RIGHTER SCALE

Although no one knows how to prevent earthquakes, a gauge invented in 1935 by Charles Francis Richter (1900-1985) may give warnings of an impending disturbance so that measures might be taken to lessen the effect.
Richter, who gave his name to his invention, the Richter scale, was born in Ohio and attended the California Institute of Technology in Pasadena, where he became a professor of seismology. His colleague on his project to calculate the magnitude of an earthquake was Dr. Beno Gutenberg (1889-1960). The gauge they invented to assess the intensity of a quake is called a seismograph, an instrument that registers the amplitude of seismic waves emanating from its epicenter and the energy released by it. Ground motions are recorded and then calibrated by the scale.
The Richter scale operates on an indefinite scale from zero to infinity, which makes it a relative rather than an absolute scale. Waves close to zero are scarcely felt and do little damage. Damage begins to occur when the magnitude measures 3.5. Anything over 5 is considered serious. The highest reading ever recorded is 8.9, in a quake off the coast of Japan.
The moment-magnitude scale has largely replaced the Richter scale to measure earthquake energy.