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 Felt by many indoors, few outdoors. May feel ...

A major, 7.6-magnitude earthquake struck in the Caribbean Sea on Saturday and triggered a tsunami advisory in Puerto Rico and ...

There are a number of ways to measure the magnitude of an earthquake. Most scales are based on the amplitude of seismic waves recorded on seismometers. These scales account for the distance between ...

For example, this graph shows that there are three more ... Image caption, This frequency diagram shows the magnitude of earthquakes. The vertical scale is going up in increments of 5.

Shaking categories are based on the Modified Mercalli Intensity scale. When aftershock data is available, the corresponding maps and charts include earthquakes within 100 miles and seven days of ...