Hopes earthquake forecasting will improve after scientists collect fault line data from east coast subduction zone

Scientists have collected two years worth of data from New Zealand's most active fault line to better understand the earthquake and tsunami risk it poses.

GNS Science hopes the information from the Hikurangi Subduction Zone of the North Island's east coast could be used to link slow-slip earthquakes to seismic events. And the information may even help them better forecast quakes in the future.

A yellow sensor has been sitting at the bottom of the ocean collecting data from the Hikurangi Subduction Zone. It's been recording slow-slip earthquakes, which can last for weeks on end.

Scientists from New Zealand, Canada, and the United States have spent 16 days retrieving equipment from the seafloor that has been recording changes in the Earth's crust for two years.

"The crust is sort of contracting or expanding in response to these slow slip events," says Laura Wallace, GNS geophysicist.

"Maybe one day in the future we might be able to use these slow earthquakes in doing better earthquake forecasting."

It could forecast quakes like the 7.3 magnitude one which struck off the east coast on March 5.

Their voyage couldn't have come at a better time because it set sail just four days after that earthquake hit.

"If we didn't have this cruise now the next opportunity to download that record will be in 2023," says Professor Evan Solomon, marine geochemist and geologist at the University of Washington.

That's because they need a remotely operated vehicle to retrieve the data, so ROPOS had to be shipped from Canada to do the job.

This is the first time ROPOS has been used in New Zealand, but it didn't come alone, it came with eight technicians and 60 tonnes worth of gear that will all be packed up and shipped back to Canada in the coming weeks.

Much of the data will be sent back to the United States to be analysed.

"We collected a record number of samples; we got 17,000 samples to analyse," Professor Solomon says.

The samples will take up to nine months to analyse and could provide a better picture of the link between the slow slip earthquakes on the sea-floor and seismic events like the earthquake three weeks ago.