Magnitude of Earthquakes

1. Tectonic processes of earthquakes

a) stress builds up and exceeds strength of the fault

b) sudden release of seismic waves, radiating energy from the focus

2. Magnitude of earthquakes

a) affected by amount of energy released through ground movement

b) recorded using seismometers

3. Measuring earthquakes

a) Richter Scale measures local magnitude of earthquakes

b) Moment Magnitude Scale measures larger earthquakes more reliably

What is the relationship between the earthquakes and plate boundaries?

Plates are the broken pieces of the earth's crust.

Earthquakes occur when there is plate movement along plate boundaries. The plate movements cause the slow build-up of stress on the rocks found on either side of the fault. When the rock can no longer withstand the increasing stress, they can suddenly slip many metres, causing an earthquake.

What is the difference between focus and epicentre?

The focus is the point which the earthquake originates. The point on the earth’s surface directly above the focus is the epicenter.

What is an aftershock?

After an earthquake event, the stress from the ground within the earth’s crust may cause many smaller earthquakes called aftershocks to occur along the fault line

Read about how earthquakes are formed @ http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/earthquakes_rev1.shtml

Watch the video on the 10 deadliest Earthquake and find out more about the impacts of some of the deadliest earthquake in history, including the one that hit Haiti in 2010, causing more than 220,000 people to be killed and more than 3 million to be affected.

Each circle represents one earthquake, with its size proportional to its magnitude and the color indicating the depth of the earthquake.

What cause earthquakes?

Why are earthquakes of greater magnitude with shallower depths?

Where are earthquakes mainly found?

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