A numerical scale for measuring the destructive power and major physical effects of an earthquake based on direct observation, modified for North American conditions. The Mercalli scale was first formulated by Giuseppe Mercalli in 1897.
Compare: Richter scale
Number Typical Results in an Urban Area
I hardly noticed by anyone including sensitive animals like birds
II suspended objects may swing slightly
III a slight rumble noticed by some people, especially if they are in a tall building
IV a noticeable vibration that rocks objects slightly
V felt by most people; small objects may fall
VI felt by everyone; windows and plaster may break; trees and furniture move
VII slight to moderate building damage; people knocked down; minor landslides
VIII moderate to severe damage to buildings; walls fall; trees break; some panic
IX extensive damage to buildings, foundations, and pipes; general panic
X roads crack; severe landslides; dams and bridges are severely damaged
XI major surface changes and collapse of roads, buildings, etc.
XII total damage to all roads, buildings, etc.; major changes to lakes, rivers, etc.
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