Why and where do earthquakes occur?

World Seismicity

If we look at the pattern of where earthquakes occur around the world, it is clear that most of the earthquake activity is concentrated in a number of distinct earthquake belts.

For instance, there are many earthquakes recorded around the edge of the Pacific Ocean, or in the middle of the Atlantic Ocean.

These earthquake belts provide an important clue in the development of the theory of plate tectonics.

Movement of tectonic (or lithospheric) plates

The outer shell of the Earth, or crust (continental and oceanic) and the upper part of the mantle, is made up of a number of rigid segments called tectonic plates. These plates are continually moving at rates of a few centimetres per year (about as fast as your fingernails grow), driven by forces deep within the Earth.

Below the tectonic plates, lies the Earth’s asthenosphere. The asthenosphere behaves like a fluid over very long time scales. There are a number of competing theories that attempt to explain what drives the movement of tectonic plates.

At the boundaries between the plates, where they are moving together, apart or past each other, tremendous stresses build up, and are where most earthquakes occur.

Plate tectonic map of the world showing direction of movement

Plate tectonics Juan plate Phillipine plate North American plate North American plate Caribbean plate Arabian plate Eurasian plate Australian plate African plate South American plate Cocos plate Antarctic plate Indian plate Pacific plate Pacific plate Scotia plate Pacific plate Nazca plate

Related topics

Elastic rebound Elastic rebound theory

The process of ground being subjected to a growing force until it snaps or breaks is explained in a theory called the elastic rebound theory.

Divergent boundary Plate tectonics

Tectonic plates can move relative to each in different ways. This movement gives rise to different types of plate boundaries with different properties and characteristic earthquakes.

Core structure The structure of the Earth

Studying the signals from distant earthquakes has allowed scientists to determine the internal structure of the earth.

Driving tectonic plates What drives the movement of tectonic plates?

There are a number of competing theories that attempt to explain what drives the movement of tectonic plates.

Classroom activities | External links

Earth Learning Idea Geobattleships | Earth Learning Idea

Do earthquakes and volcanoes coincide?

What drives the plates? What drives the plates? | Earth Learning Idea

Using pupils to act as the lithosphere, this activity explains the competing theories of what forces drive the movement of tectonic plates.

Earth Learning Idea Plate tectonics through the window | Earth Learning Idea

If you were at a plate tectonic margin that was very active, what might you see? What might you hear? What might you sense? What might you feel?