Natural Disasters, June 23

1946    Vancouver Island Earthquake, struck Vancouver Island in British Columbia.

2001    An 8.4 Mw earthquake struck southern Peru with a maximum Mercalli Intensity of VIII, Severe. A destructive tsunami followed killing at least 74 people and injuring 2,687.

            Earthquakes are measured today using the Modified Mercalli Intensity scale. This scale measures the effects of an earthquake, rather than the moment magnitude. Mw would be the measure of the moment magnitude. The Mercalli scale is a revised version of the Rossi-Forel scale and has gone through a number of changes since first developed in 1884. Although there are twelve degrees defining the Modified Mercalli scale, we usually only see the most severe which are X, XI, and XII. The scale uses Roman Numerals and starts with I which is not felt except by a few. A good way to remember it is remember V, that is a moderate earthquake and is felt by nearly everyone around it. VI – VII are strong. VIII is severe and IX is violent, but the ones you usually see reported are X-XII, these are Extreme and are the ones with large amounts of destruction.


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