Sensing unrest in New Zealand’s largest city: detailed mapping of seismicity in Auckland

The Auckland Volcanic Field (AVF) presents a significant hazard to Auckland. More frequent earthquakes are a common precursor to volcanic activity globally, so it is expected that we would see this happen before volcanic activity in the AVF. This project sought to characterise the background seismicity in the AVF to enable detection of changes in earthquake activity that may be used to predict volcanic activity. Present knowledge of the background seismicity is limited by the GeoNet earthquake cataloguing workflow, and high levels of man-made seismic activity which make it difficult to detect small earthquakes using conventional sensors.

The project demonstrates that using a targeted approach to cataloguing earthquakes within the AVF was able to detect and located more than five times as many earthquakes as the GeoNet catalogue, however the rate of seismicity is still low compared to other volcanic regions in New Zealand. In doing so, the research showed that earthquake sequences occurred in the AVF without volcanic unrest.

To improve earthquake monitoring in urban settings, the authors tested detection applied to Distributed Acoustic Sensing data recorded on telecommunications fibre-optic cables, and concluded that this technology – while useful in providing more sensitive measurements – is best used in combination with conventional instruments to reduce false detections.