Beijing is unlikely to be further affected by a major earthquake that jolted Wenchuan County of southwest China's Sichuan Province on Monday, experts said.

Ding Lin, research fellow with the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences, said the large amount of energy released from the earthquake caused tremor in many parts of the country including Beijing.

Minutes after the Sichuan quake, at 2:35 p.m., a quake measuring 3.9 jolted Tongzhou District in east Beijing.

The quake was also felt in more than 10 provinces, autonomous regions and municipalities including eastern Shanghai, northwestern Ningxia and southwestern Yunnan and Chongqing.

"But further impact is unlikely to affect Beijing," said Ding, adding rumors that aftershocks with magnitude of 2-6 would occur in some parts of the capital was unfounded.

Zhang Guomin, a research fellow with the China Seismological Bureau (CSB), said it was an "internal earthquake" on the Chinese mainland and was a "shallow quake" with large destructive force.

According to Zhang, a shallow quake generally occurred above the depth of 30 km and a deep earthquake could reach a depth up to 650 km.

He added that 70 percent of earthquakes were shallow ones, which were a major disaster generator and the most devastating.

Statistics show quakes above the magnitude of 7 occur an average of 18 times each year and quakes measuring above 8 take place once or twice annually around the world.

He added that Wenchuan County was located in a seismic zone covering northwestern Ningxia and Gansu and southwestern Sichuan and Yunnan. It had a higher probability of having quakes.

An earthquake with the magnitude of 7.8 would cause house collapses, landslides and cracks in the ground.

"As all energy can not be released via a single quake, aftershocks would occur in regions surrounding Sichuan," he said.

He added that aftershocks were generally weaker than the main quake, but they would give rise to new disasters in nearby areas. He warned of immediate rolling stones, landslides, traffic congestions and ground damages.

Qu Guosheng, chief engineer of the China seismological emergency center, said a 30-member relief work team had already been sent to the area by the CSB's disaster relief department.

(Xinhua News Agency May 13, 2008)