New Zealand geologists have found evidence of large ‘megathrust’ subduction earthquakes beneath central New Zealand.
The scientist found proof that two huge earthquakes that ruptured in the southern part of the Hikurangi Margin in the past 1000 years.
The margin marks the collision zone between the Pacific and Australian tectonic plates and this evidence suggests that the boundary, located under the Cook Strait-Marlborough area, could rupture in large earthquakes.
A subduction earth quake is when earthquakes occur on the underside of the upper plate, where the two plates meet, rather than along faultlines within the upper plate.
They are responsible for some of the biggest quakes – and tsunamis – in the world, including the recent magnitude 9.0 Tohoku earthquake and tsunami in Japan in March 2011, and the magnitude 9.3 Indian Ocean earthquake and tsunami in December 2004.
Subduction earthquakes have the potential to be significantly larger in magnitude than upper plate fault ruptures, affect a much larger area, and are much more likely to trigger tsunami.