An earthquake measuring 5.1 on the Richter scale jolted a prefecture in northwest China's Qinghai Province Thursday morning, said the National Seismological Network of China. The quake struck the Mongolian-Tibetan Autonomous Prefecture of Haixi at 05:56 a.m. (Beijing Time). No immediate reports of casualties or damage are available. The epicenter was detected at 37.6 degrees north latitude and 95.8 degrees east longitude, with a depth of about 6 km.