Sedimentary evidence of prehistoric distant‐source tsunamis in the Hawaiian Islands

Abstract

Over the past 200 years of written records, the Hawaiian Islands have experienced tens of tsunamis generated by earthquakes in the subduction zones of the Pacific ‘Ring of Fire’ (for example, Alaska–Aleutian, Kuril–Kamchatka, Chile and Japan). Mapping and dating anomalous beds of sand and silt deposited by tsunamis in low‐lying areas along Pacific coasts, even those distant from subduction zones, is critical for assessing tsunami hazard throughout the Pacific basin. This study searched for evidence of tsunami inundation using stratigraphic and sedimentological analyses of potential tsunami deposits beneath present and former Hawaiian wetlands, coastal lagoons, and river floodplains. Coastal wetland sites on the islands of Hawai΄i, Maui, O΄ahu and Kaua΄i were selected based on historical tsunami runup, numerical inundation modelling, proximity to sandy source sediments, degree of historical wetland disturbance, and breadth of prior geological and archaeological investigations. Sand beds containing marine calcareous sediment within peaty and/or muddy wetland deposits on the north and north‐eastern shores of Kaua΄i, O΄ahu and Hawai΄i were interpreted as tsunami deposits. At some sites, deposits of the 1946 and 1957 Aleutian tsunamis are analogues for deeper, older probable tsunami deposits. Radiocarbon‐based age models date sand beds from three sites to ca 700 to 500 cal yr bp, which overlaps ages for tsunami deposits in the eastern Aleutian Islands that record a local subduction zone earthquake. The overlapping modelled ages for tsunami deposits at the study sites support a plausible correlation with an eastern Aleutian earthquake source for a large prehistoric tsunami in the Hawaiian Islands.

A tsunamigenic delta collapse and its associated tsunami deposits in and around Lake Sils, Switzerland

“…Additionally, geochemical proxies such as Na, S, and Cl concentrations (e.g., Goff et al 2012;Szczuciński et al 2006) and/or biogenic contents are used to identify marine tsunami deposits; for example, pelagic and benthic fauna are used to infer tsunami deposits and their sediment source (e.g., Garrett et al 2015;Kitamura et al 2018;Smedile et al 2020;Szczuciński et al 2012;Tanigawa et al 2018). Terrestrial sedimentary records are used to infer minimum tsunami inundation (e.g., Chagué-Goff et al 2012;Moreira et al 2017) and run-up height (e.g., Bondevik et al 2005;Costa et al 2016;La Selle et al 2020;Paris et al 2020). Based on the internal structure, composition, and spatial distribution of tsunami deposits, it may be possible to estimate magnitude and flow conditions by tsunami inverse modeling (e.g., Jaffe and Gelfenbaum 2007;Jaffe et al 2012;Spiske et al 2010;Woodruff et al 2008).…”

Tsunami deposits: Present knowledge and future challenges

“…In Hawai‘i, the study by La Selle et al . () provided further support to a trans‐Pacific correlation between deposits detected on some Hawaiian Islands and an eastern Aleutian earthquake‐generated tsunami. This large prehistoric tsunami was dated in three sites on the Hawaiian Islands to ca 700 to 500 cal yr bp .…”

Offshore evidence of historic and prehistoric tsunamis on the north shore of Tutuila (American Samoa)

“…However, research carried out in the Hawaiian Islands has shown that the onshore deposits associated J o u r n a l P r e -p r o o f with the 1957 Aleutian tsunami are only a few cm thick at the most, despite runup heights over 10 m (Chagué-Goff et al, 2012;La Selle et al, 2020). While the thickness of tsunami deposits depends on a number of factors, including sediment availability, accommodation space and preservation potential (e.g., Dawson and Stewart, 2007;Szczuciński, 2020), it is likely that no deposit caused by the 1957 event was left behind in the Samoan Islands.…”