Quake may have made Ranong fault active


Geographic modelling suggests the December 26 earthquake may have moved the island of Phuket 15 centimetres to the southwest, academics at Chulalongkorn University said yesterday.

They said the change would greatly affect the country’s geographic survey, because landforms on the surface of the planet usually only move about 1 millimetre a year.

Dr Itthi Trisirisattayawong heads a team surveying the geographic effects of the quake and subsequent tsunami. The academics and the Army’s Map Department were heading to Phuket late yesterday to begin three weeks of measuring.

Meanwhile, geologists are conducting an undersea survey to determine whether a fault off Ranong has become active again. A steady stream of air bubbles is surfacing 500 metres offshore in Laem Son Bay. They have been visible for about 10 days.

Muang Ranong district chief Chanat Kaewbamrung said yesterday he alerted the Mineral Resources Department to the phenomenon after local officials detected a seven-centimetre wide crack in the ocean floor about 1km long and bubbles were pouring from it.

The fault line is about seven metres underwater, he said.

Lerdsin Raksasakulwong, director of the department’s Geology Office, said the Ranong fault, which had been inactive for years, straddled the area where the ocean floor appeared to have split open.

“It’s possible that the December 26 earthquake has revived the dormant Ranong fault. When a fault becomes active, it releases bubbles,” he said.

Published on January 20, 2005

Sirinart Sirisuntorn

The Nation