Highly sensitive seismometers are being placed off the east coast of New Zealand to measure slow underwater earthquakes.
Scientists from New Zealand, Japan and the United States will spend 10 days deploying the instruments from the RV Tangaroa, a NIWA research ship, east of Gisborne.
The instruments will remain on the seabed for about a year.
Geological and Nuclear Sciences said slow earthquakes occur over weeks and months as a result of the Pacific and Australian tectonic plates meeting.
Marine geo-science head Vaughan Stagpoole said the instruments will give a full picture of what is happening underwater for the first time. Until now, research has come from instruments on land.
The ship sailed on Saturday.