Science: The Mechanism of Earthquakes

Earthquakes seem to happen at random; they seldom give advance warning, and cannot be predicted with any certainty. Last week Professor Hugo Benioff of CalTech explained his theory that all great shallow earthquakes (originating in rock slippage less-than 45 miles below the surface) have a common cause and are released by a single "mechanism."

Geophysicists have long thought that earthquakes are caused by a sudden release of strain (distortion) in the earth's crust. Dr. Benioff studied the records of all major earthquakes since 1904 and made a chart of their "strain-rebound" characteristics. Somewhat to his surprise, the chart made a regular, sawtooth...