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Despite being separated by more than 1,500 kilometers (2,430 miles) of open ocean in the North Pacific, Hawai’i and Alaska’s Aleutian Islands share significant tsunami risks, particularly from seismic activity at the Aleutian subduction zone.

Map showing aftershock zones of great Aleutian Islands earthquakes in the 20th century
Aftershock zones of great Aleutian earthquakes in the 20th century.

The recently published study, "A Great Tsunami Earthquake Component of the 1957 Aleutian Islands Earthquake", sheds new light on the 1957 magnitude 8.6 Aleutian Islands earthquake, revealing critical details that enhance our understanding of tsunami threats to the Hawaiian Islands.

The 1957 earthquake, which occurred along a 1,200-kilometer stretch of the boundary between the Pacific and North America plates, was one of the largest earthquakes of the last century, unleashing a destructive tsunami that brought waves between 6 to 12 meters high (20-40 feet) to the Aleutian Islands and Hawaiʻi. Previous studies of this event were limited by sparse seismic data from the event and predicted that most of the slip in 1957 occurred in the western Aleutian Islands, yet this did not fully account for the high tsunami runup observed in Hawaiʻi.

Data from previous USGS-led studies (Witter et al., 2015, 2019; La Selle et al., 2019) mapping evidence of the 1957 tsunami in the eastern Aleutian Islands and Hawaii have been used by modelers to suggest substantial amounts of slip in the eastern Aleutians. By combining field observations and tide gauge records with modern tsunami modeling techniques, researchers have been able to paint a clearer picture of the earthquake's impact.

The recent study, which involves modeling tsunami runup on both the eastern Aleutian and Hawaiian Islands along with tide gauge records from across the Pacific, indicates that there was a shallow slip of between 12 and 26 meters over a 600-kilometer section of the eastern Aleutians. This slip, in addition to the more modest and deeper slip detected in the west, suggests a much larger seismic event than previously understood. The eastern slip alone corresponds to a magnitude 8.3-8.6 earthquake, forming a significant component of the overall magnitude 8.6-8.8 event, similar in scale to the adjacent 1946 Aleutian earthquake and tsunami.

This reexamination of the 1957 rupture underscores the potential tsunami hazards posed by the eastern Aleutian subduction zone to Hawaiʻi. It also highlights the need to investigate large prehistoric earthquakes through similar methods, using tsunami runup data derived from geological records to better understand their rupture processes.

Animated GIF of Aleutian Islands 1957 tsunami simulation
Animated GIF of Aleutian Islands 1957 tsunami simulation.

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