Geologist says serial Sumatran quakes a surprise


Bangalore : Big earthquakes pounding Indonesia like clockwork for the last three days have surprised Indian geologists, who say the tremors go on for some time.

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“It looks like its not going to stop for some time,” said Vineet Gahalaut, a senior seismologist at the National Geophysical Research Institute in Hyderabad.

Three big quakes and dozens of aftershocks since Wednesday’s 8.4 magnitude quake – the world’s biggest this year – originated from a patch called the ‘Mentawai section’ southwest of Indonesia’s provincial capital Padang.

“It is becoming a remarkable series of earthquakes, in which one event is probably increasing the stress in the neighbouring region and triggering the next event,” Gahalaut told IANS.

He said the epicentre was moving towards south-southeast.

“All of us now know that the region where Wednesday’s event occurred was the region (Mentawai section) where we expected a great earthquake. But these earthquakes keep occurring elsewhere,” said a surprised Gahalaut.

For instance, he said, the 9.1 magnitude killer quake that caused the tsunami in December 2004 occurred in the Sumatra-Andaman section while the 8.6 magnitude quake in March 2005 originated in what is known as the Nias section.

It is impossible to say where it could be the next. “But now there are only two regions left out in Sumatra-Andaman region. One, off the coast in southern Sumatra and the other one, the Siberut Island region.”

The Siberut Island region lies between the epicentres of last Wednesday’s quake and the one that originated in Nias in 2005.

“I do not think that this series can propagate further into Java region as the Sumatra Fault System seems to bifurcate the frontal arc near the southern tip of Sumatra,” Gahalaut said.