Earthquake Richter Scale - What is Richter Magnitude?
Seismologists use a Magnitude scale to express the seismic energy released by each earthquake. Here are the typical effects of earthquakes in various magnitude ranges:
- < 3.5 Generally not felt, but recorded.
- 3.5-5.4 Often felt, but rarely causes damage.
- Under 6.0 At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings over small regions.
- 6.1-6.9 Can be destructive in areas up to about 100 kilometers across where people live.
- 7.0-7.9 Major earthquake. Can cause serious damage over larger areas.
- 8 or greater Great earthquake. Can cause serious damage in areas several hundred kilometers across.
The magnitude of most earthquakes is measured on the Richter scale, invented by Charles F. Richter in 1934. The Richter magnitude is calculated from the amplitude of the largest seismic wave recorded for the earthquake, no matter what type of wave was the strongest. The Richter magnitude scale, more correctly local magnitude ML scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a Wood–Anderson torsion seismometer output.
Using this scale, a magnitude 5 earthquake would result in ten times the level of ground shaking as a magnitude 4 earthquake (& 32 times as much energy would be released).
(wikipedia.org, seismo.unr.edu, geo.mtu.edu)
