The Pacific Ocean, encircled by subduction zones, is famously known as the “Ring of Fire,” characterized by frequent natural hazards such as earthquakes, volcanic eruptions, and tsunamis. The South Pacific, located in the ocean’s center, holds a treasure trove of geological history, yet details about its past natural hazards remain elusive. To unveil the mysteries of low-frequency but significant events, extensive geological research spanning thousands of years is essential.
To gather physical evidence of these past natural catastrophes, scientists can excavate volcanic ash and tsunami-transported marine sediments buried within the sedimentary layers of the region. Since March 2024, Japanese scientists have been actively engaged in a collaborative research project, JICA/SATREPS, in conjunction with Fiji’s Mineral Resources Department (MRD). This initiative, titled “Disaster Risk Reduction of Widespread Volcanic Hazards in Southwest Pacific Countries,” aims to enhance the understanding of past and present volcanic activities in the region to better mitigate future disasters, with particular attention on tsunamis generated by submarine volcanic activity.
As part of their efforts to investigate the tsunami history of Fiji, researchers conducted geological surveys on Viti Levu, Kadavu, and Vanua Balavu Islands over recent years. Preliminary findings indicate that Fiji may be more susceptible to significant tsunamis caused by submarine landslides rather than those triggered by earthquakes or volcanic eruptions. A historical instance illustrating this is the 1953 Suva tsunami, believed to have been instigated by a submarine landslide after a minor earthquake, which impacted Suva City. A subsequent event in 1960 may have involved a tsunami exceeding 10 meters in height, striking the village of Nabukelevu on Kadavu Island and necessitating its relocation to higher ground. Possible tsunami deposits have been identified at the former village location.
While the exact mechanism for tsunami generation remains uncertain, local submarine landslides are considered likely culprits, particularly due to the fragile nature of the volcanic rock in the region. It is suggested that significant but localized tsunamis may have frequently occurred around Fiji, often unnoticed unless they impacted populated areas. This implies a pattern where similar submarine landslides and resultant tsunamis could have recurred across the Fijian islands.
However, predicting such submarine landslides poses significant challenges. Therefore, evaluating potential risk areas through geological and geomorphological information will be pivotal in advancing this research. The work ahead promises to enhance disaster preparedness in Fiji and the surrounding areas while contributing to global understanding of volcanic and tsunami risks in similar geological contexts.
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