Charles Richter

Charles Richter was an American seismologist who, working at the California Institute of Technology, developed a practical numerical scale for measuring the size of earthquakes, published in 1935 and originally intended specifically for earthquakes in southern California recorded on a particular type of seismograph. Working closely with his colleague Beno Gutenberg, Richter based the scale on the logarithm of the maximum amplitude of seismic waves recorded on a seismogram, adjusted for the distance between the earthquake and the recording instrument, so that each whole-number increase on the scale corresponds to roughly a tenfold increase in recorded wave amplitude. Although the original local magnitude scale was eventually superseded for large or distant earthquakes by other magnitude scales that seismologists developed to address its technical limitations, the term Richter scale remained in wide popular use for describing earthquake size long afterward. Richter and Gutenberg also collaborated on the Gutenberg-Richter law relating earthquake frequency to magnitude, and Richter's 1958 textbook Elementary Seismology became a standard reference work in the field.