In search of Holocene trans-Pacific palaeotsunamis

There is a rapidly growing number of palaeotsunami sites being reported from the Pacific region but rarely have researchers looked far beyond their immediate site to find contemporary evidence at more distal locations. However, over the past 150 years the region has experienced giant earthquakes and their associated tsunamis from several key circum-Pacific sources. The 2011 To over bar hoku, 1960 Valdivia, 1946 Aleutian and 1868 Arica tsu-namis have been Pacific-wide events that, together with recent modelling, serve as a guide in helping to un-derstand those that occurred in prehistory. Extant palaeotsunami data were used in conjunction with numerical modelling to examine current evidence for the spatial extent of notable prehistoric events dating back as far as 3800 years BP. An outcome of this work was the recognition that any search for palaeotsunami evidence should be intrinsically linked with numerical modelling as a guide to identifying additional potential sites for further research in order to better understand the nature and extent of individual events. Another outcome of this study was the identification of several key island archipelagos that are worthy of focussed research because they have the potential to rapidly accelerate our understanding of the magnitude and frequency of past events. These include the centrally located Hawaiian Islands and the Marquesas archipelago that are exposed to Pacific-wide tsunamis from most circum-Pacific sources. It was also noted that there has been a dearth of research in some sectors of the Pacific Ocean, such as the western Pacific archipelagos of the Federated States of Micronesia, Palau, Guam, and Northern Mariana Islands, while conversely in other sectors a significant quantum of research is showing great promise such as in New Zealand, the Samoan archipelago, Cook Islands, and Vanuatu. The ultimate finding of this work is that while much has been achieved, much more remains to be done to better understand the magnitude and frequency of past events and the true nature of tsunami hazard and risk in the region.

Automated summary

There is a growing number of reported palaeotsunami sites in the Pacific region, but researchers have seldom sought evidence beyond the immediate site. In the past 150 years, the region has experienced significant earthquakes and tsunamis from various sources. Using existing palaeotsunami data and numerical modelling, researchers identified the need to link search for tsunami evidence with modelling to find additional sites and understand the nature and extent of prehistoric events. They also highlighted the importance of focused research on key island archipelagos to enhance understanding of past events.