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'Megathrust quake could hit Asia 'at any time'
Washington:
A new research has suggested that a devastating
"megathrust" earthquake could occur at any time off
the Indonesian island of Sumatra. Using GPS, field
measurements, radar data and seismological records,
a team of international researchers investigated the
parameters and reconstructed the events of two massive
earthquakes, measuring 8.4 and 7.9 on the Richter
scale, which occurred in the Mentawai area in 2007.
Previous models of how earthquakes work had suggested
that the same fault would rupture in the same way
and at regular, predictable time intervals. But, the
researchers found that the 2007 quakes ruptured only
a fraction of the area affected by the giant 1833
earthquake, indicating that a tectonic plate boundary
can rupture in different patterns depending on local
differences in stress. "What we see here is that the
2007 earthquake had at least a very big overlap with
the 1833 earthquake, but it was very much smaller;
in other words, it was an entirely different earthquake,"
said John McCloskey, a geophysicist at the University
of Ulster, UK.
The
GPS data enabled the researchers to create a map of
the fault zone, showing which parts were locked tight
and which parts were slipping freely. This allowed
them to estimate where the most strain has built up,
and where the next big rupture is most likely to occur.
The results suggested that the 2007 events released
only a quarter of the energy that had accumulated
since 1833, leaving enough pent-up energy to trigger
another giant earthquake at any time. This event could
be anything between magnitude 8.2 and over 9, according
to McCloskey. According to geologist Jean-Philippe
Avouac, director of the Tectonics Observatory at the
California Institute of Technology (Caltech), "There's
still enough strain to create another major earthquake
in that region. We may have to wait a long time, but
there's no reason to think it's over."
- Dec
4, 2008
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