Rare deep earthquake near Great Barrier Island
In the last 24 hours GeoNet detected a very deep magnitude 3.2 earthquake 15km north of Great Barrier Island from preliminary detection. The quake was registered at 12:06pm on 24 June and was only picked up by seismometers on the east side of the North Island possibly due to its depth or another far distant earthquake. The molten rock at that depth ‘dampens’ the energy from a deeper earthquake and may help to explain why the seismic energy is felt less near the epicentre when earthquakes occur in that area of the earth. When an earthquake happens in or near this slab of subducting plate, most of the quake’s energy travels up and along the slab to the surface - closer to the East and South of the North Island.
It’s only the 2nd very deep quake (below 300km) ever recorded in this location. The other quake at a depth of 750km was registered by GeoNet on 24 May 2013. Yesterday's deep quake is 30km east of the ongoing gulf swarm (109 quakes) which is also in the same location as the major New Zealand international communication cable and the Niagara shipwreck. The international communication cable carries 97% of New Zealand’s international communications. The Niagara ship was sunk on 19 June 1940 by a German marine mine and is still believed to be carrying up to 1000 to 1500 tonnes of oil and bars of gold.