The likelihood, potential impacts, and risks of earthquake hazards were the focus of recent independent assessments by Tonkin + Taylor Ltd.

Otago Regional Council Senior Natural Hazards Analyst Tim van Woerden says “We were seeking more information to understand the earthquake hazards occurring for events of different magnitudes, the types and severity of damage these hazards could cause, and what secondary hazards could be triggered – such as changes to flooding risk.”

One assessment specifically looked at potential vulnerability to liquefaction impacts, finding that properties on the Clutha Delta could also be affected by this in a large earthquake due to the soft sediments making up the ground.

“The risk assessment looked at three different earthquake scenarios and found in the largest case of a ‘rare’ Magnitude 7 earthquake centred near the Clutha Delta, the area could be widely affected by severe ground shaking, and extensive liquefaction and ground deformation. While this scenario had the most severe impacts, it’s also the lowest likelihood of occurring with a less than 0.04% chance of occurrence in any year.”
In the ‘likely’ scenario, with a 1% chance of occurrence in any year, light to moderate ground shaking would be experienced at the Clutha Delta and would have only minor impacts.

“These studies help to give us a better understanding of the seismic hazards and risk in the area and feeds into the Clutha Delta Natural Hazards Adaptation work which seeks to better understand future hazards, collaborate with the community to decide what’s important, and build resilience.”

Earthquake scenarios and potential impact at the Clutha Delta