Earthquake study into 'megathrust' risk off Hawke's Bay and East Coast

Scientists will start dropping 100 borrowed but especially-made seismometers into the ocean off the North Island coast next week to learn more about the earthquake and tsunami risks in the region.

The eastern coast has been under increased scrutiny as scientists warn of a potentially devastating "megathrust" earthquake which could release 2000 times more energy than the 2011 Christchurch earthquake that killed 185 people.

It will be New Zealand biggest use of seafloor earthquake recording instruments, with New Zealand scientists being joined by specialists from Japan, the US and the UK.

Focusing mainly on the more northern Hikurangi Subduction Zone, the seismometers will be dropped from Wairarapa to the East Cape.

After a recent confirence in Napier, GNS Scientist Dr Laura Wallace warned the area had "the potential to produce the world's largest earthquake and tsunamis".

Marcus Hayes-Jones, of the Napier Civil Defence, said he "can't emphasise how serious" New Zealand must take this "genuine risk".

The sinking of the Ocean Bottom Seismometers, on loan from Japan, will be done from NIWA research ship Tangaroa, and the equipment will be supplemented by 200 land-based instruments.

The project will record echoes from within the earth from both naturally-occurring earthquakes and from acoustic signals generated by US research ship the Marcus Langseth, which will be positioned off the coast, where what is regarded as possibly New Zealand's most active fault is believed to be capable of generating an earthquake up to magnitude 8.5.

GNZ New Zealand project leader Dr Stuart Henrys said the data will help understand why different areas of the Pacific and Australian tectonic plates boundary are behaving differently.

Some parts of the plates slide past each other in slow earthquakes while others appear to be stuck fast, possibly a catalyst for a huge earthquake in the future.

The more intensive study north off Gisborne promises to provide the best images seen anywhere in the world of a zone where slow earthquakes are known to occur regularly.