Shifting ground

Preparing victims for cremation after the earthquake that struck Kathmandu in April. Picture: Daniel Berehulak

BY TIM THWAITES (BSc(Hons) 1974, Trinity College, Janet Clarke Hall)

David Norrish was getting ready for a costume party when the Earth moved. Resplendent in baggy green hippie pants and a tie-dye shirt, he was on the roof of his four-storey apartment building in Kathmandu, Nepal, when the first jolt sent him staggering. It was April 25, this year, and an earthquake had struck.

“Struck really was the right term for what the earthquake did,” says the University of Melbourne genetics researcher, now working with the Nepal Health Research Council.  

“There was no warning or gradual increase in intensity. One moment the world was sane and stable, and the next the whole building was shuddering back and forth. I stumbled and caught my balance, and my brain needed a few seconds to figure out what was happening and how I should feel about it. 

“All the earthquake training we had done was only relevant for being inside a building. I ended up just dropping down where I was and crouching in a ball in the centre of the roof. Right before I hit the ground I caught a glimpse of the city and this surreal image is burnt into my mind: a swarm of black rising. It was thousands of crows taking flight in a wave of panic.” 

When the shaking stopped, Norrish (BSc 2009, MSc 2011) grabbed a first aid kit from his apartment and rushed out into the street. “I bumped into a nurse friend of mine who was on her motorbike heading to the local hospital, and I gave her the first aid kit. She told me later that the hospital had been so under-resourced that that first aid kit, by being there at that time, ended up saving several lives.” 

David Norrish in Kathmandu.

He wore his party costume for the next few days, as he came to terms with a catastrophe that devastated the city and killed more than 8500 in the region. “Hundreds of thousands of people were left living in the scary uncertainty of a dying city, with no electricity or running water and rapidly dwindling access to food and transport,” he recalls. 

It’s a scene likely to become increasingly common, says Associate Professor Mark Quigley (PhD 2007), who has forged a worldwide reputation in earthquake science at the University of Canterbury in Christchurch. He will be returning to a specially created position at the University of Melbourne in October, adding significantly to a research area of growing importance in science and engineering. 

Earthquake damage to humans and infrastructure is on the increase as the world’s population grows and settles over more and more of the planet, he says. Researchers from the US Geological Survey predict that the number of earthquake-related deaths could more than double in the 21st century to 3.5 million. 

But it’s not urban areas such as Los Angeles and Tokyo where lives are most at risk. As populations centres in well-to-do nations, their infrastructure is relatively prepared to withstand any shock. The real problems are in the burgeoning, crowded cities of less developed countries. And living in Australia, seemingly one of the seismically quieter parts of the Earth’s surface, is no reason to be complacent. Two of Australia’s most recent earthquakes – at Tennant Creek in 1988 and Newcastle in 1989 – were of a magnitude similar to or larger than the recent Christchurch earthquakes. 

In New Zealand, Mark Quigley – aka Dr Quigs – and his partner Candice became caught up, literally, in the earthquakes of 2010 and 2011. Their house was in one of the most vulnerable areas, and the sandy soil underneath it erupted to the surface, in a process known as liquefaction, resulting in serious damage and the property’s eventual demolition. 

But the two earthquakes were very different propositions for Quigley, as geologist-participant. “On September 4, 2010, Christchurch hosted the perfect earthquake. Details of the rupture process were captured by a dense array of instruments. And the surface rupture itself was a sight to behold – a geologist’s dream. While there was some damage, no lives were lost. And we did as scientists should do. We conducted research, tested hypotheses, collaborated with colleagues, spoke to the media, gave public talks, published papers and told our story to the world. 

“On February 22, 2011, Christchurch hosted a much different seismic event. This one caused many deaths, unbelievable destruction and mass evacuations from the city. The science response has been different, sombre and more subdued. Some of the public has lost trust in our abilities. It was a difficult, but important, time to be an earth scientist.” 

In the aftermath, Quigley became a household name in New Zealand and worldwide. For months, he appeared almost nightly on New Zealand television as the voice of science and evidence-based information. Among other honours for his efforts, he was awarded the 2011 New Zealand Prime Minister’s Science Media Communication Prize and the 2014 Geological Society of America Public Service Award. 

Dr Mark Quigley.

“My shift to Melbourne is not surprising,” Quigley says. “It’s building recognition in the field and has a strong engineering school. Many of the world’s leading earthquake scientists live in intraplate settings. But that comes with a responsibility to tackle earthquake-related challenges that transcend regional boundaries, and with a particular focus on assisting nations with a higher seismic risk and lower science capacity.” 

One urgent need, he says, is information on where the greatest risks are, how resistant we need to make buildings, and where we should avoid construction altogether. And that information has to be solid enough to resist the pressure of inappropriate development in places where there may have been little sign of an earthquake for many years. 

