As authorities in Papua New Guinea start to get a clearer picture of the scale of the destruction caused by February's magnitude-7.5 earthquake, there have been growing calls for the government to order a formal inquiry into what caused the quake.

Key points: Huge aftershocks and landslides have followed the February 26 earthquake

Huge aftershocks and landslides have followed the February 26 earthquake Australia has agreed to a request from PNG's Prime Minister to provide advice on the basis of the quake

Australia has agreed to a request from PNG's Prime Minister to provide advice on the basis of the quake The Governor of Hela province has called for an investigation to clear Exxon Mobil of suspicion

Aftershocks constantly rock already frightened communities, and many people are too afraid to return to their homes as landslides continue.

The exact death toll is unknown, but the number of reported deaths has climbed above 100.

Speculation is still rife among the affected communities that the quake was triggered by the activities of oil and gas companies in the region.

The biggest operation is the PNG LNG joint venture operated by Exxon Mobil PNG, which has gas production and processing facilities in Hela, Southern Highlands and Western Highlands provinces, all of which bore the brunt of the earthquake.

The Governor of Hela province, Philip Undialu, called for an investigation to clear Exxon Mobil PNG of suspicion.

Peter O'Neill (R) told the Post Courier newspaper there is no evidence oil and gas projects caused the tremors. ( Supplied )

Prime Minister Peter O'Neill told local media he had asked Australia's Federal Government to conduct an independent review of the cause of the earthquake, and had received an assurance the work would start soon.

Mr O'Neill told the Post Courier newspaper there was no evidence that oil and gas exploration and development projects had caused the earthquake.

He said it was an unusual event, although not unprecedented, and he knew people were concerned about what had caused the destruction.

A DFAT spokesperson said the Federal Government, through Geoscience Australia, had agreed to the request "to provide advice on the scientific basis of the earthquake and seismic activity in the region."

Geoscience Australia told the ABC in a statement that "the current national seismic hazard assessment indicates that the previous understanding of seismic hazard underestimated the level of risk."

It said PNG would have to investigate solutions including more rigorous building and construction standards, which would help communities stand up to potential future disasters.

The organisation already collaborates with the Port Moresby Geophysical Observatory on earthquake hazard assessment.

Women from Kekero painted white in mourning. ( ABC News: Eric Tlozek )

Australia boosts earthquake support

In the meantime, authorities are focusing on distributing aid to earthquake survivors who have fled to larger towns.

Disaster officials said the gatherings gave them a better idea of how many people were affected and what they needed, but also gave rise to concerns about sanitation and disease in the evacuation areas.

The Australian Defence Force increased its support at the request of Papua New Guinea government.

The C-17A Globemaster landed in Mount Hagen on Saturday. ( Department of Defence: CPL Oliver Carter )

An RAAF C-17 Globemaster loaded with humanitarian assistance and disaster relief supplies and ADF personnel flew to PNG from Townsville on Saturday.

Three Australian Army CH-47F Chinook helicopters are already in PNG helping to deliver emergency supplies.

"The current levels of ADF support, particularly the CH-47F helicopters and their ability to reach these remote Highland areas, is critical as the number of casualties rises and level of damage increases," Australia's Defence Minister Marise Payne said.

"The support provided by ADF personnel is enabling PNG Defence Force members to distribute critical humanitarian and medical supplies, including tarpaulins, bed mats and water containers."

The Australian government also said it had increased its humanitarian support to up to $1.2 million.

The quake and its aftershocks have caused widespread damage to infrastructure. ( Supplied: Catholic Bishop Donald Lippert )

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