By Jeremy Lovell
London - With the devastation of last month's
Pakistan earthquake still fresh in the mind, scientists said on Wednesday
they have developed a way of predicting the size of a tremor even as it
starts.
Seismologists have tried and failed for years to predict
where and when quakes will happen and how big will they be.
Now
there is a glimmer of light on the horizon - at least for the latter goal,
according to scientists at the University of California,
Berkeley.
'We can determine the magnitude within a
couple of
seconds' | "We can determine the magnitude within a couple of
seconds of initiation of rupture and predict the ground motion from
seconds to tens of seconds before it is felt," said lead researcher
Richard Allen.
Although that time frame would be far too short for
people to react and evacuate, it could be enough to tell local emergency
services almost instantaneously the scale of the disaster they are likely
to be facing when the dust settles.
It could also set off alarm
bells in far flung centres who could begin to mobilise support
earlier.
Up to now, the cascade theory of earthquakes that portrays
them as acting like a row of dominoes with one action triggering another
in sequence, has meant it has been impossible to gauge the scale of the
quake until it has ended.
By that time, communications could well
have been destroyed leaving local emergency services in an information
black hole.
'You can predict the magnitude of an
earthquake before it has ended' | But the study led by Allen and co-author Erik Olson,
published in Thursday's edition of Nature science journal, uses a
different theory.
It suggests that the size, type and depth of the
first break on the fault line - that can be measured as it happens - gives
a very good indication of the earthquake's eventual reach.
"Most
seismologists are surprised, and frequently sceptical, that you can
predict the magnitude of an earthquake before it has ended," Allen said in
a statement from Berkeley.
"But this is telling us that there is
something very different from what we thought about the physics of the
processes involved in the rupture," he added.
In a commentary on
the research also published in Nature, Rachel Abercrombie of Boston
University said the new theory had crucial implications but that more work
was needed.
"We are far from understanding how onset, propagation
and state of stress of the surrounding fault interact to determine the
final size of a seismic event," she wrote.
"Olson and Allen's study
advances that understanding and thus our ability to predict an
earthquake's size before it reaches its peak," she added.
|