Australasian Science: Australia's authority on science since 1938

The Earth Moves

By Stephen Luntz

Prof Mike Sandiford is putting recent earthquakes, and human activities, into geological context.

Moe’s June earthquake shocked many Victorians, but Prof Mike Sandiford of the University of Melbourne’s School of Earth Sciences was relieved the event wasn’t larger.

“I grew up on the fault line,” Sandiford says. The Selwyn fault crosses the Mornington Peninsula from Cape Schanck to Dromana before running along the coastline to South Frankston, where it turns inland to the Dandenong Ranges. “We would hear earthquakes occasionally.”

The tremors inspired no desire to go into geology, but Sandiford says the fact he “walked 3 km through the bush to school each day” kept him interested in nature. “I was always on the water as a child, and my parents were agricultural scientists. I studied science at Melbourne University with no clear direction. I thought maybe biology, but I took a field trip to the McDonnell ranges and began to fall in love with trying to understand the history of where we live.”

For his PhD, also at Melbourne, Sandiford studied some of the oldest rocks on the planet – in Antarctica. “I was 100 km from base camp, which in turn was 300 km from Mawson. Most of the time I was with one other person, and a helicopter flew in to bring supplies and change who I was with. Occasionally it helped us move location. Mostly I was working on islands just off the coast, studying rocks that had been deep within the Earth – analogous to those in Tibet.”

Professionally, Sandiford has studied the evidence for large earthquakes revealed in the geology of south-eastern Australia, and found the Earth beneath our feet is not as stable as many think.

“The largest earthquake recorded in Victoria is 5.6. Moe was very similar , but there are fault ruptures visible that look like they were made by something close to 7.” These events have changed the Murray River’s course, throwing up obstacles including one that raised the land on one side by 5 metres over a 35 km length.

The legacy is the Barmah Forest, an internationally recognised wetland. “You can see the old path of the Murray before it was diverted around the obstacle,” Sandiford says.

Sandiford explains that the Indo-Australian plate is the fastest-moving plate carrying a continent, and the northward shift creates a high level of stress that is released through numerous small fault lines.

“We get a high 6 earthquake every 20 years or so somewhere within the continent. Land can be shifted 1–2 metres along an area 30 km long.” When a magnitude 5.6 quake occurred directly under Newcastle, 13 people died and $4 billion of damage was done.

Sandiford has drawn attention to the susceptibility of Australian cities to earthquakes, particularly Adelaide as the nearby Flinders Ranges are our most seismically active zone. However, he does not think that Australian cities lack appropriate building codes. “You could build Melbourne to withstand a magnitude 7 earthquake but it would cost trillions of dollars, and the probability is so low it is not worth it. We always live in the presence of risk and we need to balance the risk against the cost.”

Sandiford says that more earthquake-prone societies often lack the tools to manage their seismic dangers. He has studied heat flows and stress distribution along the boundaries of the Indo-Australian plate and trained Timorese scientists to seek evidence of past movements. “Another area I am working on is north of New Delhi, extending into western Nepal. In that area and immediately south live 100 million people. Nearby areas of the fault line have had magnitude 8 quakes, and this has not. We are trying to work out if it is overdue or if there is something about the area that enables the fault to move without big quakes.”

Sandiford heads the Melbourne Energy Institute (MEI), which brings together researchers, industry and community groups tackling the energy crisis. MEI is assessing the prospects for geothermal energy in Victoria, assisting Timor Leste in developing its renewable energy sector, and researching the prospects of powering Australia entirely from non-polluting sources.

“We dig 7.7 billion tonnes of coal each year to release 18 billion tonnes of CO2,” Sandiford says. “Our best estimate of how much sediment is produced by natural processes around the world is 10 billion tonnes. Humans have become a geological agent.” He believes these rarely noticed comparisons can increase understanding of our impact on the planet.

“The rate at which the planet loses energy through geological processes is 44 TW. At our current rate of growth we will be using that in 2060. If you look at the Himalayas you think the forces to create that must be vast, but they have been pushed up by 10 GW – about what Victoria uses on a hot afternoon.”