The magnitude 6.7 quake hit just after midnight local time in the mountainous region around the border of Western and Hela provinces.
It's the same region where the epicentre of last week's powerful 7.5 quake was located.
Aid workers are still struggling to reach remote parts of this area where there is widespread damage.
Up to 150,000 people are believed to be in urgent need of emergency supplies.
Local media is reporting the death toll has grown to 75, after government officials previously said 55 people had been killed.