Seismology: The sleeping dragon

Source of photo: http://internationalrivers.org/en/sichuan-earthquake/sichuan-earthquake-may-2008?size=_original

The great Sichuan earthquake of 12 May 2008 caught Earth scientists off guard. Tucked below towering hillsides in Bailu, in China's Sichuan province, two school buildings face one another across a courtyard. Both are several storeys high, white with cheery light-blue trim. It's a peaceful April day, cool and humid; a rubbish bin shaped like a penguin sits at the side of the courtyard, as if waiting for someone to toss in a candy wrapper. But no one will be feeding the penguin today. That's because a nearly 2-metre-high ridge of buckled and uplifted concrete runs right through the courtyard, a manifestation of the geological faults that spawned the great Sichuan earthquake of 12 May 2008.

Along the third side of the courtyard is a ghost. It is a pile of brick rubble, all that remains of another building that collapsed in the quake. There, geologists are hunting for clues to what happened on that day, digging a 40-metre-deep trench to search for signs of past quakes that emanated from these faults.

These cracks in Earth's crust are deceptive pieces of geology. Both Chinese and Western scientists had mapped them before but failed to recognize their potential. "I was astonished at this quake," says Xu Xiwei, deputy director of the Institute of Geology at the China Earthquake Administration in Beijing. The buildings that collapsed and the landslides and mud flows that buried towns combined to kill at least 70,000 people and cause widespread ecological damage (see "Panda's in Peril")

More so than other quakes, this one has uncovered gaps in earthquake hazard research, both in China and elsewhere. When scientists assess seismic risk, they tend to focus on the faults that move the most and produce large earthquakes often. That strategy pays off with the many quakes that play by the rules. In western Sichuan, however, it turned out to be disastrously wrong.

One year later, researchers are probing the deadly faults in the hope of finding ways to avoid repeating their mistakes. In retrospect, they say, the geology of the Longmen Shan, or Dragon's Gate Mountains, was trying to warn them.

To read the remainder of this article go to: http://www.nature.com/news/2009/090513/full/459153a.html