Skip to content

The threat of volcanic tsunami from Whakaari/White Island to the Bay of Plenty, New Zealand.

Craig Miller1, Stuart Mead2, Xiaoming Wang1, William Power1, Rebecca Fitzgerald1

Abstract

Near shore volcanoes pose difficulties to quantify threats to nearby coastlines from a variety of tsunami generation mechanisms.  Here we focus on flank collapse induced tsunami from Whakaari/White Island, New Zealand, and its impact on the Bay of Plenty coast.  We characterise the island through multi-physics geophysical inversion and clustering algorithms to identify saturated and hydrothermally altered rock volumes that are mechanically weak.  From these models we identify clusters of potential slope failures with differing characteristic safety factors and failure volumes.  Several areas are identified on the northwest and southwest flanks, and range in volume from 105 to 108 m3.  Characteristic volumes of rock are defined and used as sources for landslide stability models that feed into a widely used tsunami simulation code - COMCOT (Cornell Multi-grid Coupled Tsunami) for coupled landslide-tsunami simulations.   We adapted COMCOT specifically to handle debris flows typical of edifice failures so that we can fully couple the subaerial and submarine dynamics.  This involves a flexible nested grid algorithm that allows for two-way coupling of landslide-tsunami simulations to address differences in spatial resolution requirements and model coverages between landslide and tsunami simulations.  We model the tsunami wave height and inundation at the Bay of Plenty coast, about 50+ km distant and find that tsunami generated by flank collapse are highly directional yet can attain heights that create land threats for affected areas.  This work forms the basis of the first volcanic-sourced tsunami assessment for near shore New Zealand volcanoes.