Earthquakes

Focus - the place where earthquakes begin,                               deep within the earth's crust.

Epicentre - the point above the focus where the earthquake    is most strongly felt.

Shock waves - waves from the earthquake that radiate             from the epicentre.

Primary waves - weak waves that cause the surface to move in the direction of the wave movement.

Secondary waves - stronger waves that warn of worse to         come.

The richter scale - measures the magnitude (strength) of earthquakes. (1-10)

The Mercalli scale - measures the shaking and damage (intensity). (1-12).

Ground shaking - The longer the shaking the more damage is caused.

Landslides - slopes are weakened by strong shaking and give way.

Tsunamis - result when earthquakes occur under the sea.

Liquefaction - Groundwater rises to the surface, turning soft ground to mud.