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2008 Lincolnshire earthquake

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The 2008 Lincolnshire Earthquake struck the United Kingdom on 27 February 2008. According to the British Geological Survey, the quake, which occurred at 00:56:47.8s GMT, registered a reading of 5.2 on the Richter scale and was centred about 2.5 miles (4 km) north of Market Rasen. The duration of the earthquake has been confirmed as roughly 10 seconds long. The focus has been estimated at a depth of around 18 km, typical of the majority of earthquakes.

The duration of the 'quake was actually a little over two minutes, per seismograms recorded on the British Geological Survey's seismograph network. It is probable that most people slept through the primary and secondary ground waves, and subsequent Love waves, and were woken by the later Rayleigh waves. The latter waves produce the largest ground movements and are used to calculate the Richter magnitude.

The tremors were felt across a wide area of England and Wales, from Hampshire in the south, to Newcastle upon Tyne in the north, Wiltshire in the south west and as far west as Bangor, Northern Ireland, with the effects being strongest around the epicentre in Lincolnshire. Structural damage has been recorded in some areas, including two cases where chimneys have collapsed and injured residents. The first aftershock was recorded less than two hours after the initial quake at a magnitude of 1.8.

The tremor is the largest earthquake to affect the UK since the 1984 Lleyn Peninsula earthquake, which measured 5.4.

Location

The British Geological Survey stated that the epicentre of the earthquake was north of Market Rasen and south-west of Grimsby, at 53.321°N, 0.314°W. A preliminary report from the BGS stated that the earthquake occurred at a depth of , although this was later updated to .

Cause

The 2008 Lincolnshire earthquake was caused by the sudden rupture and motion along a strike-slip fault, beneath Lincolnshire. Earthquake motion occurred over a time span of ~2 minutes but it was most intense and was felt at the surface for just 10 to 30 seconds; maximum vertical ground motion at the epicentre of the earthquake was only ~1 mm. Computer calculations carried out by the BGS infer sinistral motion on a N-S or dextral motion on a E-W orientated strike-slip fault. The two aftershocks (1.8 & 2.2 ML Richter Scale) thus far observed, ~ SSW of the main earthquake event, point to an approx. N-S orientated fault. From the 5.2 ML magnitude of the main earthquake, a motion of a few centimetres along a ~ long fault rupture is derived. The energy released was 3.98×1012 joules (equal to the detonation of ~950 tonnes of TNT).

Unlike typical earthquakes worldwide, the earthquakes of Northern Europe are intraplate earthquakes, meaning they are not close to tectonic plate boundaries. Most intraplate earthquakes in Northern Europe (and the UK) are thought to be driven by distant tectonic stresses - a combination of E-W North Atlantic Ridge and N-S African Plate regional stress fields, and local mantle conditions. Indeed, the motion on the strike-slip fault responsible for 2008 Lincolnshire earthquake is compatible with a local NW-SE stress field; a product of the E-W and N-S regional stress fields.

Only a minority of earthquakes in the UK are related to post-glacial rebound e.g. the minor earthquakes (<3.5 ML) of western Scotland, where glaciers ~1 km thick existed during the peak of the last Ice Age.

Impact

The earthquake resulted in structural damage to many homes and businesses in the epicentral area. Buildings as large as apartment blocks were reported to have shaken for up to 30 seconds afterwards. Birds and pets became highly agitated. There were no deaths, but a 19 year old man in Wombwell, South Yorkshire suffered a broken pelvis when a piece of chimney fell onto his attic bed, The earthquake was felt by people as far south as Hampshire, where the earthquake was felt as a mild but noticeable vibration, and as far away as Bangor, Northern Ireland where it woke sleeping people. Police in the Midlands received more than 5,000 telephone calls in an hour from members of the public regarding the earthquake. The earthquake caused power cuts in some areas.

Magnitude

The British Geological Survey gave the earthquake a preliminary reading of 5.2 on the Richter scale, while the United States Geological Survey reported it measured 4.7 on the Richter scale based on initial measurements. The French Atomic Energy Commission estimated the magnitude was 5.4 on the Richter scale.

Aftershocks

An aftershock measuring 1.8 on the Richter scale was recorded by the BGS at 02:46:06.4 GMT.

Significance

It was the largest earthquake in the UK since the 1984 Lleyn Peninsula earthquake, which was magnitude 5.4. The BGS described the earthquake as an "extremely large earthquake in UK terms but not large in world terms". Approximately 200 earthquakes occur in the UK every year, approximately 175 of which are small enough not to be noticed by humans.

See also

References

External links



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Last updated on Wednesday March 12, 2008 at 10:28:24 PDT (GMT -0700)
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