What is considered a big earthquake? Earthquakes are also classified in categories ranging from minor to great, depending on their magnitude.

ClassMagnitude
Great8 or more
Major7 – 7.9
Strong6 – 6.9
Moderate5 – 5.9
Light4 – 4.9
Minor3 -3.9

Earthquake Magnitude Scale

MagnitudeEarthquake EffectsEstimated Number
Each Year
2.5 or lessUsually not felt, but can be recorded by seismograph.900,000
2.5 to 5.4Often felt, but only causes minor damage.30,000
5.5 to 6.0Slight damage to buildings and other structures.500
6.1 to 6.9May cause a lot of damage in very populated areas.100
7.0 to 7.9Major earthquake. Serious damage.20
8.0 or greaterGreat earthquake. Can totally destroy communities near the epicenter.One every 5 to 10 years
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