Before there were seismometers which could measure the vibration of the earth caused by earthquakes, scientists used descriptive measures of the effects of the vibration as a means of quantifying their size or severity. One of the first intensity scales was developed by the Italian scientist De Rossi and the Swiss scientist Forel, known as the Rossi-Forrel scale. In 1902 the Italian scientist Mercalli improved this scale, and in 1931 the American scientists H.O. Wood and F. Neumann adapted the scale for use in California. The scale is now known as the Modified Mercalli Intensity scale.
| Modified Mercalli Intensity Scale of Earthquake Damage | |
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Total destruction; "waves" seen on ground surface; river courses altered; vision distorted |
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Railway tracks bend; roads break up; large cracks appear in ground; rocks fall |
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Most buildings destroyed; large landslides; water thrown out of rivers |
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General panic; damage to foundations; sand and mud bubble from ground |
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Car steering affected; chimneys fall; branches break; cracksin wet ground |
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Difficult to stand; plaster,bricks, and tiles fall; large bells ring |
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People walk unsteadily; windows break; pictures fall off walls |
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Doors swing; liquid spills from glasses; sleepers awake |
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Dishes rattle; standing cars rock; trees shake |
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Shaking felt indoors; hanging objects swing |
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People at rest upstairs notice shaking |
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Vibrations are recorded by intruments only |