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Earthquakes and tsunamis - EdexcelCauses of earthquakes

Earthquakes are caused by the release of built-up pressure at plate boundaries. They can destroy buildings and infrastructure. Tsunamis can also occur, with equally devastating and deadly effects.

Part of GeographyWeather hazards and climate change

Causes of earthquakes

What causes earthquakes?

Earthquakes are the sudden violent shaking of the ground. This happens because the Earth's plates are constantly moving. Sometimes because of friction, plates try to move but become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released it sends out huge amounts of energy causing the Earth's surface to shake violently.

The point inside the Earth's crust where the earthquake originates from is known as the focus. The earthquake's energy is released in seismic waves, which spread out from the focus. The seismic waves are most powerful at the . The epicentre is the point on the Earth's surface directly above the focus.

The focus is the point under the earth's surface where the seismic waves start from. The epicentre is the point on the earth's surface directly above the focus.