Modified Mercalli Intensity vs. Richter Magnitude

Earthquakes are commonly measured in one of two ways. (1) The Modified Mercalli Intensity scale, in Roman numerals, measures the event in terms of how people and structures react to it. (2) Richter Magnitude, in Arabic numerals, is a measure of the energy released by the earthquake. They can be compared as shown below:

Modified Mercalli
Intensity Scale
Richter Magnitude Earthquake effects
I, II Less than 3.5 Generally not felt, but recorded.
III-IV 3.5-5.4 Often felt, but rarely causes damage.
V-VII Under 6.0 At most slight damage to well-
designed buildings. Can cause major damage to poorly constructed buildings over small regions.
VIII-IX 6.1-6.9 Can be destructive in areas up to about 100
kilometers across
X-XI 7.0-7.9 Major earthquake. Can cause serious damage
over larger areas. Most buildings destroyed
XII 8 or greater Great earthquake. Can cause serious damage in
areas several hundred kilometers across
     

 

 


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