An earthquake measuring 4.9 on the Richter scale jolted Ngari prefecture of southwest China\'s Tibet Autonomous Region at 11:51 a.m. Thursday (Beijing Time), according to the China Earthquake Networks Center. The epicenter, with a depth of 10 km, was monitored at about 31.7degrees north latitude and 83.8 degrees east longitude, the center said in a statement. While the U.S. Geological Survey said an earthquake measuring 5.1 on the Richter scale jolted western Tibet at 11:50 Beijing Time Thursday.