University of Otago Geology Seminar

When an earthquake occurs, it is essential to know as soon as possible if it is going to generate a tsunami to organise the emergency response. In the Southwest Pacific the multiple subduction zones (Hikurangi-Kermadec-Tonga, Puysegur and Vanuatu trench), have the potential to host large magnitude subduction earthquakes, which can trigger tsunamis. It is paramount to rapidly characterise such earthquakes to assess their tsunamigenic potential. In Aotearoa New Zealand, W-phase moment tensor inversion is used to obtain earthquake source information to use as input for tsunami simulations. The W-phase is long period low amplitude phase visible early on seismogram. It does not saturate with magnitude, making it better at quantifying Mw for the largest earthquakes. It also provides the centroid, rather than the hypocentre of an earthquake, allowing better estimation of the spatial distribution of shaking impacts.

The W-phase is known for characterisation of global earthquakes, providing stable solutions 30 within minutes after occurrence time. When used on a regional scale, challenges and limitations arise as less seismic records are available. The network configuration, seismic source representation and tectonic structure of the region could have a direct impact on the solutions and are worth investigating. This thesis explores the specificities and limitations of a regional W-phase inversion for rapid characterisation of tsunamigenic earthquakes in the Southwest Pacific.

This talk is taking place in person and will be available via Zoom, but not recorded https://bit.ly/otagogeology