A measure of the intensity of an earthquake. This is a subjective value that varies depending on where the earthquake is observed. The ratings vary from I (felt only under especially favourable circumstances) to XII (total destruction).
|I||Generally not felt.|
|II||Felt by a few people, suspended objects may swing.|
|III||Felt by a few people, similar vibration levels to a passing truck.|
|IV||Felt by most people indoors, but few outdoors. Windows, doors and dishes rattle.|
|V||Nearly everybody will feel it. People woken and small objects may topple.|
|VI||Felt by everyone, heavy furniture moves, books fall from shelves, bushes and trees visibly shake.|
|VII||Difficult to stand. Some damage to poorly constructed buildings, tiles and loose bricks fall. Small landslides on slopes. Water becomes turbid.|
|VIII||Difficult to steer a car. Damage to good buildings, chimneys. Tree branches break and steep slopes crack.|
|IX||Extensive building damage, underground pipes break.|
|X||Most walls destroyed, large landslides, water thrown from rivers and lakes onto the banks.|
|XI||Most masonry buildings destroyed, railroad tracks bent and most underground pipework destroyed.|
|XII||More or less total destruction, objects thrown into the air.|
Roman numerals (I-XII) to avoid confusion with magnitude estimates on the Richter scale.
The scale is named for the Italian geologist Giuseppe Mercalli (1850-1914), who devised the first version in 1902.