Scenario-based Modelling of Waves Generated by Sublacustrine Explosive
Eruptions at Lake Taupō, New Zealand
Abstract
Volcanogenic tsunami and wave hazard remains less understood than that
of other tsunami sources. Volcanoes can generate waves in a multitude of
ways, including subaqueous explosions. Recent events, including a highly
explosive eruption at Hunga Tonga-Hunga Ha’apai and subsequent tsunami
in January 2022, have reinforced the necessity to explore and quantify
volcanic tsunami sources. We utilise a non-hydrostatic multilayer
numerical method to simulate 20 scenarios of sublacustrine explosive
eruptions under Lake Taupō, New Zealand, across five locations and four
eruption sizes. Waves propagate around the entire lake within 15
minutes, and there is a minimum explosive size required to generate
significant waves (positive amplitudes incident on foreshore of
>1 m) from the impulsive displacement of water from the
eruption itself. This corresponds to a mass eruption rate of 5.8x10^7
kg s^-1, or VEI 5 equivalent. Inundation is mapped across five built
areas and becomes significant near shore when considering only the two
largest sizes, above VEI 5, which preferentially impact areas of
low-gradient run-up. In addition, novel hydrographic output is produced
showing the impact of incident waves on the Waikato river inlet draining
the lake, and is potentially useful for future structural impact
analysis. Waves generated from these explosive source types are highly
dispersive, resulting in hazard rapidly diminishing with distance from
the source. With improved computational efficiency, a probabilistic
study could be formulated and other, potentially more significant,
volcanic source mechanisms should be investigated.