First seconds of a quake can show its size
* Predicted time frame could tell emergency
services the extent of damage they will face
LONDON: With
the devastation of last month’s 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 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.
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. reuters
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