Road impacts from the 2016 Kaikōura earthquake: an analogue for a future Alpine Fault earthquake?

Abstract

The 2016 Mw 7.8 Kaikōura earthquake involved complex rupture of multiple faults for > 170 km, generating strong ground shaking throughout the upper South Island leading to widespread landsliding. As a result of surface fault rupture and landslides, State Highway 1 and State Highway 70 were blocked, isolating Kaikōura and the surrounding communities and necessitating evacuations by air and sea. In all these respects the Kaikōura earthquake can be considered an analogue for a future Alpine Fault earthquake, providing lessons for the necessary emergency response. Landslide blockages primarily occurred where surrounding slopes averaged > 18° and where Peak Ground Acceleration was > 0.43 g, Peak Ground Velocity > 41 cm/s, or Modified Mercalli Intensity > 7.9. Using a potential future Alpine Fault scenario earthquake, this study identifies locations on other key state highway routes that have similar predictive variables that may therefore become blocked in a future earthquake. This suggests that SH6 between Hokitika and Haast, State Highway 73 near Arthur's Pass, and State Highway 94 south of Milford Sound are all likely to be affected. This will necessitate the evacuation of large numbers of spatially distributed tourists as well as the resupply of isolated local populations. The possibility of bad weather along with a lack of sea ports south of Hokitika will likely make such activities challenging. Contingency planning based on experiences from the Kaikōura earthquake is therefore necessary and likely to prove invaluable following an Alpine Fault earthquake.

Tercentenary of the 1717 AD Alpine Fault earthquake: advances in science and understanding hazards

“…The process of developing a robust, credible science scenario is presented, and current gaps in knowledge particularly in impact and consequence resilience science are described. Robinson (2018) describes the likely effects on the West Coast road network, and consequently on people and places, from landslides and surface fault rupture caused by a large Alpine Fault earthquake. An analogy is used of the Kaikōura earthquake road network disruption to demonstrate some of the societal consequences of a future Alpine Fault earthquake.…”