Magnetic clues in earthquake prediction
Renewed efforts are being made to discover whether it might be possible to predict earthquakes by measuring magnetic pulses from electrical discharges in the earth.
The idea is based on a theory that rock produces intense electrical currents when a quake is coming.
Tom Bleier, a satellite engineer with California-based research project QuakeFinder, which is funded by parent company Stellar Solutions, said the currents were huge, "almost like lightning underground".
His team has spent millions of dollars putting out magnetometers along fault lines in California, Peru, Taiwan and Greece.
The instruments can detect magnetic pulses from electrical discharges up to 16 kilometres away, National Geographic reported.
California's San Andreas fault might have 10 pulses on a normal day, but before a large quake that background level of static electrical discharges should rise sharply, Bleier said.
He had seen that pattern before half a dozen magnitude-5 and 6 quakes where he had been able to monitor the quake precursors.
Activity had risen to maybe 150 to 200 pulses a day, surging about two weeks before the quake, then dropping back to the background level until shortly before the fault slipped.
A problem for the theory is that magnetic pulses can be caused by many things, such as lightning, solar flares, electrical interference from highway equipment, or even a nearby farmer's tractor engine.
GNS Science seismologist Bill Fry was cautious about the QuakeFinder project.
The theory had been around for some years, being considered exciting in the 1990s when a considerable amount of work was done to find out whether the phenomenon was present in most quakes.
"The conclusion was that it really isn't," Fry said.
Recent interest in the work appeared to have followed a talk given last month at a professional meeting for geophysicists in San Francisco.
While the pulse theory was unlikely to be the most promising advance in hazard analysis, the research was probably worthwhile, Fry said.
Many discoveries had come from hunches that had not been well accepted by the scientific community.
A problem for the magnetic pulse theory was that it had been difficult, or impossible, to reproduce in the laboratory findings that were described in the literature, Fry said.
At the depths where quakes started there was a certain set of circumstances, such as pressure and the presence of saltwater fluids.
When those circumstances were included in laboratory experiments, researchers did not get the phenomena indicated by the theory.
He doubted that a way to predict quakes would be found in the near future.
"If it weren't such a complex problem, we would likely have a solution by now," Fry said.
"We see different things in different earthquakes. The crux is finding something that happens with every earthquake," he said.
- © Fairfax NZ News
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