The faultline that caused New Zealand's deadliest earthquake runs closer to Bluff Hill and Napier's CBD than scientists previously thought.
The first detailed geological map of the Napier-Hastings urban area in 50 years, released this week by GNS Science, has placed the Awanui fault away from Te Awa and instead almost directly under the CBD it brought to its knees in 1931.
The fault partially ruptured at 10.47 am on 3 February, killing 256, injuring thousands and devastating the Hawke's Bay region.
"Our new analysis using the three-dimensional modelling places the Awanui Fault closer to Bluff Hill than we had previously thought," Julie Lee from GNS Science said.
"Under Napier, the 1931 fault movement did not reach the surface, making it what we call a blind or concealed fault, not visible at the surface.
"The new location doesn't change how Napier would be affected by any earthquake on the fault, because it runs so deep – but the new information will allow Hawke's Bay councils to make informed decisions about the future."
The map will be followed by a 3D model and a map of landforms.
Three-dimensional modelling helped GNS experts to better define the geological make-up of the area – including the extent of rocks such as limestone, and faults in the region.
"People living in Hawke's Bay need access to the best possible information about the ground beneath their feet, and we are sure this new map will help inform future decisions about development, land use and hazard management," Lee said.
Maps that forecast the probability of earthquake-induced landslides have also been released.
The forecast maps show the probability of a landslide coming from a given location, based on a range of earthquake and ground shaking intensities.
These can be used to identify areas which may be prone to rock fall and cliff collapse.
These forecasts along with the new geology maps will be loaded into the Hawke's Bay Hazard Portal.
"New Zealand's beautiful landscape comes with hazards like earthquakes, tsunami and landslides – and Napier-Hastings is no exception," Hawke's Bay Civil Defence Emergency Management Group manager Ian Macdonald says.
"Working with scientific experts and the latest technology, we are building a full picture of what's underneath the surface of our region – so we can plan for a resilient, thriving future."