Mover and shaker
A $200,000 science prize has gone to an extraordinarily young professor who lived through the Canterbury quakes and is helping predict the effects of future tremors.
Predicting the next earthquake is likely to remain impossible for some time, but Brendon Bradley, a civil engineer at the University of Canterbury, is working on the next best thing. Using detailed information about underground geological formations – from the stiffness of rocks to the softness of soils – he has developed models that forecast how different parts of New Zealand will be affected by shaking after a seismic tremor.
The research has earned Bradley the Prime Minister’s MacDiarmid Emerging Scientist Prize, worth $200,000, in recognition of his sophisticated seismic-hazard analysis and simulations of ground motion. At 30, he is one of the country’s youngest scientists to hold the position of professor. The deputy director of QuakeCoRE, a centre for earthquake resilience research, he has climbed the academic rungs from PhD to professor in six years, driven by his quest to better protect communities from earthquake damage.
Bradley’s vision is clear. He wants earthquake resilience to become a topic of public discussion, as relevant as healthcare and the economy. He credits this vision and his ability to harness advances in science to produce high-impact research for his fast career progression.
An interest in nature’s forces goes back to a childhood spent in Blenheim, but Bradley says, like most people, he didn’t choose a specific career path until he was into his first years at university. He has maintained a love of the outdoors throughout, however, and finds that some of his best ideas come during long runs in the mountains.
His goal is to identify buildings and infrastructural lifelines – hospitals, bridges, large office blocks – that are most at risk of earthquake damage but are of crucial importance to people, and to shift the emphasis of urban planning and building codes towards more robust designs. “We could do a really good job of making the few critically important buildings much more resilient, rather than our current approach, which is to do very little to most buildings and nothing
to some. The end result is that we’re not improving the resilience of our communities.”
Already, Bradley’s work is having an international influence, including on building-design codes. At home, he’s been involved in the redevelopment of Christchurch Hospital, the repair and extension of Lyttelton’s port, and the rebuild of the city’s sports facilities and central precincts.
“Most of the anchor projects in Christchurch are directly using the application of the research tools and results that we’ve obtained.”
DID THE EARTH MOVE FOR YOU?
Ground- motion models have been used to assess the risk of earthquake damage, but, traditionally, they relied on shaking observations. Bradley’s team is building models that use a region’s underlying geological data to simulate how seismic waves propagate across the landscape and what vibrations they cause for different building types.
The models were developed for Canterbury because the Christchurch earthquakes have prompted more investment in the collection of detailed geological information. The approach has substantially improved predictions of the impact of ground shaking, says Bradley. “As we understand better what happened and why, it allows us to extrapolate lessons to other areas of New Zealand, and even other parts of the world.”
Earthquakes produce seismic waves of different frequencies. Shorter, sharper jolts are most pronounced close to the fault, whereas longer, rolling waves travel further and can cause damage far from the source. The 7.8-magnitude Kaikoura earthquake last November taught us this lesson when it skipped 150km up the east coast of the South Island, setting off 21 separate faults in the process and releasing enough energy in Wellington to force the demolition of some of the capital’s most modern buildings.
Bradley says the properties of the ground in downtown Wellington meant that the shaking frequency matched the frequency of movement of buildings between seven and 15 storeys high. “These buildings will move a lot more because you’re shaking them at their predominant period, and resonance occurs,” he says.
Although every quake is different, the soil properties in a region remain the same. “If we can do a better job of modelling the local conditions, then we can characterise the specific nature of the shaking that any building is going to be subjected to.”
The question on many people’s minds is how the country will fare when the inevi- table big one hits. Bradley’s team has used the model to predict what would happen in Canterbury if the Alpine Fault were to rupture in a magnitude 8 earthquake, as it has done every 330 years, on average.
“The starting location of the earthquake [on the Alpine Fault] influences how great the shaking is in different parts of the South Island. If it starts in the middle, the shaking lasts only about half as long as it does if the earthquake starts in the north or south of the fault. If it starts in the north, the effect in Canterbury is pretty small. If it starts in the middle, the effect is quite large, and if it starts in the south, the effect is even greater – it just takes longer for the shaking to arrive in Canterbury.”
On a finer scale, Bradley’s models can predict the risk of damage to infrastructure. “The big problem is always this trade-off between something that is going to happen infrequently, such as the several hundred years between earthquakes, and the cost of fixing it now. One of the important things with these models is that they give substantially better understanding of the specific nature of the ground shaking, and once we can model the specific features, we can understand which buildings are going to be more impacted than others.”
Supercomputers are helping to revolutionise the research by completing calculations and video animations in a day that would take years on a laptop. And the detailed analysis is helping to find a better balance between resilience and economics. “Some buildings and infrastructure are too important to fail, so we have to make sure we mitigate the consequences of those suffering substantial damage and make them more resilient. It’s about investing more money where the risk is greater, investing less where the risk is lower, and taking into account the building function.”
When Bradley began his doctorate in 2007, he had no first-hand experience of earthquakes. Within two years of completing it, he had experienced both of the devastating Canterbury tremors and the 2011 magnitude-9 Tōhoku quake in Japan.
“As a researcher, I realised how important it is to experience large earthquakes: when you feel them, do reconnaissance after them and talk to people and understand the impact it has on them. It forces me to make sure the research I do is not just academic, but that it has immediate and short-term benefits in the way we build things and in the way we can reduce earthquake damage, or equally importantly, recover after we sustain earthquake damage.”
Bradley is on sabbatical at Stanford University in California to collaborate with other earthquake scientists. He says his time overseas has taught him that New Zealand is fortunate to have a high level of insurance cover to cope with the recent earthquakes, but could become vulnerable if it follows the example of California and Japan, where insurance cover has been reduced significantly.
He plans to spend the prize money on buying advanced instruments to investigate soil properties and to measure different wavelengths of shaking. He hopes the prize and support for resilience research will be comforting to people who have been affected by earthquakes.
“Some buildings and infrastructure are too important to fail, so we have to make them more resilient.”