US research ship Marcus Langseth has spent five weeks studying the Hikurangi plate boundary off the East Coast of New Zealand.
Known as a subduction zone, it can develop a fault line is responsible for the largest earthquakes and tsunamis in the world.
These scientists have been studying the mystery of slow slips off the Gisborne coast.
"Slow slip earthquakes are characteristic of this north Hikurangi subduction zone and some others around the world and what we don't really understand is why some earthquake faults get stuck and produce big earthquakes while other earthquake faults produce these slow slips," explains Harold Tobin, professor of Geophysics at the University of Wisconsin.
Using seismic images to a depth of 20km can help them understand more about how the Hikurangi plate moves.
"The Hikurangi subduction zone is an active one, that means there's always the risk of a big earthquake taking place on that subduction plate boundary or of a tsunami being caused, so New Zealanders's should certainly be vigilant and ready," says Tobin.
The Hikurangi plate boundary is where the Australian and Pacific plates push against each other, creating a deep oceanic trench.
"So what our communities actually know what to do, for instance, if we feel a really strong earthquake or a long earthquake, we know because of the risk of passed events and what the scientists are learning that we need to evacuate really quickly," says Lisa Pearse, Chairman East Coast LAB
The Marcus Langseth is owned by the US National Science Foundation and is operated by the Lamont-Doherty Earth Observatory of Columbia University in New York.