What is mean by earthquake magnitude?
The Richter magnitude scale, also known as the local magnitude (ML) scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a Wood–Anderson torsion seismometer output. So, for example, an earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10 times larger than one that measures 4.0. The effective limit of measurement for local magnitude ML is about 6.8. Though still widely used, the Richter scale has been superseded by the moment magnitude scale, which gives generally similar values. The energy release of an earthquake, which closely correlates to its destructive power, scales with the 3⁄2 power of the shaking amplitude. Thus, a difference in magnitude of 1.0 is equivalent to a factor of 31.6 ( = (101.0)(3 / 2)) in the energy released; a difference of magnitude of 2.0 is equ
Magnitude : A value related to the amount of energy released during an earthquake, calculated on the basis of data obtained from measuring instruments. To compare earthquakes, we must obtain a fundamental value for an earthquake which is independent of damage caused and of the point of observation. The magnitude of an earthquake, a concept introduced in 1935 by the American Richter, enables the energy released during an earthquake to be estimated on the basis of data obtained from seismograms. Since then, it has been called the Richter scale. Sources: http://www.cite-sciences.fr/lexique/definition1.php?
