Further work is being undertaken to understand active faults near Wānaka following a review completed in March this year.

A recent review of active faults in the Queenstown Lakes and Central Otago districts by GNS Science, commissioned by the Otago Regional Council (ORC), identified a likely active fault under Wānaka, which may be part of the North West Cardrona Fault.

This fault was previously thought to have run northeast from Cardrona Valley, through Albert Town to Hāwea. 

GNS scientists now propose that the fault runs northwest past the foot of Mount Alpha, beneath part of Wānaka township, and out under the lake.

ORC natural hazards analyst Ben Mackey said further work was needed to substantiate the findings and understand any implications for Wānaka.

“Since receiving the GNS report, the ORC has commissioned the National Institute of Water and Atmospheric Research (NIWA) to carry out a geophysical survey of sediments beneath Lake Wānaka. This work will look for evidence that the fault continues out into Roys Bay,” said Mackey. “The survey is taking place over two days beginning 2 December on Lake Wānaka, where they will focus their efforts from Roys Bay to Beacon Point.”

NIWA will be using advanced multibeam echo sonar equipment to map the lake, a process where systems emit sound waves in a fan shape beneath the boat's hull, gaining information from the returning soundwaves.

The goal of the survey is to improve ORC’s understanding of the active faults in the area and narrow down what hazard they may pose for Wānaka and the surrounding area.

“The lake sediments record past natural hazards, and in Lake Wānaka we are searching for disruption of sediment layers caused by surface or near-surface rupture of faults during earthquakes.” said NIWA marine geologist Dr Joshu Mountjoy. “In Wānaka we are looking for the lakeward continuation of a newly-mapped fault and we are hopeful that we will get a much better picture of what is happening.”

To read the full ‘Active Faults – Central Otago and Queenstown Lakes’  report, visit orc.govt.nz/otagofaultsreport [PDF].

For more information on how to prepare for an emergency, visit the Emergency Management Otago website: otagocdem.govt.nz.