ABSTRACT
The Lake Wanaka Rock Avalanche is a large translational rockslide (est. volume 5–10 × 106 m) near the head of Lake Wanaka in the Southern Alps. Failure occurred in the early postglacial era, on steep schist slopes weakened by toppling. The rock avalanche impacted the lake and a large tsunami is inferred. The trigger was likely a seismic event or extreme rainfall. There is a high probability of an Mw 8 earthquake on the nearby Alpine Fault (Australian-Pacific plate boundary) in the next 50 years. The quake is likely to trigger rapid “first-time” rockslides around the steep lakeshore, and the lakeside town of Wanaka is potentially at risk from any earthquake generated tsunami. The public needs to be informed of the risk, and advised to immediately move from shoreline areas to higher ground after a strong earthquake.
