Field of Science

New Zealand's earthquake

The News
Today we all woke up to the terrible news that a 6.2 magnitude earthquake hit New Zealand's second-largest city at 23:51 last night. With 65 confirmed deaths so far it's the country's worst natural disaster for 80 years.
My thoughts are with the people of New Zealand at this time.

The Science
So what exactly is a magnitude of 6.2? Due to only minor earthquakes and aftershocks hitting the UK on an average of 200 a year (That sounds like a lot actually!). The majority are minor and are not felt by humans (less than 3.5 magnitude). The last 'large' earthquake in the UK (5.6) was in February 2008 and was felt by most in the UK, but was not large enough to cause damage.  This magnitude of earthquake caused houses to shake and tremors to be felt.
Taken from http://www.maps.com/ref_map.aspx?pid=12871
 Earthquakes greater than 6.0 cause damage to buildings and the largest recorded measured 9.6 and happened in Chile in 1960. So the 6.2 earthquake was 0.6 larger than the UK earthquake back in 2008. This seems relatively small, but on the Richter scale this is a large difference. The Richter scale measures seismic energy released by the earthquake (Waves of energy released by the breaking of rocks or explosions). The scale is known as a 'base-10 logarithmic' scale, which simply means a 6.0 earthquake is 'ten times' larger than a 5.0 one. 
Therefore, the New Zealand earthquake was 'six times' larger than the 2008 UK earthquake. This explains how a large 5.6 earthquake in the UK causes less damage than the 6.2 one seen in New Zealand.


It's also not just about the magnitude, it also depends on where the epicenter (start) of the earthquake is and whether it is on a main plate boundary in the earth's crust. New Zealand is close to one of these plate boundaries, which is simply a crack in the earth's crust, and these are associated with greater earthquake or volcanic activity. The pacific plate boundary that runs next to New Zealand is also associated with high seismic activity. 
 The UK is located in the centre of one of these 'plates'  and the nearest plate boundary (the mid atlantic ridge) is approximately 900miles away. This explains why the UK's earthquakes are smaller than those in China, Chile, California, New Zealand etc.


Further Info
If you want any more information regarding earthquakes the 'British Geological Survey's website is a good place to look http: www.bgs.ac.uk
To keep up to date with the New Zealand earthquake: http://www.bbc.co.uk/news/


Thanks for reading, feedback and comments are more than welcome :)
Sam

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