CHENGDU, China — China mobilized 30,000 additional soldiers to the earthquake-shattered expanses of the nation’s southwestern regions on Wednesday — not just to help victims, but also to shore up weakened dams and other elements of the infrastructure whose failure could compound the disaster.
Experts said that these dams were built around the well-recognized Longmen Shan fault. They warned that such dams might have sustained damage that could cause them to fail even weeks later.
Much depends on efforts to reduce the menacing pressure of water behind the dam walls. Two thousand soldiers were sent to a dam just three miles upriver from the devastated town of Dujiangyan, northwest of the provincial capital of Chengdu, to inspect a structure that has shown some cracks and is “in great danger,” according to state-controlled China National Radio.
Dams and their electric generators are only the most visible aspects of the infrastructure battered by the earthquake: The region also is the site of the cities of Guangyuan and Mianyang, which are home to plants that build Chinese nuclear arms and process plutonium for the weapons. It is not clear whether the plants suffered damage.
On Wednesday afternoon Chinese officials raised their estimate of the number of people killed to nearly 15,000. The latest figures put the number of people still buried at 26,000 and the missing at 14,000.
The deployment of a total of 100,000 members of security forces across the disaster zone, most from the People’s Liberation Army, is one of the largest peacetime mobilizations by any country in recent memory.
The soldiers marched through mud and debris to reach mountain towns at the epicenter on Wednesday while army helicopters began dropping food and medicine. On Thursday morning, high up in Beichuan, where the county seat had been flattened, workers brought rescue dogs to the ruins of a school where 1,000 children were believed buried. Bodies lay strewn throughout the town.
Hundreds of thousands of people remain homeless everywhere, and all across the region people are seeking shelter wherever they can find it, sleeping beneath plastic tarps, living in stadiums and lying on sidewalks.
The damage to dams and reservoirs is extensive. The People’s Daily, a state-run newspaper, reported that 51 reservoirs were “in danger” around the municipality of Chongqing, 170 miles east of Chengdu and closer to the gargantuan Three Gorges Dam. Hundreds of irrigation and water supply systems around Chongqing were damaged, amounting to an economic loss of $72 million.
There have been warnings that a serious breach of the Zipingpu Reservoir, which the soldiers were to inspect, could flood Dujiangyan, where hundreds of schoolchildren have been buried in rubble and where blocks of buildings have crashed to the ground.
The irrigation system there dates to the third century B.C., and Dujiangyan is close to the epicenter of the 7.9-magnitude quake that struck on Monday.
According to the official Xinhua News Agency, the earthquake “caused cracks on the surface of the dam of the Zipingpu Hydropower Station. Some walls of the plant and other buildings have collapsed, and some are partly sunk.”
Experts from China’s earthquake bureau raised concerns about the station’s location near a fault zone before it was built in 2000, according to Aviva Imhof, the China program director for the International Rivers Network, a group that opposed construction of the dam. She cited leaked transcripts of a September 2000 meeting about the issue.
The National Development and Reform Commission released a report on Wednesday saying that 391 reservoirs in five provinces had been damaged.
The nature of the damage is unclear, and so is the effect it might have on the lives of people in this mostly rural, mostly poor swath of China. Two reservoirs in the report are considered large, and 28 are midsize.
On Monday, Xinhua cited an executive with the China Three Gorges Project Corporation saying that the Three Gorges Dam, 350 miles east of the quake’s epicenter, had no damage.
J. David Rogers, a professor in the department of geological engineering at the Missouri University of Science and Technology in Rolla, said the Zipingpu station was a concrete-faced rockfill dam 512 feet high. That means it is not made fully of concrete. Rather, it has a surface of concrete that covers an interior structure of rock and earth.
Such a structure could be expected to have a “very noticeable” amount of settlement and cracking in a quake like this one, Dr. Rogers said. No matter what the damage is, he said, the first thing to do is to lower the level of water behind the wall, reducing the overall pressure that can cause further damage.
A dam can fail in slow motion, he said. “If they do have a leak, this thing could fail two weeks from now.”
