damage, some objects move, some shaking visible

5.0 - 5.9             1000 - 1500 per year          Felt by everyone, slight damage to property

6.0 - 6.9                  100 - 150 per year         Earthquake proof buildings suffer slight to moderate damage

7.0 - 7.9                       10 - 20 per year         Damages most buildings, felt up to 250 km away from source

8.0 - 8.9                                 1 per year         Major damage to buildings, damage over extensive area

9.0 +                    1 every 10 - 50 years        Damage extends over wide area, loss of life likely

Measuring earthquakes

               Mercalli Scale

The Mercalli Scale is a descriptive scale that matches

the effects of an earthquake to a numeric level. 

 

Size     Description

   I              Not felt                         V               Moderate                        IX             Violent

  II               Weak                           VI                Strong                            X             Extreme

  III              Weak                          VII            Very strong                      XI            Extreme

  IV              Light                          VIII               Severe                           XII            Extreme