Quake moved Sumatra by only 20 cm: Scientists

After the tsunami, the Indonesian islands did not really move dozens of metres as previously feared.

The Indonesian islands of Sumatra moved only 20 centimetres on average after last month's Asian earthquake and tsunami, and not dozens of metres as previously feared, media reported, quoting calculations by the Danish Space Centre.

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The new numbers, reported on television channel TV2's website, vary greatly from reports in the days following the devastating December 26 earthquake that the tip of the Sumatra island may have moved by as much as 36 metres.

US Geological Survey scientist Ken Hudnut said on December 27 that some of the smaller Sumatra islands may have moved about 20 metres while the northeastern tip of the Indonesian territory could have slid about 36 metres to the south-west after the quake, which measured 9.0 on the Richter scale.

Scientists Shfaqat Abbas Khan and Olafur Gudmundsson of the Danish Space Centre, who used a GPS satellite system to determine the extent of the plate movement following the earthquake, have however since found that the island did not move more than 20 centimetres on average.

"For the Sumatra earthquake there were horizontal moves of about seven metres around the crack area. But that area is about 200 to 300 kilometres west of Sumatra, so Sumatra itself could only have moved about 20 centimetres," Khan told TV2.

The two Danish scientists' findings also contradicts a report from the Malaysian Navy published yesterday stating that the depth in certain stretches of the narrow Malacca Strait, one of the world's busiest shipping lanes, had changed by as much as two metres after the quake.

"The GPS observations show that the Malacca Strait near Sumatra basically hasn't changed," Khan said.