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Improving Rapid Earthquake Characterization for Tsunami Early Warning for Aotearoa New Zealand and the Southwest Pacific

Description: 

Aotearoa New Zealand, located in the Southwest Pacific Ocean, is vulnerable to tsunamis. The Rapid Characterization of Earthquakes and Tsunami (RCET) project, led by GNS Science (Geological and Nuclear Sciences), aims to improve rapid analysis of large local and regional earthquakes to determine their tsunamigenic potential and better capture the rupture process. To this end, we are focusing on refining a W-phase solution (automated moment tensor inversions) on a regional scale. Unlike simpler automated magnitude determinations routinely used to analyze earthquakes in Aotearoa New Zealand, the W-phase does not saturate with magnitude, making it better at quantifying Mw for the largest earthquakes. It also provides the centroid, rather than the hypocenterre of an earthquake, allowing better estimation of the spatial distribution of shaking impacts. For these reasons we are developing synthetic earthquake waveforms to refine W-phase inversions for Mw ~5+ earthquakes in New Zealand and Mw 6.5+ earthquakes in the southwest Pacific, including the Hikurangi-Kermadec subduction zone. The current tsunami early warning procedure calculates W-phase solutions within 20 minutes of earthquake origins with aim of reducing it to 5-10 minutes.

Using a large set of large magnitude events adapted to New Zealand and Hikurangi-Kermadec context, we refine our understanding of the limits regional W-phase inversion. We focus on the minimum magnitude we can accurately estimate, the minimal station coverage required and the complexity of the source that can be apprehended by the W-phase.

We simulate earthquake waveforms using a catalog of synthetic ruptures on the Hikurangi-Kermadec subduction zone. To generate the waveforms, we use SPECFEM3D Globe, a finite element method-based software that simulates wave propagation through a global velocity model of the Earth. These synthetic waveforms are then postprocessed and inverted to obtain a W-phase solution. Preliminary results define which minimum waveform resolution is required to observe a W-phase and that a simple centroid moment tensor source provides an adequate W-phase solution.

Session: Creating Actionable Earthquake Information Products - I

Type: Oral

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Luce

Student Presenter: Yes

Invited Presentation: Yes

Authors