Keiiti Aki, 75, Is Dead; Developed a Way to Measure the Strength of an Earthquake
NY Times
Dr. Keiiti Aki, a seismologist whose penetrating studies of the behavior and origins of earthquakes contributed to a deeper understanding of natural disasters, died May 17 on Réunion island in the Indian Ocean. He was 75. The cause was a brain hemorrhage suffered after a fall, said a close friend, John K. McRaney of the Southern California Earthquake Center, where Dr. Aki had been a director.
In a career that spanned the earth sciences, Dr. Aki, a resident of Réunion, east of Madagascar, was interested in applying methods of quantitative analysis to shape theories in seismology. He was widely known for his concept of the “seismic moment,” which he developed in the 1960’s as a means of measuring the magnitude of earthquakes.
While studying a huge earthquake that struck Niigata, Japan, in 1964, Dr. Aki devised a calculation that considers the area affected by an earthquake, the rigidity of the underlying rock and the distance the rocks slip. The result - the seismic moment - is a measure of the energy released by an earthquake, and is used in addition to the moment magnitude scale, now the standard measurement announced to the public after disasters like the earthquake-generated tsunamis in December.
