The danger is far from over in the mountainous terrain where last week's earthquake struck, with the risks of landslides, avalanches and flooding growing as the summer rainy season begins, Chinese officials said Thursday.
The warning came as the death toll from the May 12 quake rose to 55,239, with nearly 30,000 people still missing. More than 5 million are homeless and may not be able to rebuild their houses soon, or ever, because of the instability of the terrain.
"There will certainly be more landslides, new avalanches and mudflows," Yun Xiaosu, deputy land and resources minister, said at a news conference here. "We are still having aftershocks, and then next month is the start of the rainy season."
The grim assessment was based on high-resolution satellite photos provided this week by the U.S. government that show the potential for what are called "secondary geological disasters."
Quakes leave the ground fragile and susceptible to landslides. The biggest danger comes from "barrier lakes," which are formed when a landslide plugs a river and could easily overflow after a heavy rain or aftershocks.
Chinese geologists who examined the photos detected 34 such lakes. One particularly large one near the town of Beichuan already has forced the evacuation of thousands of people living in the potential flood path.
"These lakes pose a very severe risk," said Liu Yuan, an environmental official with the Land and Resources Ministry.
The satellite images were provided by the National Geospatial-Intelligence Agency, according to the U.S. Embassy in Beijing, along with medical and rescue equipment. Initial photographs were marred by heavy cloud cover, and the Chinese received another batch two days ago. The images also revealed damage to dams, reservoirs and hydroelectric plants.
The magnitude 7.9 quake rearranged Sichuan province's already complicated landscape of rushing rivers, flood-prone valleys and jagged mountains. Even re-creating roads is a dangerous mission. More than 200 government employees, most of them with the Transportation Ministry, were entombed in mud by landslides over the weekend when they tried to clear the rubble from a road near the epicenter in Wenchuan.
"The devastating phenomenon we see today is a natural consequence of the earthquake," said Guo Huadong, a geologist with the Chinese Academy of Sciences.
"Today's landslide will be the beautiful valley of tomorrow. Mountains are created this way. It is only unfortunate that this is a place where people live."
Guo, whose department reviewed the satellite images, said many areas would be left uninhabitable. Beichuan, where many of the 20,000 residents were killed, is in a steep valley squeezed between a river and mountain.
"Maybe they can build a memorial there to victims of the earthquake," he said. "But as far as living there, it is not a wise idea."
An appeal for tents
Housing the homeless is the next priority. The Chinese government appealed to the international community Thursday for 3.3 million tents, saying that only 400,000 had reached the disaster area. Officials said Chinese factories were working around the clock to produce tents but could not meet the demand.
The government also has set a goal of building 1 million temporary houses by August.
In addition to those people left homeless by the quake, many whose homes are intact have fled or are sleeping outside for fear of the aftershocks. About 20,000 are squeezed into a stadium in the city of Mianyang.
Times staff writer Mark Magnier in Chengdu contributed to this report.