In this section:
- What is an earthquake?
- BGS earthquake monitoring
- How are earthquakes detected?
- What causes earthquakes?
- Where do earthquakes occur?
- How do earthquakes affect people?
What is an earthquake?
Earthquakes are among the most deadly natural hazards. There are around 100 earthquakes each year of a size that could cause serious damage. They strike without warning and many of the Earth’s earthquake zones coincide with areas of high population density. When large earthquakes occur in such areas the results can be catastrophic, with terrible loss of human lives and untold economic cost.
An earthquake is the sudden release of strain energy in the Earth’s crust resulting in waves of shaking that radiate outwards from the earthquake source. When stresses in the crust exceed the strength of the rock, it breaks along lines of weakness, either a pre-existing or new fault plane. The point where an earthquake starts is termed the focus or hypocentre and may be many kilometres deep within the earth. The point at the surface directly above the focus is called the earthquake epicentre.
Intense vibrations, or seismic waves, spread out from the initial point of rupture, the focus, like ripples on a pond. These waves are what makes the ground shake and can travel large distances in all directions. Near the focus, the waves can be very large, making them extremely destructive.
BGS earthquake monitoring
The BGS Earthquake Seismology Team is the UK’s national earthquake monitoring agency. We operate a network of sensors across the UK to measure earthquakes in the British Isles and around the world. We use the data we collect to investigate the nature and distribution of earthquake activity, and what makes them happen, to improve our understanding of earthquake hazards.