An earthquake measuring 6.4 on the Richter scale struck the remote Qinghai Province in northwest China at 9:52 am Friday, the China Earthquake Administration said, but no casualties have been reported. A total of 128 aftershocks had been registered by 11 am near the epicenter in the Da Qaidam (also known as Dachaidan) district in the Mongolian-Tibetan Autonomous Prefecture of Haixi, with the strongest measuring 5.3 magnitude that struck at 10:14, according to the Qinghai Provincial Seismological Network.

"So far, we have not received reports of casualties or house collapses," the provincial government said in a statement. "The governments of the province, the Haixi prefecture and Golmud City have sent staff to investigate," it said.

The epicenter, at 37.6 degrees north and 95.8 east, was about 140 km away from Delingha City, the capital of the Haixi prefecture, and about 160 km away from Golmud, another major city in Haixi, according to the China Earthquake Administration. The quake was strongly felt in both cities, the administration said.

The China Earthquake Administration, the National Disaster Reduction Committee and the Ministry of Civil Affairs have all sent staff to the quake-hit region for relief work. Da Qaidam is a sparsely populated district with an average altitude of 4,000 meters and about 16,000 people, including Mongolians, Tibetans, Muslim Hui and Han.

The district covers 34,000 square km and administers three townships. Da Qaidam, which literally means "a big salt lake" in Mongolian, is rich in mineral resources, with one of the largest lead-zinc mines in western China and several coal mines.

On Nov. 10 last year, a 6.3-magnitude quake struck Da Qaidam but did not cause casualties. The quake only toppled several huts and caused cracks in the walls of some mud houses. In April 2003, a 6.6-magnitude quake hit the same region but did not cause casualties, either, and only damaged old buildings.