Off the North Island’s East Coast, the Pacific Plate dives under the Australian Plate in an area known as the Hikurangi subduction zone.
Such subduction zones have been responsible for extremely large earthquakes around the Pacific Ring of Fire, says GNS scientist Dr Stuart Henrys, so he and others are keen to understand the Hikurangi area in as much detail as possible.
GPS sensors revealed that in part of this zone, to the east of Gisborne, slow-slip earthquakes are occurring regularly – every two years or so. In slow-slip earthquakes, the movement is similar to a traditional earthquake, except it takes weeks to occur rather than seconds. The slip is so slow that no damaging shaking occurs.
Internationally there’s been a lot of scientific interest in slow-slip earthquakes, in part because they occurred in advance of the extremely destructive 9.1 magnitude Tohoku earthquake in Japan in 2011.
The slow-slip earthquakes observed off Gisborne are the shallowest in the world, so researchers from New Zealand, the US, the UK and Japan pooled resources to create a 3D map of part of this region in incredible detail.
Having crunched the data for many years, Stuart tells Claire Concannon about the surprising findings he and his colleagues have uncovered.
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