The Waikari River tsunami: New Zealand's largest historical tsunami event
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Date
2019-02-16
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Elsevier
Abstract
The Waikari River tsunami was caused by a landslide triggered by the 1931 Hawke's Bay earthquake, New Zealand's deadliest natural disaster to date. Although it was reported in newspapers and personal diaries at the time, this is the first study to examine the tsunami using a multi-proxy approach aimed at investigating the physical evidence of this event. Sedimentological, geochemical, chronological and microfossil analyses were carried out on an anomalous gravel layer within the sedimentary sequence of Waikari Station located in a meander bend close to the river mouth. The chronology was established by extrapolation from 137Cs data coupled with historical artefacts found within the gravel layer. Diatoms within the deposit were brackish, and most probably sourced from the adjacent tidally-influenced Waikari River. Principal component analysis performed on geochemical data showed that the anomalous gravel layer at all sites is associated with a cluster of elements not related to detrital input nor organic matter, but indicative of an estuarine source. A second, older, gravel layer was also identified. It is considered to have been deposited by an earlier tsunami, quite likely caused by a landslide generated by the 1863 Hawke's Bay earthquake. The deposit has similar sedimentological, geochemical and microfossil characteristics to the gravel layer deposited by the 1931 event.
This study adds valuable insights into the poorly understood topic of landslide generated tsunamis by investigating the largest historical event of its kind to occur in New Zealand. © 2019 Elsevier B.V.
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Keywords
Landslides, Earthquakes, Tsunamis, Geochemistry, Diatoms, New Zealand
Citation
Donaldson, G., Goff, J., Chagué, C., Gadd, P., & Fierro, D. (2019). The Waikari River tsunami: New Zealand's largest historical tsunami event. Sedimentary Geology, 383, 148-158. doi:10.1016/j.sedgeo.2019.02.006