“We need to work hard to plan and develop cities and infrastructure that are informed by geologic information,” he says. “The use of the geological record to understand the location, size, frequency and effects of past earthquakes for the purpose of reducing our vulnerability to future earthquakes is what underpins the fields of paleo-seismology and earthquake geology.

“For example, our research in New Zealand has demonstrated virtually all of the worst effects of the 2010-11 earthquake sequence had prehistoric geologic predecessors of similar severity and extent that could have been better incorporated into land use planning policy. This is the field in which my expertise lies and the work I will be continuing with vigour at the University of Melbourne.” 

At the University Mark Quigley will rejoin his PhD supervisor, Professor Mike Sandiford (BSc(Hons) 1978, PhD 1985), who holds the Chair of Geology in the School of Earth Sciences, and with whom he has worked previously, examining earthquakes and the formation of mountain ranges in central Australia and the Himalayas. 

Of all the tectonic
plates, says Sandiford, the Indo-Australian plate is moving the fastest and is the most highly stressed. This puts Australia among the areas most prone to intraplate earthquakes. One of those who knows most about Australia’s seismic activity, particularly with respect to the rest of the world, is Gary Gibson (BSc 1968), a principal research fellow in seismology and president of the Asian Seismology Commission. He has been contributing to the Global Seismic Hazard Assessment Program, which is bringing together historical seismic data from all over the world to create earthquake hazard maps. 

It’s not an easy task. Precise measurements of earthquakes go back less than a century – a mere blink of geological time, although techniques are being developed to gain indications of much earlier events. Earthquakes play out differently in different geological environments, Gibson says, so comparisons become difficult. “A magnitude-5 quake in Western Australia may be felt 400 kilometres away, but only 150 kilometres away in Victoria, given its softer, more absorbent rock.” 

While the maps are preliminary and constantly being updated, they show the areas of greatest earthquake hazard in Australia are the south-east and southwest corners of the country, as well as central Western Australia. Our complacency doesn’t help. In the past few years, several insurance industry executives have expressed concern at the lack of basic earthquake risk mitigation by business and government in Australia. That’s a situation that researchers in the School of Engineering and its associated Centre for Disaster Management and Public Safety, such as Associate Professors Helen Goldsworthy (PhD 1990) and Nelson Lam (PhD 1993) and Dr Elisa Lumantarna (BE(CivEng)(Hons) 2001, MEngSc 2004, PhD 2012), are trying to change. They are working on earthquake-resistant building design and the development and implementation of building codes that address the risk. 

Buildings can be engineered and retrofitted to resist earthquakes, Goldsworthy says. And we now know quite a lot about resistant materials and construction, from investigating the reaction of buildings to events such as Christchurch and also from the latest research work on damage-resistant technologies. Meanwhile, David Norrish has decided to stay on in Kathmandu as it gets back on its feet. 

“After a couple of months, things are only superficially back to normal,” he says. “The traffic’s back to full bore. But you can still see where the houses are damaged. And the tourists have completely emptied out of the country. That’s seriously affecting livelihoods.”

Earth’s fault lines put big cities at riskThe thin, solid skin or crust on which we live is only five to 70 kilometres thick, or about 1 per cent of the distance to Earth’s centre. But by the time you reach the mantle underneath, the temperature has risen to more than 600 degrees, and the material you are passing through is becoming plastic. By the outer core, it has become liquid. The Earth’s core is hot – about 6000 degrees at the latest estimate. 

The crust and upper mantle is broken into a jigsaw of moving tectonic plates. Their movement crushes them together, pulls them apart, and forces them to slide past each other. 

Some are pushed under neighbouring plates in a process known as subduction. 

These motions are jerky. The friction of huge tectonic plates pressing and rubbing against each other is immense. 

Along active plate boundary faults, such as the San Andreas Fault in California, the pressure builds up until it exceeds the strength of the fault and the earth slips rapidly, moving metres in a matter of seconds. In the case of Nepal’s recent earthquake it moved about three metres. 

That rupture causes an earthquake as it cascades along the fault until the friction becomes too great to overcome and the rupture is terminated. But that concentrates stress on the fault further down the line, which is why earthquakes along fault zones are likely to cluster. 

About 95 per cent of earthquakes occur at plate boundaries. The people most at risk live in these regions, particularly at the edges of the Pacific Ocean and across Asia, from central China, along the Himalayas and extending through Iran and Turkey into Europe. 

The cities where most death and damage is likely to occur are in developing countries – Islamabad, Tehran, Quito, Manila. But 5 per cent of earthquakes occur intraplate. These are the ones that affect Australia, and while neither as frequent nor typically as big as those at the plate boundaries, they can still be significant and destructive.