Magnitude 12
Magnitude 12 : A numerical quantity, devised by the late American Professor, Charles F. Richter, in the 1930's and denoted by Arabic integers with one decimal place accuracy (for example 7.8) to characterize earthquakes in terms of the total energy released after adjusting for difference in epicentral distance and focal depth. Magnitude differs from intensity in that magnitude is determined on the basis of instrumental records; whereas, intensity is determined on the basis of subjective observations of the damage. Measured on a logarithmic scale, magnitude is open ended theoretically, with the two largest magnitude earthquakes to date being the M 9.5 Chile earthquake of 1960 and the M 9.2 Alaska earthquake of 1964. Moderate-magnitude earthquakes have magnitudes of 5.5 to 6.9; largemagnitude earthquakes have magnitudes of 7.0 to7.9; and great-magnitude earthquakes have magnitudes of 8.0 and greater. The energy increases exponentially with magnitude. For example, a magnitude 6.0 earthquake releases 31.5 times more energy than a magnitude 5.0 earthquake, but (31.5) (31.5) or approximately 1, 000 times more energy than a magnitude 4.0 earthquake
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