Expert warns of collapse zone in mudflow-affected Sidoarjo

Indra Harsaputra ,  The Jakarta Post ,  Sidoarjo, East Java   |  Thu, 07/23/2009 7:51 PM  |  National

Land subsidence that caused a house to sink in West Siring, Sidoarjo, recently may be indications of another disaster, potentially turning areas surrounding the mudflow into a collapse zone, an expert warns.

Such a disaster could see hundreds of houses and the Porong highway sinking dozens of meters beneath the earth, potentially killing many people, Geologist Andang Bachtiar said Thursday.

“We must be wary of such natural phenomenon,” said Andang, a former chairman of the Indonesian Geologists Association.

The recent land subsidence was a preliminary sign of a collapse zone, he said.

Quoting seismic data from Lapindo Brantas Inc., the company blamed for the mudflow, Andang said a similar phenomenon had occurred in the Porong area in during the Pleistocene-Holocene age between 1 million and 11,000 years ago. The collapse zone then created a caldera six kilometers in diameter and between 100 and 300 meters deep.
 
If a collapse reoccurred, Andang said, it could affect a 6 kilometer radius around the Panji 1 well, from which hot mud has been spewing since May 2006.

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