"We felt it. It was swinging back and forth for a minute or two," Patrick Chan, a meteorologist at the US National Weather Service, said.
 
"It's not expected to cause a tsunami," the Guam-based meteorologist said.
 
The Pacific Tsunami Warning Centre, based in Hawaii, said in a statement that there was "no destructive widespread tsunami threat".
 
Neither Guam nor the Philippines have issued tsunami warnings.