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. read more
To be felt reasonably widely by quite a few people, an earthquake would have to be fairly shallow (less than 10km), and at least a magnitude 4. Some people still miss these. An unavoidable earthquake would be a close magnitude 5 or higher. read more
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. read more