Shortly before 6am this morning a 4.5 magnitude earthquake occurred at a depth of 5km, 15km southwest of Muswellbrook.
An initial earthquake (magnitude 4.8) on August 23 led the Nannas to ask “How dangerous are these quakes to gas infrastructure – especially pipelines?”
Our concern is that Santos wants to build the Hunter Gas Pipeline from their Narrabri Gas Project through this region to Newcastle. Since the initial earthquake there have been more than 20 aftershocks in the Muswellbrook region.
After the first earthquake the local MP Dan Rapacholi said, “While the damage has been fairly minor, some local homes and businesses have suffered structural issues, and the Council has been monitoring their assets for any damage, particularly to underground water pipes and dams.”
This map shows where the main seismic activity came from around 6am for the first earthquake. The Conversation did a lengthy piece on whether recent earthquakes in this region were caused by mining. “Overall, the available evidence for the recent earthquakes near Muswellbrook does not allow us to say unequivocally whether they are related to mining.” [1]
More than 39,000 kilometres of natural gas transmission pipelines are sprawled across Australia, three times the distance between the country and the North Pole. [2] Earthquakes can and do happen anywhere in Australia. Tectonic forces are still the main cause of moderate earthquakes in Australia.
The Hunter Mooki Thrust is the where the earth pushes against itself and causes seismic activity.
The Hunter Gas Pipeline from the Narrabri Gas Project will be nearly directly over this thrust line.
“The Australian Geological Survey Organisation in Canberra estimates that on average, the Australian region experiences an earthquake of size of the 1989 Newcastle quake every 13-15 months. Most of these earthquakes have been in low populated areas, so for many years people thought Australia could not be affected by this natural disaster. The Newcastle experience dispelled this myth!” [5]
The other higher hazard areas are in the region south from Gladstone towards the NSW border. [6]
Queensland’s 2024 State Earthquake Risk Assessment [6] sets out the following
Damage could happen to all power networks – wind, solar, hydro and gas. With gas it is the danger of fire and methane leakage which would be of most concern.
• Underground gas and oil pipelines traversing areas with seismic hazards (e.g. faults) have a moderate chance of rupture and low chance of complete breakage. The probability of rupture and breakage will depend on the precise nature of assets and the earthquake event.
• In-ground infrastructure exposed to earthquake shaking and those elements in the softer soils are more likely to be damaged than those in solid rock. Aged below ground gas and oil infrastructure such as pipelines (of non-polyethylene construction), wells and other infrastructure may be vulnerable to intense ground shaking leading to ruptures. Such ruptures may lead to disruption to services, contaminated drinking water and/or environmental damage. In some cases, buried pipelines are warped or broken by permanent ground deformation (ruptures) as seen below from a cluster of magnitude 6 earthquakes in Tennant Creek, Northern Territory in 1988. Pipes may also be warped or broken by shaking, liquefaction, lateral spreading, or landslides related to an earthquake.
• Domestic gas supply is likely to experience medium term disruption in the worst affected areas.
• Depending on the quantity of in-ground oil and gas storages, and ignition sources such as downed powerlines, there may be a high risk of fire with the releases of oil and gas from infrastructure and pipeline ruptures.
One of the main concerns is that “after an earthquake occurs, the location and severity of defects in the gas network may not be known immediately” [7].
Conclusion
There is evidence that earthquakes and seismic activity are risk factors to high pressure gas pipelines, but this is just one of the possible problems. Accidents such as natural gas leakage often occur due to third-party damage, corrosion, ground settlement, material failure, earthquakes, and other natural disasters during the operation of natural gas pipelines. [9]
Lock The Gate’s research found that “there are a range of causes of pipeline incidents. In the US, the causes of serious pipeline incidents during gas distribution, broken down by percentage, are: 4.2% corrosion; 26.3% excavation damage; 11.1% incorrect operation; 7.6% material/weld/equipment failure; 6.5% natural force damage (e.g Hurricane Katrina), 25.2% other outside force damage, and 19.1% all other causes. Safety risks are worse if pipelines aren’t frequently monitored and inspected.” [10]
(The Coalition has proposed to build a nuclear power plant in this region.)
References:
USGA Earthquake Hazards Program
Earthquake hits NSW Hunter Region weeks after two similar events (ABC News)
[2] https://www.australianmining.com.au/contending-with-unseen-hazards/
[4] https://www.maitlandmercury.com.au/story/4639703/construction-of-queensland-hunter-gas-pipeline-to-begin/
[5] https://www.cairns.qld.gov.au/__data/assets/pdf_file/0008/185930/EarthStoriesJ.pdf
[7] Earthquake Risk of Gas Pipelines in the Conterminous United States and Its Sources of Uncertainty https://ascelibrary.org/doi/10.1061/AJRUA6.0001202