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The History of Earthquake Magnitude Scales

Almost everyone has heard of the Richter Scale, but few are familiar with its invention in the mid -1930s or its limitations. Over the next few decades, at least seven other magnitude scales were developed by seismologists. Ideally, the magnitude of an earthquake should be independent of the method (scale) used to measure it, but in practice this is not the case. All magnitude numbers are proxies for the energy released at the earthquake source. The scale most widely used today, and the one most closely tied to actual energy, is the moment magnitude scale, first proposed in 1972. As originally defined, moment magnitude could be calculated only for relatively large earthquakes. Recently, however, a method has been developed for extending the moment magnitude scale to events with magnitudes less than 4.

Dr. Charles K. Scharnberger

Professor Emeritus of Earth Sciences, Millersville University

Wednesday, November 12, 2014

4 - 5 pm

Roddy Hall, Room 149

Refreshments will be available at 3:30

All are invited to attend!!!