'Short warning times': How a newly-discovered fault system poses risk to North Island

There's been a new fault system discovered off Gisborne and scientists have revealed what it might mean if a big one hits the region.

In a study published in the Bulletin of the Seismological Society of America, scientists determined the ages of marine terraces at two North Island sites - Puatai Beach and the Pakarae River mouth.

Scientists from GNS say "distinctive" marine terraces in the region were caused by earthquakes on multiple offshore faults, not by a rupture in New Zealand's active fault line - the Hikurangi subduction zone - as previously thought.

The newly-discovered faults are not far from the coastline and the result of that may be short warning times for a tsunami.

GNS says the study examines the growing understanding of seismological hazards along the East Coast.

"We need to learn more about these newly mapped offshore faults, how they might rupture together, and what they mean for the overall seismic hazard," said GNS' Dr Nicola Litchfield.

"Communities along the East Coast can do their part by following advice from the National Emergency Management Agency."

In November, GNS made some alarming predictions about what could happen if there is movement on the Hikurangi subduction zone.

It predicted there could be 1000 deaths, about 10,000 injuries and extensive destruction along the east coast of the North Island.

While the prediction was hypothetical and not designed to scaremonger, the scenario found up to 20 buildings would collapse in Gisborne, while landslides would cut off all highways.