A strong earthquake that killed three and shook up thousands of others yesterday morning in Yunnan was "no surprise" to seismological officials, who claimed the southwest province experiences 40 percent of the country's perceivable tremors.

Experts are working round the clock in the city of Pu'er after it was struck by a temblor with a magnitude of 6.4, trying to monitor any further serious seismic shifts, Huang Jianfa of the China Earthquake Administration told last night.

"Before the Sunday quake, the city and its vicinity had been jolted by nine earthquakes since 1970, with the magnitude ranging from 5.2 to 6.8 and causing 21 deaths," the director of the agency's earthquake emergency relief division said.

"We are assessing the destruction and keeping a close eye on the region to figure out if there will be stronger quakes."

The official said the Geneva-based United Nations Office for the Coordination of Humanitarian Affairs called his agency twice yesterday asking about the situation in Yunnan and whether China needed international aid.

"We informed the office about developments, and told them we could deal with the relief work ourselves."

Pu'er covers an area of 45,000 square km and has a population of nearly 2.6 million. It borders Vietnam, Laos and Myanmar.

The strongest and worst earthquake that hit Pu'er over the past three decades occurred on March 15, 1979, which claimed a dozen of lives and injured 563 others, according to Huang.

China has about one-third of the world's total terrestrial earthquakes, and Yunnan Province is the most earthquake prone - home to around 40 percent of all the quakes reported in the country, the official said.

"That's why we have listed Yunnan a priority observation and monitoring region, and have been doing research and analysis," Huang said.

"However, we - like in other countries - cannot make a reliable forecast of imminent earthquakes."

As aftershocks naturally follow a major quake, Huang warned residents to stay clear of their houses and guard against other possible natural disasters if there were heavy rains.

Chen Yuntai, deputy chief of the Seismological Society of China, added that earthquakes in mountainous areas could easily cause landslides and mudslides, which in addition to disrupting highways, would add to the casualties and make relief work harder.

(China Daily June 4, 2007)