Richter, Charles

Richter, Charles (1900–85) Charles Richter spent his career studying earthquakes, both worldwide and along the faults of southern California, where he was a professor at the Seismological Laboratory of the California Institute of Technology. He is best known for devising the famous ‘Richter Scale’ of earthquake magnitudes, a universal measure for comparing widely separated earthquakes. Since earthquakes can range from subtle tremors to fault ruptures that extend hundreds of kilometres, Richter chose a logarithmic scale, calibrating the seismic waves from southern California tremors as recorded by standardized seismographic equipment. At the present day, nearly all research seismometers record digital signals that are stored on computer. In Richter's day, seismic waves were recorded by a swinging pen on a sheet of paper that rotated on a cylindrical drum. The ‘Richter magnitude’ was computed by measuring the pen's swing in millimetres, taking its logarithm, and applying a correction for the distance between station and earthquake. Working in the 1930s and 1940s with Beno Gutenberg, another professor at the Seismological Laboratory, Richter extended his scaling algorithm from near-by to worldwide earthquakes. Later refinements have tied the Richter scale to the actual energy released by an earthquake. Each unit on the Richter scale represents a thirty-fold increase of energy. The largest earthquake since the inception of the scale occurred on 22 May 1960 along the coast of Chile, with estimated magnitude 9.5.

As a public spokesman for seismology and earthquake hazard mitigation, Richter often showed an irascible personality. His renowned 1958 textbook Elementary seismology contains many pithy comments and admonitions against sloppy research methods. Ironically, many of his personal records were destroyed in a house fire that followed the Northridge earthquake of 17 January 1994 (magnitude 6.6) north of Los Angeles.

Jeffrey Park