An earthquake warning has been discounted: now Peru can relax
According to the first serious long-range earthquake forecast, massive shocks are due along the Peruvian coast this summer. But don't hold your breath waiting for them. The US National Earthquake Prediction Evaluation Council (NEPEC) has dismissed the forecast.
hus ends a chapter -- but not the entire story -- of one of the more spectacular episodes in the development of the highly uncertain art of earthquake forecasting. It remains to be seen whether or not nature will verify the prediction in spite of learned skepticism. But for now, the Peruvian government, which had asked the US government for the evaluation, can relax.
Meanwhile, the episode has proved the value of NEPEC, whose creation as a stand-by advisory group of eminent geophysicists might have been considered premature given the fact that reliable earthquake prediction still is not within sight. Be that as it may, when such a forecast is put forward in good faith by a recognized expert, the government of the region concerned must consider it. NEPEC exists precisely to help in deciding just how seriously to take it.
Brian T. Brady of the US Bureau of Mines, who has made the forecast, is a responsible scientist with an unorthodox theory. Basing his conclusions on laboratory studies of rock fracture, he believes there is a predictable development beginning with initial fracturing and ending in a collapse that produces a major quake.
Once the process starts, Brady claims, it's like starting a clock that runs at a more or less steady rate until the final collapse, according to a report of his theory in Science. That's why he believes he can predict Peruvian quakes this summer, using the quake pattern associated with a major shock near Lima in 1974 as a benchmark.
In a memo last May, he forecast a major quake this August and a second in May 1982. He has since revised this to predict both quakes this year -- one on Aug. 10 and a second on Sept. 15. He also anticipated foreshocks larger than magnitude 4.5 would occur near Lima last fall.
Seismologists generally have been uneasy with the precision and extended range of this forecast. Brady's theory seems unconvincing to most experts. NEPEC reflected this skepticism. Also the anticipated foreshocks didn't occur, although some minor tremors that were observed lead Brady to say that activity is picking up.
Brady is sticking to his prediction, although he reportedly would withdraw it if there were no significant pattern of foreshocks by this May.Certainly, we do not have long to wait to see whether or not he is right.
This would be merely an interesting scientific dispute were not the public safety involved. The Peruvian government had to decide whether or not to prepare for maj or disaster. Happily, NEPEC has laid that issue to rest.