The Modified Mercalli Intensity Scale
Various scales for measuring the degree of earthquake disturbance have been designed by various people and agencies over the centuries of human civilisation. The scale in most general use at present is called the Modified Mercalli Scale, and has a maximum intensity rating of 12. Maps relating the felt intensity effects of earthquakes are called Isoseismal maps, and contour regions having the same value on the Modified Mercalli Scale. This scale is summarised below
MM I Not felt by humans, except in especially favourable circumstances, but birds and animals may be disturbed. Reported mainly from the upper floors of buildings more than 10 storys high. etc MM II Felt by a few persons at rest indoors MM III Felt indoors, but not identified as an earthquake by everyone. MM IV Generally noticed indoors, but not outside MM V Generally felt outside, and by almost everyone indoors. Most sleepers awakened. A few people frightened MM VI Felt by all. People and animals alarmed. Many run outside. Difficulty experienced in walking steadily MM VII General alarm. Difficulty experienced in standing. Noticed by drivers of motor cars. Trees and bushes strongly shaken. MM VIII Alarm may approach panic. Steering of moror cars affected MM IX General panic MM X Most masonry structures destroyed MM XI Wooden frame structures destroyed MM XII Damage virtually total |
