Mercalli intensity scale

Mercalli intensity scale is a qualitative measure of earthquake severity based on observed effects rather than instrumental recordings. Developed by Italian volcanologist Giuseppe Mercalli in the late nineteenth century and later modified for American construction practices, the scale rates earthquakes from I (not felt) to XII (total destruction) according to human perception, building damage, and geological effects. Unlike the logarithmic Richter magnitude scale, which measures wave amplitude at a specific location, Mercalli intensity varies with distance from the epicenter and local ground conditions — a single earthquake can produce many different intensity readings across a region.\n\nThe scale's dependence on human observation and building standards makes it culturally and historically specific: a magnitude 6 earthquake in a region with rigid building codes may produce lower Mercalli intensities than the same earthquake in a region with unreinforced masonry. This is not a bug but a feature. The Mercalli scale measures what matters to civilization: not the energy released in the crust, but the damage done to the surface.\n\nThe Mercalli scale persists not because it measures earthquakes well, but because it measures human vulnerability honestly. A scale that requires collapsing buildings to reach its maximum is not a seismological instrument. It is a social diagnostic.\n\n\n\n