An international team of scientists set sail from Wellington on Saturday to lay an offshore network of seismic sensors on the ocean floor to give a better understanding of earthquake and tsunami risk from New Zealand’s largest and most active fault, the Hikurangi Subduction Zone. 

In research funded by Toka Tu Ake EQC, the sensors will detect earthquakes that are too small or far offshore to be recorded by the onshore GeoNet network. Victoria University of Wellington Professor Martha Savage says researchers are currently “effectively blind” to small earthquakes occurring offshore. 

“This is the first study to look for earthquakes on the locked part of the fault,” she said. 

“We’re expecting to see 10 times more earthquakes on the locked zone than are currently reported. The behaviour of these more frequent small earthquakes can tell us more about the larger earthquakes that occur less often.”  

The Hikurangi Subduction Zone is a plate boundary fault where the Pacific tectonic plate dives down westward beneath the Australian tectonic plate. It runs the length of the east coast of North Island. 

In places, the two tectonic plates are slowly sliding past each other, regularly releasing some of the accumulated pressure, but in other places they are locked together, stuck and building up pressure which could be released as a major earthquake. 

The Canadian Foundation for Innovation and the University of Ottawa also contributed to funding. Information carried by the seismic waves can also help better understand the likelihood of earthquakes, and how the movement of a future earthquake might cause a tsunami, University of Ottawa Professor Pascal Audet says.  

EQC Head of Research Natalie Balfour says the project could have significant benefits for New Zealanders. 

“If we better understand the locked portion of the fault and the smaller earthquakes that occur, it will help us prepare for the impacts of a large earthquake and potential tsunami should the fault come unstuck,” Ms Balfour said.