Study: New Zealand at risk of tsunami waves as high as 92 feet every 580 years

A groundbreaking study conducted by a team of experts from Victoria University of Wellington has assessed the threat of colossal tsunamis facing New Zealand, revealing that waves as high as 92 feet may occur approximately once every 580 years. The study employed a novel approach using synthetic earthquakes and computer models that incorporated factors such as fault system geometry and physics, covering 30,000 simulated years to understand potential tsunami risks to both the North and South Islands of New Zealand.

The research holds significance due to New Zealand’s critical proximity to subduction zones, particularly the Hikurangi subduction zone, where the Pacific tectonic plate is beneath the Australian plate just offshore. Subduction zones are regions where two tectonic plates meet, and one is forced beneath the other into the Earth’s mantle.

Lead author Laura Hughes emphasized the urgency of comprehending the risks associated with these devastating waves due to the “really short timespan [between] when these earthquakes happened and when the tsunami waves hit.” The study, published in the journal JGR Solid Earth on November 29, identified the Hikurangi subduction zone as the most significant threat, although the Tonga-Kermadec subduction zone to the north can also generate sizable, tsunami-inducing earthquakes.

The study revealed that smaller, shallower crustal faults, rather than subduction faults, contribute significantly to the tsunami hazard. Results indicated a maximum tsunami height of 92 feet, with an estimated tsunami of 16.4 feet occurring approximately every 77 years and waves exceeding 49.2 feet happening roughly every 580 years.

While this study marks the first application of the synthetic earthquake method to study tsunamis, Laura Hughes suggested its potential use for assessing risks in other vulnerable regions globally. However, further work is needed to comprehensively map out the risk to New Zealand, as the current study did not account for distant earthquakes in the Pacific capable of generating tsunamis across the entire ocean.