Mercalli scale
mer-KAH-lee
A seismic intensity scale that measures earthquakes not by the energy released but by the effects observed — what people felt, what objects moved, what structures failed. The scale runs from I (not felt) through XII (total destruction), and every level is defined by human experience: at IV, dishes rattle and sleepers wake; at VI, furniture moves and plaster cracks; at IX, buildings collapse. The Mercalli scale is the human measure of earthquakes — it asks not how powerful the quake was, but what it did to people and the things people built.
Etymology
Named for Italian volcanologist Giuseppe Mercalli, who developed an early version in 1884. The current Modified Mercalli Intensity Scale (MMI) was refined by Harry O. Wood and Frank Neumann in 1931.
Notes
The Mercalli scale and the Richter/moment magnitude scale measure different things. A single earthquake has one magnitude but many intensities — strongest near the epicenter, weaker with distance.
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