An aftershock measuring 5.1 on the Richter scale jolted a prefecture in northwest China's Qinghai Province at 5:56 AM (Beijing time) on Wednesday, according to the national seismic network.

The epicenter was monitored in the Mongolian-Tibetan Autonomous Prefecture of Haixi, at 37.6 degrees north latitude and 95.9 degrees east longitude, about 10 km deep.

The aftershock lasted more than 10 seconds. Many residents rushed out and stayed outside till dawn. No casualties were reported.

Transportation, power and telecommunication facilities in the area remain unaffected.

The provincial Seismic network has monitored more than 800 aftershocks as of 8:00 AM on Wednesday.

A 6.3-magnitude quake hit the prefecture on Monday, leaving three minors slightly injured, at least 500 houses damaged and big cracks in many walls.

The direct economic loss is valued at 6 million yuan (about US$857,000), said an official with the administrative committee of the Da Qaidam District, the epicenter of the quake.

Da Qaidam is sparsely populated with about 16,000 people, including Mongolians, Tibetans, Muslim Hui and Han.

(Xinhua News Agency November 12, 2008)