Successfully predicted earthquake.

Successfully predicted earthquake

In May of 1985, seismologists Max Wyss and Robert O. Burford predicted that within a year, an earthquake would occur along a small section of the San Andreas fault located near Monterey, Calif. And on May 31, 1986, a magnitude 4.6 quake shoot that specified region. This was the first successful earthquake prediction for the San Andreas fault, report the researchers in the Sept. 24 NATURE.

The researchers based their forecast on a drop in the seismicity of the area--a technique that has been successful in predicting two other earthquakes, says Wyss, from the University of Colorado at Boulder. He and Burford, from the U.S. Geological Survey in Menlo Park, Calif., also calculated that another section of the fault would rupture by May of 1986; this event never occurred.

According to Wyss, the successful prediction was quite accurate in terms of location and size, but the researchers could not pinpoint the time of the quake to less than a year. The researchers say seismologists will use this technique successfully in the future to predict larger earthquakes, "but the major segments of the San Andreas fault near San Francisco and Los Angeles have such low background seismicity rates' that any drop in those rates--which might signal a future quake --would be difficult to detect.