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Source: GNS Science

The Northeast Japan megathrust and the southern part of the Hikurangi subduction zone have similar structural characteristics and the new work will compare their properties to shed light on the types of earthquake that might be expected from the Hikurangi subduction fault in the future.

The project will be led by earthquake scientist Brook Tozer, who has been awarded a two-year Rutherford Foundation postdoctoral fellowship to focus on the research.

However, one natural analogue to Hikurangi may be the subduction fault that produced the 2011 magnitude 9 Tohoku earthquake. 

Dr Brook Tozer

Dr Tozer will analyse detailed seismic recordings of the two subduction zones looking for clues that might point to future quake behaviour of the Hikurangi subduction zone.

“Megathrust faults produce the largest earthquakes on Earth. Seafloor movement associated with these events can also produce tsunamis, making them one of the most devastating of natural hazards,” he said.

These faults form where two tectonic plates converge and one plate dives down (subducts) beneath the other.

“Understanding the potential magnitude of earthquakes along the Hikurangi megathrust is critical for earthquake risk assessment in New Zealand.”

Earthquake magnitude is mainly controlled by the area of the fault that ruptures during an earthquake and how much movement (slip) occurs.

This ambitious project will analyse more than two-decades of seismic data records to address key questions about how the structure of the subduction zone impacts earthquake activity

Dr Dan Bassett

Estimates of these parameters for future Hikurangi megathrust earthquakes are currently not well defined owing to a lack of earthquakes in historical times.

“However, one natural analogue to Hikurangi may be the subduction fault that produced the 2011 magnitude 9 Tohoku earthquake.  

“Addressing this question requires a detailed comparison of the rock types, their physical properties, and relationships with observed fault slip behaviour.”

By analysing seismic waves that have travelled through the Earth’s crust, Dr Tozer will produce high-resolution 3D models of the subsurface structure of each region similar to a medical CAT scan.  

“Outcomes from this project will include improving our ability to assess the hazard posed here in New Zealand, as well as our understanding of megathrust faults globally.”

Dr Tozer grew up in Whanganui and has been studying and working overseas as a geophysicist for the past seven years. Most recently he has been based at Scripps Institution of Oceanography in San Diego, one of the world’s oldest and largest centres for ocean and Earth science research.

Dr Tozer’s supervisor at GNS Science, Dan Bassett, said Dr Tozer’s project will make a valuable contribution to the understanding of earthquake hazards in New Zealand and Japan.

“This ambitious project will analyse more than two-decades of seismic data records to address key questions about how the structure of the subduction zone impacts earthquake activity,” Dr Bassett said.

 The Fellowships are administered by the Royal Society and enable recipients to undertake full-time research for two years within New Zealand. Fellows receive an annual stipend plus additional funding to cover research costs.

Dr Brook Tozer

MIL OSI