28 Meter Tsunami Threatens New Zealand
- Michael Cunningham/Northern Advocate via AP.
In the new study, published November 29, in the journal JGR Solid Earth, the researchers created a catalog of 30,000 years of simulated time focused on the fault systems around New Zealand. The results revealed 2,585 earthquakes with magnitudes between 7.0 and 9.25.
The model suggests that the Hikurangi subduction zone is the most dangerous source of tsunami quakes near New Zealand, though the Tonga-Kermadec subduction zone north of North Island can also generate large, tsunami-causing quakes, just a bit further from shore.
The researchers were surprised to find that the tsunami hazard was caused by smaller, shallower faults called crustal faults, rather than the subduction faults themselves, Hughes said.
"Yes, the subduction zones are doing what we expect them to do. But our crustal faults also have a significant component of the hazard that we also need to account for," she remarked.
The team found the maximum height of a tsunami was 92 feet, which would result from a 9.13 magnitude earthquake about 394 miles (634 kilometers) northeast of Auckland in the South Pacific. The 2011 Tohoku tsunami in Japan was a 130-foot (40 meter) wave, for comparison.
The results suggest that New Zealand can expect a tsunami of 16.4 feet (5 m) approximately every 77 years, with a wave of at least 49.2 feet (15 m) approximately every 580 years.
Tsunamis over 3.3 feet (1 meter) high trigger land evacuations, Hughes said, while smaller waves can damage ports and harbors.
Though this is the first time the synthetic earthquake method has been used to study tsunamis, the same thing could be done for other at-risk places around the globe, Hughes said.
There is also more work needed to map out the risk to New Zealand, she added. The current study didn't take into account far-flung earthquakes around the Pacific, which can cause tsunami waves that resonate around the entire ocean.
"It is this huge step forward in risk assessment that we can now create a chain from what is creating the earthquakes, to what the earthquake looks like, and then what that looks like for the tsunami," Hughes said.
