[Assam] Scientist Says Dam May Have Triggered China Quake/ From New York Times
cmahanta at charter.net
Wed Feb 4 23:22:23 IST 2009
Scientist Says Dam May Have Triggered China Quake
By THE ASSOCIATED PRESS
Published: February 4, 2009
Filed at 12:31 p.m. ET
BEIJING (AP) -- Pressure from a dam, its reservoir's heavy waters
weighing on geologic fault lines, may have helped trigger China's
devastating earthquake last May, some scientists say, in a finding
that suggests human activity played a role in the disaster.
The magnitude-7.9 quake in Sichuan province was China's worst in a
generation, causing 70,000 deaths and leaving 5 million homeless.
Just 550 yards (meters) from the fault line and 3.5 miles (5.5
kilometers) from the epicenter stands the 511-foot-high
(156-meter-high) Zipingpu dam, the area's largest. The quake cracked
Zipingpu, forcing the reservoir to be drained.
Fan Xiao, a chief engineer at the Sichuan Geology and Mineral Bureau,
said Wednesday that the immense weight of Zipingpu's waters -- 315
million tons -- likely affected the timing and magnitude of the
quake. Though earthquakes are not rare in the area, one of such
magnitude had not occurred for thousands of years, Fan said.
''I'm not saying the earthquake would not have happened without the
dam, but the presence of the massive Zipingpu dam may have changed
the size or time of the quake, thus creating a more violent quake,''
Fan said in a telephone interview.
Seismologists recognize that large bodies of water may exert pressure
on fault lines deep in the earth, leading to earthquakes. The
pressure can push the sides of fault lines harder together,
increasing friction, or cause the fault lines to slip apart.
Scientists have recorded smaller earthquakes possibly caused by
reservoirs. A magnitude-6.4 quake near India's Koyna dam killed at
least 180 people in 1967 and is thought to have been induced by the
Fan is among a number of experts who have voiced concerns in recent
months about the likelihood that Zipingpu may have contributed to
last year's quake. Their concerns were reported last month in Science
The Chinese government has portrayed the Sichuan quake as an
unavoidable natural disaster, and it has promoted the building of
large dams to meet the country's energy needs and reduce flooding.
The Three Gorges Dam, the world's largest hydroelectric project, was
built to end flooding in the Yangtze River and provide a clean energy
alternative to coal, but has instead been plagued with problems, from
resettlement to landslides.
Many scientists are not convinced that the Zipingpu dam caused the
Sichuan quake, even if it may have been a factor. Lei Xinglin, a
geophysicist at the government's China Earthquake Administration,
said reservoirs increase seismic activity but will not cause an
earthquake. He called for further investigation.
''A reservoir in the region will have positive and negative effects
on a potential earthquake, but it is ridiculous to say an earthquake
was caused by the dam,'' Lei said. ''In order to gain more knowledge,
we still need to carefully research this topic rather than jumping to
Lei said a fall in the Zipingpu reservoir's waters between December
2007 and the time of the earthquake and the penetration of water into
the fault line were ''major factors'' in the quake.
Roger Musson, a seismologist with the British Geological Survey, said
at best Zipingpu may have accelerated the timing of the quake.
''But the scale of the Wenchuan earthquake (185 miles, or 300
kilometers, of rupture) indicates that it was a true tectonic event
which would have occurred with or without the Zipingpu dam,'' Musson
said in an e-mail. ''It is thus only a question as to whether
stresses from the reservoir advanced the timing of the earthquake.''
Also calling for further investigation is Christian Klose, a
geophysical hazards research scientist from Columbia University in
New York. An abstract of a paper he presented at the American
Geophysical Union meeting in San Francisco in December said the added
weight weakened the fault below Zipingpu.
Fan, the Chinese engineer, said he was so convinced of Zipingpu's
potential dangers that he strongly opposed its construction in 2003,
worried that a disaster would devastate the Min River valley below.
He said he began pointing to the dam as a possible cause just a month
after the quake.
Still, many large dams continue to be built. Fan said he has
continued to write letters to government officials voicing concerns
about dams being built on the Dadu and Jinsha rivers to the west and
northwest of the quake zone.
More information about the assam