Richter Magnitude Scale

The Richter Magnitude Scale, more commonly used by the media and the public, measures the magnitude of the earthquake. It is calculated logarithmically in which each unit of amplitude of earthquake waves is factored ten times larger than the previous reading. An earthquake measured at 8.0, for example, would be 10,000 times stronger than an earthquake measured at 4.0.

How is the Richter Magnitude of an Earthquake Arrived At?

Calculate the logarithm to base ten of the maximum seismic-wave amplitude (in 1000ths of a milimeter) recorded on a standard seismograph at a distance of 100 kilometers from the earthquake center. Got that?

Magnitude Under 2 "Micro Quake" - Recorded on local seismographs. Generally not felt.
Magnitude 3 Normally not felt.
Magnitude 4 Often felt. Damage is rare.
Magnitude 5 Felt widely. Normally only slight damage.
Magnitude 6 Poorly constructed buildings are damaged.
Magnitude 7 - 7.8 Very serious damage occurs.
Magnitude 7.8+ "Great Quake" - Tremendous destruction and loss of life.