Tuesday, June 07, 2005 The massive quake that hit Nias island on March 28 has altered its position.

Based on a LIPI study, the island shifted 12 meters westwards, away from Sumatra, a few seconds after the quake.

Telo island in the Batu islands moved 70 centimeters farther away from Sumatra.

Danny said that before the quake, Nias island was moving toward Sumatra at a rate of 3 centimeters per year due to the depressing of the continental plate by the oceanic plate, at the end of which Nias island is located. The pressure was released during the quake, which resulted in Nias shifting away from Sumatra.

A joint team from LIPI’s Geotechnology Research Center and the California Institute of Technology has been conducting seismological research on the west coast of Sumatra since 1993. The movements of tectonic plates are measured by the Global Positioning System (GPS).

The team has installed 19 GPS monitors in 19 locations on Sumatra’s west coast from Muko-Muko in Bengkulu to Aceh. Some have been installed on islands off the west coast of Sumatra, from Enggano in Bengkulu to Simeuleu in Aceh.

The team installed nine telemetric devices connected to the GPS last week to obtain satellite data so that they do not have to actually visit the GPS locations any longer to recover the data.

In addition, the team has also positioned nine seismographs at those locations and five accelerographs on Mentawai and Nias, and in the Simeuleu islands.

An accelerograph is a device used to measure and record massive quakes. A seismograph can usually only record seismic tremors of up to 7 magnitude, but an accelerograph is able to record tremors of 9 magnitude and over.

–Sfofiardi Bachyul Jb

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