Magnitude and Energy of Earthquakes

Lists and cataloguers of earthquakes are frequently used for both popular and scientific purposes. Occasionally such lists are compiled without suitable discrimination including all the shocks, small and large, which may happen to come to notice. Under such circumstances the number of earthquakes listed for any given region is likely to be a better index of the density of population than of the seismicity; for minor shocks are very frequent in all seismic regions, and even in many districts not commonly thought of as seismically active. Similar undiscriminating use of instrumental data gives undue weight to minor shocks occurring near seismological stations.