Describe the occurrence and distribution of earthquakes Explain how an earthquake forms Outline how earthquakes are measured Describe how a tsunami wave occurs
Describe the economic and social impacts of earthquakes in Chile and Nepal
Describe the response to these natural disasters Explain ways to reduce the damage caused by earthquakes. 3.1 Distribution of Earthquakes
An earthquake is the sudden shaking of the earth caused by the movement of the earth’s crust.
Most earthquakes occur along the edges of large plates, at destructive or conservative boundaries where they are colliding or sliding past each other (see pp. 5–6). As the plates push against each other, they create great friction . This causes energy to build up between the plates. The plates then slip at a point in the crust called the focus . Shock waves , also known as tremors or seismic waves, spread out from the epicentre , which is the point on the earth’s surface above the focus.
Seismologists are scientists who study earthquakes. They use specialised equipment to measure activity in earthquake zones. They can then use this information to predict (estimate) when and where an earthquake may occur.