China has too high an earthquake risk acceptability to prevent mass devastation

Britain News.Net
Wednesday 14th May, 2008 (ANI)

London, May 14 : If reports are to be believed, the seismic code for Sichuan, the south-western Chinese province where a devastating earthquake stuck on May 12, substantially underestimated the strength of the quake.

The earthquake, which killed about 10,000 people, measured 7.9 on the Richter Scale.

According to a report in New Scientist, China's earthquake regulations class the south-western Chinese province as equivalent to a 7 on the Mercalli intensity scale, which uses historical information to assess risk of damage from earthquakes.

Intensity 7 on the scale means that there is a 10% risk of an earthquake occurring once in 50 years that will be powerful enough to make it difficult for a person to stand up, but cause only negligible damage to well-constructed buildings.

But, the May 12 quake would be classified on the Mercalli scale as a 10 or 11.

"The seismic code for the area substantially underestimated the earthquake strength," according to Hong Hao, a civil engineer at the University of Western Australia in Perth.

Buildings in Sichuan, China, were constructed to withstand an earthquake roughly one-fifth as powerful as the one that hit the region on May 12.

It's unlikely that the existing building regulations, which would require buildings to be reinforced, were always followed, particularly in the countryside where people cannot afford to follow the regulations," according to Hao.

The devastation caused by the Sichuan earthquake raises questions about whether the accepted level of risk is too high.

"All around the world, buildings are designed to withstand ground motion that has a greater than 10% risk of occurring in 50 years," said Kevin McCue, director of the Australian Seismological Centre in Canberra. "That's considered too high a risk for dams and nuclear reactors," he added.

The Sichuan area is not new to big earthquakes.

In 1933, a 7.5-magnitude quake hit the area, destroying the town of Diexi and surrounding villages, and killing over 9000 people. In 1976, a 7.6-magnitude earthquake hit Tangshan, in the northeastern province of Hebei, killing about 240,000 people.

The Sichuan quake is believed to have killed at least 10,000 people, with 80% of the buildings collapsing.

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