Earthquakes in the UK

The UK is not generally associated with earthquakes, however, earthquakes do happen here. Twenty to thirty earthquakes are felt by people every year. Most of these are very small and cause no damage. However, some British earthquakes have caused some damage, although nothing like the devastation caused by large earthquakes in other parts of the world.

The largest known British earthquake occurred near the Dogger Bank in 1931, with a magnitude of 6.1. Fortunately, its epicentre was 60 miles offshore but it was still possible to cause minor damage to buildings on the east coast of England. The most damaging British earthquake was in Colchester in 1884 with a modest magnitude of 4.6. Hundreds of buildings needed repairs, chimneys collapsed and walls were cracked.

How often? - How large? A magnitude 4 earthquake happens in Britain roughly every two years. We experience a magnitude 5 roughly every 10-20 years. Research suggests that the largest possible earthquake in the UK is around 6.5.

Why? The Earth under our feet has many faults caused by our turbulent geological past. Some of these faults can be observed at the surface and mapped by geologists, others are hidden many kilometres below the surface. These faults are places where stress can build up. When stress exceeds the strength of the rocks on either side of the fault, the fault slips and an earthquake occurs. The driving forces for earthquake activity are unclear, however they may include the following. Regional compression caused by motion of the Earth’s tectonic plates. Uplift resulting from the melting of the ice sheets that covered many parts of the Britain thousands of years ago. A component of uplift may also be caused by anomalous “hot” material at the base of the crust on the western flank of mainland Britain.

Earthquakes in the UK The UK is not generally associated with earthquakes, however, earthquakes do happen here. Twenty to thirty earthquakes are felt by people every year. Most of these are very small and cause no damage. However, some British earthquakes have caused some damage, although nothing like the devastation caused by large earthquakes in other parts of the world. The largest known British earthquake occurred near the Dogger Bank in 1931, with a magnitude of 6.1. Fortunately, its epicentre was 60 miles offshore but it was still possible to cause minor damage to buildings on the east coast of England. The most damaging British earthquake was in Colchester in 1884 with a modest magnitude of 4.6. Hundreds of buildings needed repairs, chimneys collapsed and walls were cracked. How often? - How large? A magnitude 4 earthquake happens in Britain roughly every two years. We experience a magnitude 5 roughly every 10-20 years. Research suggests that the largest possible earthquake in the UK is around 6.5.

Significant UK earthquakes (red, 1970-present and historical yellow, pre-1970). Move pointer over an event for more information
Where? The spatial distribution of British earthquakes shows strong regional variation. Most earthquakes occur on the western side of the British mainland. Earthquakes are almost completely absent from eastern Scotland and north east England. Similarly, Ireland is almost completely free of earthquakes. The North Sea is more active than the mainland.

Figure 2. Instrumental seismicity (red, 1970-present) for earthquakes with ML >2.0 and historical seismicity (yellow, pre-1970) for earthquakes with ML >3.0 (click here to view as larger image).
Why? The Earth under our feet has many faults caused by our turbulent geological past. Some of these faults can be observed at the surface and mapped by geologists, others are hidden many kilometres below the surface. These faults are places where stress can build up. When stress exceeds the strength of the rocks on either side of the fault, the fault slips and an earthquake occurs. The driving forces for earthquake activity are unclear, however they may include the following. Regional compression caused by motion of the Earth’s tectonic plates. Uplift resulting from the melting of the ice sheets that covered many parts of the Britain thousands of years ago. A component of uplift may also be caused by anomalous “hot” material at the base of the crust on the western flank of mainland Britain.

Figure 3. Geological fault map of the UK (click here to view as larger image).