Seismologists tracking Indonesian quakes get a taste of the real thing

The Jakarta Post

PADANG (AP): American seismologist John Galetzka grabbed his video camera and screamed as the beach trembled violently beneath him. Despite the danger, he was not about to miss what could be the most deadly natural disaster of our time.

"Ooooohh! This is the big one!" whooped the scientist, who plopped down on the sand to film coconuts shaking out of trees as Wednesday's magnitude 7.9 quake hit.

Galetzka has spent nearly a decade studying this fault off Sumatra island - the world's most active - and believes it is ready to explode, leading to a potential repeat of the 2004 Indian Ocean tsunami that killed 230,000 people. Or even something worse.

Last week's powerful temblor shook four Southeast Asian countries, triggered two massive aftershocks and spawned a 3-meter-high tsunami. It killed 23 people and injured at least 88 more, but it was not the megathrust Galetzka and others have been fearing.

The activity did, however, put even more tension on the so-called Mentawai island patch - a nearly 300-kilometer stretch along the volatile fault - that pops about every 200 years.

It last snapped in 1833, according to research by the California Institute of Technology's Tectonics Observatory, causing a quake of around magnitude 9.0.

"Whether it cuts loose a few minutes from now, or next month, or another 10 or 20 years, that's the big question," said Galetzka, a CalTech research assistant, who was setting up a monitoring station on Siberut island when the quakes hit. "But we are a huge step closer. I think it's just around the corner."

The island is perched directly atop the Mentawai patch, about 150 kilometers off western Sumatra's coast.

Indonesia, the world's largest archipelago, is prone to seismic upheaval due to its location on the "Ring of Fire," an arc of volcanos and fault lines encircling the Pacific Basin.

The most closely watched fault is the meeting point of the Eurasian and Pacific tectonic plates, which have been pushing against each other for millions of years. The magnitude 9.0 quake that set off the 2004 tsunami was centered along that line, and more than two-thirds of those killed in 12 nations lived in Aceh province, on Sumatra's northern tip.

Last week's quakes were also centered along that fault, but they formed a circle around the Mentawai island section that Galetzka and others worry so much about. That means the pressure continues to build there.

Padang, a low-lying seaside city of 900,000 people, is expected to take the heaviest hit next time a big one strikes, with authorities fearing up to 100,000 will be unable to escape giant waves that could once again surge across the Indian Ocean at jetliner speeds.

Many people said a public awareness campaign launched after the 2004 tsunami paid off, with warnings issued over mosque speakers and training provided by local officials on how to escape a disaster.

But some complained they received no official warning this time.

"I'm more afraid than ever of a tsunami," said Yurizal, a 31-year-old brick maker from Kota Agung village who felt the strong tremor but heard no warnings after. "We need sirens or something before it's too late."