Moment magnitude scale

measure of earthquake size, in terms of the energy released

The moment magnitude scale is a way to measure the power of earthquakes. It is the energy of the earthquake at the moment it happens. Like the similar and older Richter scale, it is logarithmic, with a base of ten. This means that an earthquake with a magnitude of 2 is ten times stronger than an earthquake with a magnitude of 1.

Scale Number Earthquake Effect
less than 3.5 This would be a very weak earthquake. People would not feel it, but it would be recorded by geologists.
3.5-5.4 Generally felt by people, but it rarely causes damage.
5.4-6.0 Will not cause damage to well-designed buildings, but can cause damage or destroy small or poorly-designed ones.
6.1-6.9 Can be destructive in areas up to about 100 kilometers across where people live.
7.0-7.9 Considered a "major earthquake" that causes a lot of damage.
8 or greater Large and destructive earthquake that can destroy large cities.

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