What is considered a big earthquake? Earthquakes are also classified in categories ranging from minor to great, depending on their magnitude.
Class | Magnitude |
Great | 8 or more |
Major | 7 – 7.9 |
Strong | 6 – 6.9 |
Moderate | 5 – 5.9 |
Light | 4 – 4.9 |
Minor | 3 -3.9 |
Earthquake Magnitude Scale
Magnitude | Earthquake Effects | Estimated Number Each Year |
2.5 or less | Usually not felt, but can be recorded by seismograph. | 900,000 |
2.5 to 5.4 | Often felt, but only causes minor damage. | 30,000 |
5.5 to 6.0 | Slight damage to buildings and other structures. | 500 |
6.1 to 6.9 | May cause a lot of damage in very populated areas. | 100 |
7.0 to 7.9 | Major earthquake. Serious damage. | 20 |
8.0 or greater | Great earthquake. Can totally destroy communities near the epicenter. | One every 5 to 10 years |