I Felt by very few people; barely noticeable. II Felt by a few people, especially on upper floors. III Noticeable indoors, especially on upper floors, but may not be recognized as an earthquake. IV ...

Earthquakes and seismic activity often happen with sudden movements underground with tectonic plates. Seismographs are used by scientists to measure the time, location and strength of an earthquake.

I Felt by very few people; barely noticeable. II Felt by a few people, especially on upper floors. III Noticeable indoors, especially on upper floors, but may not be recognized as an earthquake. IV ...