Globe

Indonesian coral chronicles a history of massive earthquakes

July 22, 2012

By ERI GOTO/ The Asahi Shimbun GLOBE

Shapes in the coral in the Sumatra Basin have left a terrifying message for Indonesians.

Kerry Sieh and Danny Natawidjaja studied patterns in the reefs created by hundreds of years of seismic activity and believe the area may be entering a high-activity phase that could hammer the area with a series of massive earthquakes.

When a large quake occurs, the seabed in the basin is lifted, pushing some parts of the coral reef above the ocean surface. That exposed area stops growing but the submerged part continues to thrive, marking the coral with patterns that Sieh and Natawidjaja believe chronicle the area’s frightening geological history.

They have found that every 200 to 250 years, there was a recurring period lasting around 35 years during which several magnitude-8.0 and magnitude-9.0 quakes occur.

As a magnitude-8 temblor already occurred in 2007 there is a possibility that this dangerous period has begun.

"There will be an M8.8 earthquake in these waters during the next 30 years," predicts Earth Observatory of Singapore director Sieh.

The pair’s coral-based research already has an attentive audience in Indonesia. In the summer of 2004, Sieh and Natawidjaja, who works at the Indonesia Institute of Sciences, used the same techniques as the basis for a prediction that a “great earthquake will occur here in the Sumatra Basin in the near future."

Late that year, a massive magnitude-9.1 earthquake hit off the coast of Banda Aceh on the western side of the island of Sumatra. The tremors and the resulting tsunami took the lives of over 200,000 people across the region.

Although Sieh and Natawidjaja had not foreseen the exact location and timing of the earthquake, there words were interpreted in Indonesia as a forecast the coming catastrophe.

Now, with memories of 2004 still haunting the nation, the Indonesian government is trying to develop early warning systems to save lives when the next quake hits.

"If we can understand what happened in the past, we can predict what'll happen in the future and prepare for it," says Sieh.

Since the earthquake in 2004, modern seismographs have been deployed in Indonesia with support from countries including Germany and Japan.

"The quake stimulated earthquake research in this country," says Sri Widiyantoro, Bandung Institute of Technology (ITB) Faculty of Mining and Petroleum Engineering dean.

A key focus of current research is the Lembang Fault outside Bandung City, the state capital of West Java.

The 30-km fault, which had been relatively neglected by researchers, became a cause for concern when a M6.2 earthquake hit Java's ancient capital Yogyakarta in central Java in 2006, killing more than 5,000 people.

More than 2 million people live in the central part of Bandung City, so an earthquake along the Lembang Fault could result in massive casualties. Indonesian Institute of Science geologist Eko Yulianto worked with Japan's National Institute of Advance Science and Technology on a study of strata near the fault and determined that magnitude-7 earthquakes occur on a cycle of several thousands of years.

"We don't know when the next one will be," says Yulianto. "We should envision a worst-case scenario."

The Indonesian Meteorology, Climatology and Geophysics Agency now has an observation room that monitors seismographs and tide indicators around the country.

"Using a variety of methods, we ascertain the regions where there is an earthquake risk, and consolidate observation of those regions," explains Suhardjono, director of the Agency's Earthquake and Tsunami Center.

But the ITB’s Widiyantoro, who has studied at Kyoto University and Tokyo University's Earthquake Research Institute, cautions that Indonesia still has a lot of work to do.

"We want to gain the ability to foresee earthquakes, but for the time being in this country, our main priority is disaster prevention and reduction when they actually hit,” Widiyantoro says. “We want to create systems that will provide emergency earthquake warnings and stop trains when tremors are detected. We're chasing after Japan."

By ERI GOTO/ The Asahi Shimbun GLOBE
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The earthquake that hit the Sumatra Basin in 2004 had a magnitude of 9.1, more powerful than the Great East Japan Earthquake (M9.0). (Asahi Shimbun file photo)

The earthquake that hit the Sumatra Basin in 2004 had a magnitude of 9.1, more powerful than the Great East Japan Earthquake (M9.0). (Asahi Shimbun file photo)

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  • The earthquake that hit the Sumatra Basin in 2004 had a magnitude of 9.1, more powerful than the Great East Japan Earthquake (M9.0). (Asahi Shimbun file photo)
  • "We ascertain the regions where there is an earthquake risk, and consolidate observation of those regions," says Suhardjono, director of the Indonesian Meteorology, Climatology and Geophysics Agency's Earthquake and Tsunami Center.

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