Monday, May 19, 2008

Just ten months before a deadly earthquake struck Sichuan Province's Beichuan county on May 12, a scientific study warned that the Chinese region was ripe for a major quake. After examining satellite images and conducting on-the-ground inspections of deep, active faults in Sichuan Province for more than a decade, scientists issued a warning.

"The faults are sufficiently long to sustain a strong ground-shaking earthquake, making them potentially serious sources of regional seismic hazard," the Chinese, European, and U.S. geoscientists wrote in the mid-July 2007 edition of the journal Tectonics.

They concluded that clashing tectonic forces were growing in Beichuan, ready to burst in an explosion of seismic energy.

With precision and what now seems like eerie foresight, the researchers charted the active faults on multicolored maps of Beichuan, which turned out to be the epicenter of the recent earthquake.

"As far as I know, this is the only investigation of these active faults," said study co-author Michael Ellis of the Center for Earthquake Research and Information at the University of Memphis in Tennessee.

(Related: "China Quake Delivered Seismic One-Two Punch" [May 15, 2008].)

The magnitude 7.9 quake that struck on May 12 almost entirely leveled parts of Sichuan Province. Chinese officials today estimated that the death toll would reach 50,000 and that nearly five million people are homeless.

"Locked in a Journal"

There is little reason to believe Chinese officials were aware of the July 2007 report, or that it would have made much difference if they had been.

"We had certainly identified the potential of these active faults," Ellis said. "But that information was effectively locked in an academic journal."

Ellis hopes that replacing the collapsed buildings with earthquake-proof structures could prevent future tragedies. "I've been to these little towns [before the quake]," Ellis said. "Most of the houses are built of unreinforced masonry, and you can see little brick factories all around this area.

"It is more expensive to build earthquake-proof structures," he added. And the vast majority of people in Sichuan Province are anything but rich.

The Science Behind the Quake

Earthquake activity is nothing new in Beichuan.

"We have shown evidence for surface-rupturing earthquakes along the Beichuan fault since 12,000-13,000 years ago," Ellis and colleagues reported last summer.

Speaking with National Geographic News, Ellis said, "Ultimately, the [2008] earthquake is related to the continuing and inexorable collision of India with Asia, which is occurring at a rate of about 20 to 22 milimeters [just under an inch] per year."

This collision started more than 50 million years ago, when the tectonic plate beneath India crashed into the Eurasian plate. (Watch how the plates slammed into each other.)

"The Himalayas and all of Tibet was created by this collision," Ellis added.

As the Indian plate continues its slow-motion crash into Asia—sometimes in jerks marked by earthquakes—it is pushing the entire Tibetan Plateau northward.

"This earthquake was the Tibetan mountains moving east over the plains of Chengdu [the capital of Sichuan Province]," said Roger Bilham, a geoscientist at the University of Colorado who was not involved in the July 2007 study.

Not Just Sichuan's Problem

Study co-author Ellis said that, as the Tibetan Plateau moves northward, "the interior parts of Tibet are collapsing, rather like a soufflé taken out of the oven into cold air."

Faults along the southern, Himalayan edge of Tibet present hazards as great as those underlying the Sichuan temblor, Ellis said.

"Risk associated with the loss of collateral and lives is very high along the Himalaya, because so many people live there or immediately downstream," Ellis added.

"The risk is similarly high in Sichuan [to the east], because of the population and, like India and Nepal, the relatively poor building standards," he said.

And as India continues to pound into Tibet, "it is still creating new fault lines"—and new dangers.

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