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Earthquake prediction a step closer: scientis -

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EMMA ALBERICI: Scientists in the US have been able to measure minute geological changes in the
earth that could one day help to predict earthquakes.

The team of seismologists dropped sensor equipment into holes drilled one kilometre deep into
California's San Andreas fault.

They then recorded changes in the speed of seismic waves - some up to 10 hours before a small
earthquake struck.

The scientists hope this leads to a prediction system that could one day give people hours to
evacuate buildings ahead of earthquakes.

Jennifer Macey reports.

JENNIFER MACEY: There's a small town in California called Parkfield that's perfect for American
seismologists to observe changes in the earth's crust just before an earthquake hits.

Dr Paul Silver of the Carnegie Institution for Science in Washington explains.

PAUL SILVER: This is a town of 19 people that happens to sit on the San Andreas fault - right
between LA and San Francisco. And it's a place where every 20, 25 years or so there's a magnitude
six earthquake, it doesn't hurt very many people or anything but it's fairly regular.

So we've put a lot of instrumentation there to try to catch a possible precursor, to try to just
study in general the earthquake problem and the earthquake cycle through this 20, 25 or so years.

JENNIFER MACEY: He says a team of researchers lowered sensitive instruments into a well dug one
kilometre below the surface and monitored any geological changes over two months.

They were able to record slight changes in the speed of seismic waves and at one stage they
recorded a signal ten hours before a magnitude three earthquake struck on Christmas Eve in 2005.

The results have been published in the latest Nature journal. The lead author of the report is
Associate Professor Fenglin Niu of Rice University in Texas.

FENGLIN NIU: The speed, how fast the wave travels, it depends on the stress applied to the loch. So
if you have the same material under high pressure, then the wave will travel faster. And if looking
at the time between the earthquake and our signals actually interestingly the velocity changes
start ten hours before the magnitude three earthquake, and two hours before the magnitude one
earthquake.

JENNIFER MACEY: The scientists are now planning more experiments to test these pre-seismic signals.

Dr Paul Silver says scientists have tried to record these waves since the 1970s, but advances in
technology have allowed them to make more precise and reliable measurements. He says it's a key
step towards predicting major tremors.

PAUL SILVER: There's more instrumentation available, there are new phenomena being discovered sort
of as a result of this. This I think is an indicator of a whole spectrum of behaviours that if we
understand them, of this slow earthquake variety, I think we may be able to ultimately predict
earthquakes.

KEVIN MCCUE: Well that's true, if you have the money.

JENNIFER MACEY: Kevin McCue is the director of the Australian Seismological Centre and an adjunct
professor at the University of Central Queensland.

He says while this prediction system could be applied along well-known faults it may be less
effective where an earthquake strikes seemingly randomly such as Newcastle.

KEVIN MCCUE: And there are some great areas of the world where we know reasonably well what the
tectonics are - where the major earthquakes occur on the faults. But in an area like Canberra or
Sydney, Newcastle for example, we have no idea which, if any faults are active or not, where the
earthquake might be.

JENNIFER MACEY: And he says a dense network of bore holes and instruments are needed for this
system to be effective.

KEVIN MCCUE: So it's probably feasible to do on parts of the San Andreas fault in California where
this is a) a lot of money and b) a lot of already existing instrumentation. And also the bore holes
which are so critical to put the instruments not on the surface but down a bore hole to be
measuring the waves that travel through, directly through the volume of rock that may rupture in a
future earthquake.

So you've got to be constantly measuring the velocity of these waves as they travel through the
area. And it may be weeks to even months before a very large earthquake.

EMMA ALBERICI: Kevin McCue the director of the Australian Seismological Centre ending that report
by Jennifer Macey.