U. S. project to predict quakes fails

STUDY 11 YEARS OFF THE MARK

PARIS •

A prolonged attempt to help scientists predict when earthquakes will happen has ended in failure, according to a study published today in Nature, the British science weekly.

The paper — whose publication coincides with the aftermath of the quake that struck Pakistan and India, killing tens of thousands of people — is based on a long-term project in California.

Scientists sowed a 40-kilometre part of the notorious San Andreas fault, located at the city of Parkfield, with scores of seismic sensors to monitor earth rumbles and movement in real time.

But an earthquake measuring 6.0 on the Richter scale struck that region on Sept. 28, 2004, without any warning. There was not the slightest hint of a buildup of strain or impending landslip.

Parkfield had long been fingered as a good testbed for earthquake physics as it had experienced seven big quakes since 1857, and these events were quite evenly spaced apart.

Because of that, the U. S. Geological Survey felt confident enough in 1985 to predict that a 6.0 quake would occur in Parkfield before 1993.

As it happened, the USGS was spot-on when it came to predicting the size of the event and the location, and the data sent back by the sensors were invaluable — but its timing was 11 years out.

In addition, the absence of any precursor signal meant the local population could not be warned in time.

“Earthquake prediction is the Holy Grail of seismology,” says the report, adding, “The 2004 Parkfield earthquake, with its obvious lack of precursors, demonstrates that reliable short-term earthquake prediction is still not achievable.”

Given the huge task of achieving predictability, the study recommends that resources be devoted more to improving computer models to help calculate how big a future quake will be and what kind of ground motion it is likely to cause.

This would have immediate benefit for people living in the vulnerable area and for rescue services.

The new study is lead-authored by William Bakun of the USGS, based at Menlo Park, Calif.