One state news media report said late Wednesday that inspectors had declared the Zipingpu dam safe, while China National Radio said that soldiers would, in fact, release some water. A reporter for Caijing, a respected Chinese news magazine, wrote online Wednesday that he had seen cracks on the dam 10 centimeters wide and that workers had already drained the water to such a degree that parts of the reservoir bottom were visible.
Prime Minister Wen Jiabao was shown on state television Wednesday telling survivors that 100,000 soldiers, paramilitary troops and police officers would be involved in relief efforts.
For comparison, in 2005 the American federal and state governments dispatched about 50,000 members of the National Guard in eight days to areas ravaged by Hurricane Katrina.
The soldiers arriving at Wenchuan County, at the quake’s epicenter, began ferrying survivors across rivers on plastic skiffs. But in Yingxiu, the first township that the soldiers reached, only 2,300 of 10,000 residents could be confirmed alive, according to Xinhua. A poor farming region that is home to a famous panda reserve, Wenchuan is one of the worst-hit areas.
“There is an urgent need for medical staff, medicine, food and drinking water,” He Biao, the deputy secretary general of the prefectural government that includes Wenchuan, told Xinhua.
The fact that aid was able to reach Wenchuan was a minor triumph in the aftermath of the worst natural disaster to hit China in more than 30 years. Until Wednesday, Wenchuan had been completely cut off. Half of the survivors had severe injuries, Chinese officials said.
The threat of earthquakes and aftershocks remained high across the region. Tremors could be felt in Chengdu, the capital of Sichuan Province, on Wednesday and Thursday mornings.
The rains that had hampered aid efforts for two days let up on Wednesday, allowing easier travel and granting reprieve to cold survivors. The weather had forced the military to cancel rescue plans that included parachuting soldiers into Wenchuan and other hard-hit areas.
“Sichuan is so tremendously mountainous, it’s difficult to reach some of these areas even without an earthquake,” said Kate Janis, a program director at Mercy Corps, an aid organization that is preparing to send food, medicine and other supplies.
More than 800 police officers arrived in Yingxiu soon after 200 soldiers got through. Photos taken from a helicopter flying over a town in Wenchuan County showed empty avenues and rows of deserted buildings, and what appeared to be a cluster of makeshift tents on a soccer field.
Rocks and mudslides have cut off roads to the county, only a three-and-a-half-hour drive from Chengdu, and phone service has been wholly disrupted.
At 4 p.m. Wednesday, in nearby Hanwang Township, some 200 young soldiers marched toward a mountain range on the eastern flank of Wenchuan. As they reached the end of an undamaged road, they descended in two rows to a riverbed, then forded the muddy river. Their destination was Qingping, a village of 5,000 deep in the mountains.
It was still a 10-hour walk away.
Li Zhengxin, 17, a boy whose nearby hometown had been destroyed, watched the soldiers disappear around a bend in the deep ravine. “They are like our bodhisattvas,” he said, using the word for an enlightened Buddhist who helps others attain nirvana. “Now that they are here, our hearts feel more at ease.”
A photographer in Hanwang estimated that 70 to 80 percent of the structures had suffered damage, and about a tenth had been flattened. In the evening, cooking fires cast an eerie glow up and down the sidewalks. In Mianyang, where nearly 19,000 people are missing, there were reports of people waiting in line for three hours for a bowl of rice porridge.
The number of confirmed dead — 14,866 on Wednesday — is expected to increase by thousands or even tens of thousands as rescue workers reach more remote areas, but some rare moments of good news emerged on Wednesday. A woman who was eight months pregnant and trapped in rubble for 50 hours was pulled to safety in Dujiangyan, The Associated Press reported.
Safety officials were able to speak to the pregnant woman, Zhang Xiaoyan, while she was trapped, but rescue workers proceeded slowly for fear that the rubble above her would collapse.
“It is very moving,” said Sun Guoli, the fire chief of Chengdu. “It’s a miracle brought about by us all working together.”
Edward Wong reported from Chengdu, and John Schwartz from New York. Reporting was contributed by Andrew Jacobs from Beijing, Jake Hooker and Alan Chin from Hanwang, Gilles Sabrie from Beichuan, and Bill Broad from New York.