Earthquakes are caused by movements of rock deep within the Earth's crust. This movement releases seismic energy in the form of waves. The location where the rock movement originates is called the focus, and the area directly above on the surface is called the epicenter. Earthquakes are measured on both the Richter scale, which measures the amount of energy released, and the Mercalli scale, which measures the impact on humans. A 2011 earthquake in Christchurch, New Zealand registered a 6.3 on the Richter scale and a 10 on the Mercalli scale, causing significant devastation.

1. Earthquakes

2. What is an Earthquake?
• Earthquakes are caused by the movement of
rock deep within the Earth’s crust.

3. Energy is Released
• Sudden movements that release significant amounts of
energy in the form of primary and secondary seismic
waves.

4. Focus and Epicentre
• The place where the rock movement occurs is
called the focus.
• The place directly above on the Earth’s surface is
called the epicentre.

5. Measuring Earthquakes

6. Richter Scale
• Measures the amount of energy released from
the earthquake (magnitude) over 6 is considered
a major EQ

7. Mercalli Scale
• measures the impact on humans (1-12)
• Devastation after Earthquake in Haiti 2010

8. Christchurch
• Chistchurch Earthquake 22, Feb 2011
• Magnitude 6.3
• Mercalli 10
• http://www.christchurchquakemap.co.nz/
• http://www.youtube.com/watch?v=BfcWraeZvcw

9. Over to you
Use your and the textbook (p97-98) to answer the following
Questions.
• 1. What types of earthquakes occur in Australia?
• 2. Outline some of the impacts of earthquakes.
• 3. a) What factors would affect the rating an earthquake receives on
the Mercalli Scale ? (e.g the location of the epicentre)
b) Outline what can be done to minimise these effects.
• 4. Complete “Applying and Analysing” Question 1 on page 101