New GNS map of Hawke's Bay sheds light on quake information

Wednesday, 5 August 2020

A new geological map of Hawkes Bay released by GNS science will help councils plan for the risk of earthquake events.

A fault that ruptured during the 1931 earthquake is closer to Napier’s Bluff Hill than experts initially realised, a new GNS map shows.

The geological map of Hawke’s Bay is centred around the Napier-Hastings area, and included improved information about the Awanui Fault.

“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,” GNS geologist Julie Lee said.

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“Our new analysis using the three-dimensional modelling places the Awanui Fault closer to Bluff Hill than we had previously thought.”

Lee said the new location didn’t change how Napier would be affected by any earthquake on the fault, as it ran so deep, but the new information would allow Hawke’s Bay councils to make informed decisions about the future.

Three-dimensional modelling assisted GNS experts to better identify the geological make-up of the region, including the extent of rocks 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.

GNS Science also released maps forecasting the probability of earthquake-induced landslides across the region.

The forecasts, along with the new geology maps would be loaded into the Hawke’s Bay Hazard Portal.

The forecast maps showed the probability of a landslide, sourced from a given location and based on a range of earthquake ground shaking intensities.

The maps can be used to help identify areas that may be prone to rock falls and cliff collapse.

Hawke’s Bay Civil Defence Emergency Management Group Manager Ian Macdonald said while New Zealand’s landscape came with hazards such as earthquakes, tsunamis and landslides, Napier and Hastings was no exception.

“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.”