There are various scales used to measure the size of earthquakes. Many people are familiar with the Richter Scale, which describes the amount of energy released at the source deep underground. Earth scientists now refer to this as the local magnitude (ML). When people talk about a magnitude 2 event, this is what they mean.

The magnitude scale is logarithmic, which means that each increase of 1 in the scale means a 10-fold increase in the amount of energy released. So, a magnitude 2 event is ten times bigger than a magnitude 1, and a magnitude 3 is ten times bigger than a magnitude 2, and so on.

Destructive earthquakes generally have magnitudes of 6 or above. The 2011 earthquake in Japan had a magnitude of about 9; ten million times stronger than a magnitude 2 event.