Earthquake M4.7 off the coast of New Zealand happened today. New Zealand is in the Australia plate and is one of the most seismically active areas of the world. The Australia-Pacific plate boundary reaches from the south part of Macquarie Island towards the southern area Kermadec Island chain in the area of New Zealand.
There have been 15 M7.5+ earthquakes reported around New Zealand since 1900. The four biggest happened near the Macquarie Ridge, including M8.1 occurrence a short distance west of the plate boundary in 2004 and the M8.2 occurrence on the ridge itself in 1989. In 1931, the biggest earthquake that actually happened in New Zealand was the M7.8 Hawke’s Bay quake and 256 people died. The studies show that the faults’ strain collection indicate that the same events are possible to happen again.
It is not clear if any of the memorable M8+ quakes that were close to the plate boundary were under-thrusting occurrences on the plate interface, or were intraplate quakes. One of the biggest normal fault earthquakes (M8.1) happened south of Samoa and created a tsunami where 180 people died on September 29, 2009.
By Michele Enli
Photo by Cal OES – License