In ancient times earthquakes were thought to be caused by restless gods or giant creatures slumbering beneath the Earth.
In Greek mythology, Poseidon is the god of the sea and is usually depicted carrying a trident. One of Poseidon's 'nicknames' is Earthshaker. Stories are told of Poseidon striking the ground with this trident, which triggered earthquakes.
In contrast, the early Greek philosophers developed a theory that earthquakes were caused by movements of gases trying to escape from underground.
Up until the 18th century western scientists, including Isaac Newton, thought they were caused by explosions of flammable material deep underground.
In 1760, the Reverend John Mitchell proposed that earthquakes were caused by rock movements and related the shaking to the propagation of elastic waves within the earth.
Was the Reverend Mitchell correct? What causes earthquakes?
In the Pacific North West, traditional stories speak of shaking and flooding from the sea by referring to a struggle between a large bird, the Thunderbird, and a whale. Do you think this could have been a tsunami generated by an earthquake?
In Greek mythology, Poseidon was the god of the sea and was usually depicted carrying a trident or fish spear. One of his nicknames is Earthshaker. With his trident he could strike the ground, causing earthquakes.
In Japan, earthquakes were thought to be caused by a monster catfish (Namazu) that lived under Japan. In this picture people are punishing the catfish for causing a large earthquake in 1855.
The great Lisbon earthquake in Portugal and the subsequent tsunami of 1755 caused massive destruction and had a huge effect on European scientific and philosophical development.
Some 60 000 people were killed, either by collapsing buildings or in the tsunami waves.
Up until this time, there had been a general religious belief that God would not allow such a calamity. The Lisbon quake triggered the thinkers of the time to try and explain earthquakes in a non-religious context. Hence this event probably triggered the birth of modern earthquake science.
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.
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.
Studying the signals from distant earthquakes has allowed scientists to determine the internal structure of the earth.
Earthquakes do not occur randomly on the Earth. The pattern of earthquake locations can be explained by assuming the Earth's surface is made up from rigid plates that are in motion relative to each other.
There are a number of competing theories that attempt to explain what drives the movement of tectonic plates.