Forecasting for a Fractured Land: A Case Study of the Communication and Use of Aftershock Forecasts from the 2016 Mw 7.8 Kaikōura Earthquake in Aotearoa New Zealand

Abstract

Operational earthquake forecasts (OEFs) are a way of looking at the probability of future earthquakes as time passes. These probabilities can be presented in a variety of formats, including tables, maps, and text‐based scenarios. In countries such as Aotearoa New Zealand, the U.S., and Japan, OEFs have been released by scientific organizations to agencies and the public. The intent is to provide information about future earthquake hazard and risk, so people can make informed decision. Despite questions about how useful OEF is for decision‐making, past earthquake events have shown that agencies and the public have indeed made use of such forecasts. Responses have included making decisions about safe access into buildings, cordoning, demolition safety, timing of infrastructure repair and rebuild, insurance, post-earthquake building standards, post-event land‐use planning, and public communication about aftershocks. To add to this body of knowledge, we undertook a survey to investigate how agencies and GNS Science staff used OEFs following the magnitude 7.8 Kaikōura earthquake in November 2016 in Aotearoa New Zealand. We found that agencies utilized OEFs in many of the ways listed above, and we document individual employee’s actions taken in their home‐life context. However, challenges remain regarding the interpretation of probabilistic information and applying this to practical decision‐making. We suggest that science agencies cannot expect non-technical users to understand and use forecasts without additional support. This might include developing audience‐relevant OEF information for communication purposes, alongside advice on how to use this information.