The quake's epicentre was 156 kilometres south-south-west of Kokopo in East New Britain province.
It was in the same area as last week's 6.6-magnitude quake.
The USGS reports that tsunami waves of up to one metre are possible for coastal areas of PNG and up to 30 centimetres for coastal areas of the Solomon Islands.
Dellie Minding, a receptionist at the Rabaul Hotel in the east of New Britain, told Reuters news agency the earthquake had been felt, with many guests running outside, but there had been no damage.
At the Rapopo Plantation Resort on the coast, receptionist May Dovon said she had not heard of any casualties or damage, the agency adds.
"We felt the earthquake, everything was moving so we went out of the building," the receptionist told Reuters. "Nothing was damaged."
The country is still recovering from a magnitude 7.5 quake on 26 February.
At least 100 people died in Enga province, where massive landslides buried whole villages.
It took weeks to establish the full extent of damage in the remote, worst-affected areas.