Rating an Earthquake

Newspaper reports of earthquakes often indicate their force in terms of numbers on the Richter Scale. But what do these ratings indicate in the effects caused?

Running through the numbers 1 to 8 on the Richter Scale, the effects are these: 1 - quake detectable only by seismographic measurement; 2 - hanging objects swing slightly and a few people might feel the tremor; 3 - people indoors feel some vibrations; 4 - buildings tremble and glassware breaks; 5 - furniture overturns and pictures fall from walls; 6 masonry cracks, some houses cave in, windows break and chimneys fall; 7 extensive damage to dams, dikes and bridges, with many buildings collapsing; 8 - all structures receive catastrophic damage.

The earthquake in Peru occurring on May 31, 1970, in which more than 50,000 persons were killed and 800,000 left homeless, measured 7.8 on the Richter Scale.