| Strongest earthquake for 25 years wakes thousands across the UK - Feb 2008
Just before 1am on Wednesday, 27th February 2008, I woke suddenly. The bed was shaking as if someone was stood at the end of it, and was violently shaking it. Except I was alone. This was accompanied by a loud rumbling noise, however by the time I was fully awake it had stopped. I got out of bed and looked outside, but nothing seemed to be amiss, and no people were around. I decided I must have imagined it, and hopped back in to bed, just as a friend who lives 15 miles away sent me an sms asking "did the earthquake wake you?". Yes - it did!
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I popped the tv on, and Sky News were just starting to mention people calling in about earth tremors, felt in Bedfordshire, Leicestershire and Norfolk. I went to the PC and looked at the USGS Website, and sure enough the details appeared after a few minutes.
The USGS rated the earthquake as magnitude 4.7
on the Richter scale - small by worldwide
standards but significant for the UK. The epicentre was placed near the
small town of Market Rasen,
a few miles northeast of Lincoln, and some 4.2 miles underground.
Sky news continued to put callers on air listing their experiences - most
people described what I felt, vibration and loud rumbling noises. Some
folk seemed to perhaps be stretching things, referring to "cupboard
doors flying open" and "walls that looked like they were made
of paper" (I'm sure most of these people were a lot further away
from the earthquake than I was!).
After half an hour, Sky were still not giving details of the location or magnitude of the earthquake, so I mailed them the link to the USGS earthquake information page. Shortly after, they issued the information. At that point I went to bed.
| The next morning, the television was full of news on the earthquake. Thankfully there were no fatalities, although one unfortunate man suffered injuries when a chimney fell down in the earthquake. The BBC were reporting the earthquake as magnitude 5.2 - although the USGS still says 4.7 - based on information from the British Geological Survey. The BGS have also issued a PDF detailing the quake with some interesting seismograms of the time of the quake. What interested me was why the earthquake occurred - it's common knowledge that most earthquakes are triggered when pressure is suddenly released at the point where two tectonic plates slide against each other. The sudden movement results in the quake, and it's why they are common around the boundaries of the major plates. One such example is the Pacific "Ring of Fire"
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Our UK earthquake isn't located on a plate boundary however. In fact, it's nowhere near one, so how can such a large quake occur? There are actually 200 or so earthquakes in the UK each year - most are so small that they are never felt. Although the UK doesn't sit atop any major plate boundaries, the movements around the world can still affect the ground under us at weak spots. Most UK earthquakes occur around a large block of rock in the west midlands called the Midlands Microcraton. This block is over 590 million years old and there are a good deal of small but active fault lines around this area.One example of these fault lines behing behind an earthquake is the Dudley earthquake of 2002. This earthquake occurred on the 22nd September, and was magnitude 4.8, and much like the earthquake of the 27th Feb, was felt across much of the country (although not by myself!)
Market Rasen, the location of the recent quake, is not located near these faults though. Generally the Midlands Microcraton woudl affect the area west of Birmingham and the north. The last recorded earthquake of some strength in the Lincolnshire area was way back in 1755, so current theory is working along the lines that an ancient fault line has perhaps become active again. Needless to say, seismologists will be looking into this with some interest.
If you felt the quake, then the BGS are interested to hear from you - visit their website and fill in the earthquake questionnaire to help with their research!