How are earthquakes measured?
As when the to plates move against each other and the stress builds up in the hypo centre. Then energy is released from the hypo centre which emits into the earth in waves called the seismic waves.The energy released can be measured in different ways such as the Richter scale. What is the Richter scale? It gives the energy of an earthquake a numerical value for how strong it is used to measure the power of earthquakes. The Earthquakes that have recorded at less than about 2.0 on the Richter scale they are nothing to worry about because they can be hardly felt, when scale hits more than 5.0 that is where most people can feel the shake. The other scale for measuring the earthquakes is Mercalli scale this scale measures the intensity of the earthquake. The following tells us this is measured. The lower numbers are quakes that on people felt but the higher numbers are quakes that did structural damage. The image on the side shows us the comparison between the Richter scale and the Mercalli scale
Source:
http://www.dnr.mo.gov/geology/geosrv/geores/richt_mercali_relation.htm
http://www.christchurchquakemap.co.nz/
Source:
http://www.dnr.mo.gov/geology/geosrv/geores/richt_mercali_relation.htm
http://www.christchurchquakemap.co.nz/
After recalling to the chart the Christchurch 22nd February earthquake was to be 6.3 and this quake was also said to IX which is violent on this chart. The graph below shows us about the magnitudes of all of the earthquake till know including the February 2011 one.