Transportation impact assessment following a potential Alpine fault earthquake in New Zealand

Abstract

The Alpine Fault is the most major source of seismic hazard in the South Island of Aotearoa New Zealand, with the potential to produce a magnitude 8+ earthquake. It extends over 600 km in the South Island. There is a high probability of a rupture in the next 50 years, meaning that the next large earthquake on the Alpine Fault is likely to occur within our, or our children’s, lifetime. This is predicted to result in severe damage to the built environment, especially to infrastructure. To estimate how the road network might be affected by an Alpine Fault Magnitude 8 earthquake, this research developed a way to simulate post-disaster transportation impacts on a large regional road network. We used mean travel time, total travel time, total travelled distance as analysis tools. Our results show the significant increase in flow and total travel time on State Highway 1 between Marlborough and State Highway 7, and State Highway 6 connecting Nelson to Marlborough one day and one week after the impact. The trip analysis of one day, one week, six months, and beyond six months after the earthquake indicates that around 2.02%, 1.16%, 0.39%, and 0.13% of total trips, respectively, were unable to occur due to accessibility issues. Almost all the inter-district trips from the three main impacted districts (Buller, Westland, and Grey) were cancelled for at least one week after the earthquake. There are still ongoing operational performance issues. Trips that can occur typically face a significant increase in travelled distance and, consequently, travel time. The outputs from this model will provide emergency response and transportation organisations with critical information regarding the performance of the network following an Alpine Fault Magnitude 8 earthquake.