The paleotsunami record of the Auckland region and implications for understanding tsunami hazards

Abstract

The Auckland region does not have a historic record of significant tsunamis but modelling suggests the eastern coastline could be exposed to tsunamis from the Kermadec Trench with wave amplitudes of up to 10 m on Great Barrier Island/Aotea and 1-5 m on the mainland. Paleotsunami research could contribute to filling the disconnect between historic records and tsunami modelling by providing a tsunami record over a time span of thousands of years that is more likely to capture the long recurrence intervals of great subduction earthquakes at the Kermadec Trench. Here we review existing paleotsunami information and results of new field studies in the Auckland region (primarily on Great Barrier Island/Aotea). Three sites (Tāwharanui, Whangapoua Beach and Harataonga Bay) have strong evidence of Holocene paleotsunami but the dating of the inferred paleotsunamis at all sites is relatively poor. The coastline of Auckland and its neighbouring regions offer our most promising sites to better understand the size and frequency of large to great Kermadec Trench earthquakes and this information could be of critical importance for understanding tsunami risk in New Zealand.