Types of Earthquake
Geography: Edexcel IGCSE, topic 1.4.3
Types of Earthquakes
Earthquakes happen within the Earth at different depths. There are 2 main types of earthquakes:
What is a shallow-focus earthquake?
- Shallow-focus earthquakes are earthquakes where the focus (the point underground where the energy radiates from) is close to the Earth's surface.
- Shallow-focus earthquakes have a focus that is between 0km and 70km under the Earth's surface.
What is a deep-focus earthquake?
- Deep-focus earthquakes are earthquakes where the focus (the point underground where the energy radiates from) is far away from the Earth's surface.
- Deep-focus earthquakes have a focus that is more than 70km under the Earth's surface.
- Deep-focus earthquakes usually happen at convergent plate margins, where crust has previously been forced downwards by another plate towards the Earth's core.
- Deep-focus earthquakes are generally less damaging because the focus is so far from the Earth's surface.
What are underwater earthquakes?
- Underwater earthquakes move the bottom of the sea (the seabed).
- This can displace water and can create tsunamis (series of enormous waves).
- Waves can pick up a lot of speed in deep oceans, so tsunamis like the one that hit Japan in 2011 can catch people off-guard and cause many deaths.
Test yourself on Types of Earthquake
What are the causes of deep-focus earthquakes?
How deep is the focus of deep-focus earthquakes?
What do we call series of enormous waves caused by underwater earthquakes?