RICHTER SCALE

DescriptorRichter Magnitudes Earthquake Effects Average Annually
MicroLess than 2.0 Microearthquakes, not felt. About 8,000 per day
Very minor2.0-2.9 Generally not felt, but recorded. About 1,000 per day
Minor3.0-3.9 Often felt, but rarely causes damage. 49,000 (estimated)
Light4.0-4.9 Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 6,200 (estimated)
Moderate5.0-5.9 Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. 800
Strong6.0-6.9 Can be destructive in areas up to about 100 miles across in populated areas. 120
Major7.0-7.9 Can cause serious damage over larger areas. 18
Great8.0 or greater Can cause serious damage in areas several hundred miles across. 1

(Adapted from U.S. Geological Survey documents.)

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