The earthquakes occurring in the Autonomous Region of Bougainville is caused by the Solomon and Pacific plate tectonic movements.
This was revealed by the Port Moresby Geophysical Observatory.
A warning has been issued to people in the coastal areas, to take precautions, as more earthquakes are expected.
Bougainville has been experiencing earthquake activities recent weeks.
A huge earthquake shook last Friday, measuring 7.1 that occurred at the Eastern Solomon Sea. It affected areas in Buin, South Bougainville.
Another shock occurred, yesterday morning, measuring 6.9; the latest last night at 1127; measuring 7.5 on Richter scale.
According to Port Moresby Geophysical Observatory Assistant Director Chris McKee the earthquakes is caused by the Solomon and Pacific plate tectonic movements.
People living in coastal areas, are urged to take precautions, as more earthquakes might be expected.
A tsunami warning was cancelled today, after reports indicated Torokina in South West Bougainville experienced sea swells.
Principal Engineering Seismologist, Mathew Moihoi said data is directly generated to their support system through Telikom PNG network.
Currently the Buka system has malfunctioned.
The observatory office says it is sensitive when it comes to disseminating warnings to ensure unnecessary confusion or fear.