Magnitude measures

The size and damaging effects or severity of an earthquake are described by measurements of both magnitude and intensity. The quantification of the size of an earthquake has been considered by seismologists for many decades. A variety of different measures have been produced to estimate and report the magnitude of a seismic event. Many attempts have been made to develop a uniform scale to measure earthquake magnitude (Kanamori, 1983) but this goal has not always been achievable due to the changes in instrumentation used over time, changes in seismic data processing techniques as well as developments in the distribution of seismic monitoring stations. As a result of these influences a variety of magnitude scales/measures have been developed and reported which have been used at various times and locations around the world. As the science of earthquakes (seismology) has developed further advances have been made in the quantification of a seismic event. In order to provide a historical continuity of the measurements made relationships needed to be developed between the various earthquake size measuring schemes. As earthquakes are the result of complex geophysical processes it is not a simple matter to find a single measure of the size of an earthquake (Kanamori, 1978).