A strong earthquake shook a border area between northern Thailand and Laos on Thursday morning, swaying Bangkok high-rises.

Residents in the northern Thai city of Chiang Mai felt a long period of shaking but saw no major damage. High-rise buildings swayed slowly for at least a half-minute in Bangkok, about 175 miles away from the epicenter, startling residents of the capital.

The U.S. Geological Survey said the 6.1-magnitude quake Thursday morning was about 6 miles below the surface. Moderate quakes of 4.6 and 5.7 magnitude shook the same area overnight.

The quake was centered about 19 miles from Chaloem Phra Kiat, an area about 15 miles from the border with Laos.