Earthquake Notes (1)

Earthquakes Notes

What is an earthquake?

An earthquake is a sudden and violent shaking of the ground, often causing damage, loss, injury and death it usually occurs due to the movement of the earth’s crust or volcanic activity.

Where do they occur?

They occur on all forms of plate margins, constructive, destructive, collisional and conservative plate margins with different range of intensities.

     How do earthquakes form?

When plates fracture/slip they form seismic waves (vibrations) into the ground, these vibrations can be classified into to primary, secondary and surface waves.

Primary waves:

-They are the fastest moving waves

-They can pass through solids, liquids and gases easily

-These waves typically arrive at the surface as an abrupt thud.

Secondary waves:

-They move slower than primary waves,

-Can only pass through solids.

-As S waves move, they displace rock particles outward,. This results in the first period of rolling associated with earthquakes.

-They only travel through solid material, and so are stopped at the liquid layer in the Earth's core.

Surface waves:

-Move along the surface of the Earth.

-Surface waves cause the most damage. They move up and down the surface of the Earth,

 -Surface waves are the slowest moving of all waves,. So the most intense shaking usually comes at the end of an earthquake.