Rapid Earthquake Rupture Characterisation for New Zealand Using the FinDer Algorithm

Abstract

For large and damaging earthquakes, rupture location and extent are critical inputs for impact forecasts and response decision-making. This information has the potential to significantly improve estimates of ground shaking, as well as subsequent estimates of impact or loss, or secondary hazards such as landslides and tsunami. The R-CET programme (Rapid Characterisation of Earthquake and Tsunami) is implementing and testing a set of near real-time tools for use in event response, aiming to reduce the time taken to determine these critical input parameters from days or hours, to minutes or seconds. One of these tools is FinDer, the Finite-fault Rupture Detector, which aims to characterise the extent, location and orientation of rupture in the seconds to minutes following an earthquake, by matching spatial distributions of high-frequency seismic amplitudes with pre-computed templates. During real-time, and systematic and historic offline testing we have found that FinDer performs reliably in the New Zealand setting for onshore crustal earthquakes, providing reasonable magnitude and location estimates for M6+ earthquakes, and also strike estimates for M7+ events. FinDer was also created, and is used elsewhere, as an earthquake early warning algorithm, and while neither the national GeoNet seismic network nor the New Zealand FinDer configuration are currently designed for EEW, we can begin to test its capability and performance. We present a summary of the testing and performance of FinDer for New Zealand, and the opportunities and challenges it offers for earthquake response.