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

摘要

The 2016 M-W 7.8 Kaikura earthquake involved complex rupture of multiple faults for 170km, generating strong ground shaking throughout the upper South Island leading to widespread landsliding. As a result of surface fault rupture and landslides, State Highway (SH) 1 and SH70 were blocked, isolating Kaikura and the surrounding communities, and necessitating evacuations by air and sea. In all these respects, the Kaikura 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 17 degrees and where peak ground acceleration was 0.43g, peak ground velocity was 41cm/s, or the modified Mercalli intensity was 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, SH73 near Arthur's Pass, and SH94 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 Kaikura earthquake is therefore necessary and likely to prove invaluable following an Alpine Fault earthquake.