The quake hit in eastern Myanmar, about 55 miles (89 km) north of Chiang Rai, Thailand, the survey reported.
It was a relatively shallow quake, which can be very destructive.
The Geological Survey initially said the quake had a depth of 142 miles (230km), but it later revised its estimate to say the quake was 6 miles (10 km) deep, putting it fairly close to the surface.
A second quake hit about half an hour later, with a preliminary magnitude of 4.8, the USGS said.
There were no immediate reports of damage or injuries.
The center of the quake was 589 km (365 miles) northeast of Rangoon, the capital of Myanmar, and 772 km (479 miles) north of Bangkok, Thailand.
It was 104 miles (168 km) south-southwest of Yunjinghong, Yunnan, China.
A destructive tsunami is not expected, the Pacific Tsunami Warning Center said. In advice to government agencies, the center said the quake "is located too far inland and too deep inside the earth to generate a tsunami in the Indian Ocean."
Myanmar, which is also known as Burma, has been badly hit by natural disasters in the past few years.
A powerful cyclone in 2008 left an estimated 100,000 people dead, and another one two years later left 70,000 people homeless, the United Nations estimates.
The quake was significantly less powerful than the one that hit Japan two weeks ago, causing a tsunami, leaving thousands dead or missing, and prompting fears of a nuclear meltdown.
It was roughly comparable in magnitude and depth to last year's Haiti earthquake, which measured 7.0. More than 200,000 people died in the Haiti earthquake, and millions were affected.
That quake's center was only 9 miles below the surface and near congested population centers. Scientists said if the quake had been centered deeper down, the damage would not have been as severe.