Magnitude measures the energy released at the source of the earthquake. Magnitude is determined from measurements on seismographs. Intensity measures the strength of shaking produced by the earthquake at a certain location.
Intensity is determined from effects on people, human structures, and the natural environment.
The following table gives intensities that are typically observed at locations near the epicenter of earthquakes of different magnitudes. Not felt except by a very few under especially favorable conditions. Felt only by a few persons at rest, especially on upper floors of buildings. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake.