Faults in New Zealand’s common greywacke rocks, which have caused devastation in Christchurch, Kaikoura and Edgecumbe in recent years, are for the first time being studied, backed by Earthquake Commission (EQC) funding.

Victoria University of Wellington researcher Carolyn Boulton says the country’s most common rock type has been neglected by scientists because it is “not colourful and rather tortured,” and she is passionate about correcting this knowledge gap.

“It’s in an awkward stage between rather simple sedimentary rocks and the shiny schist that blankets Otago,” Dr Boulton said.

EQC-funding has enabled Dr Boulton to look specifically at how greywacke rocks behave before, during and after earthquakes and how faults can communicate with each other.

“The results provide essential input data to build a simulated fault network to explain how faults interact and why New Zealand has multi-fault earthquakes,” Dr Balfour said.

The research team tested greywacke samples at Utrecht University in the Netherlands, which has apparatus that can measure the frictional properties of the rock at high temperatures and pressure, to quantify the properties of a fault and distinguish them from each other, “like different types of cars or bicycles”.

“Not all faults are the same,” says Dr Boulton.

The researchers built a physics-based model to calculate the temperatures underneath Wellington, allowing them to determine where seismic events are most likely to occur, and why.

The results will generate a better understanding of New Zealand’s insurance risk and inform hazard modelling and building standards.