The quake struck at 5:23 am (2123 GMT Sunday) 142 kilometers (88 miles) south-southeast of the city of Qamdo at a depth of 50 kilometres, the USGS said.
The China Earthquake Networks Center measured the quake as 6.1 magnitude at a relatively shallow 10 kilometers, the official Xinhua news agency reported, while the Hong Kong Observatory registered it as 5.9.
The USGS said the population of the region, which borders northeast India, mostly lived in buildings that were highly vulnerable to earthquake shaking but estimated there was a low likelihood of casualties and damage from the tremor.
Much of western China is prone to earthquakes.
Twin 5.6 and 5.9 magnitude quakes killed at least 95 people in Gansu province in July.
A magnitude 6.6 earthquake in Sichuan province killed about 200 people earlier this year, five years after almost 90,000 people were killed by a huge tremor in the same province.