Late Holocene paleoseismology of Shuyak Island, Alaska

• Published in: Quaternary science reviews 2018-12, Vol.201, p.380-395
• Main Authors: Shennan, Ian, Brader, Martin D., Barlow, Natasha L.M., Davies, Frank P., Longley, Chris, Tunstall, Neil
• Format: Article
• Language: English
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2018.10.028

We report stratigraphic evidence of land-level changes along the eastern portion of the Alaska-Aleutian megathrust. Four marshes on Shuyak Island record variable amounts of coseismic deformation during four pre-20th century earthquakes. We combine these data with paleoseismic evidence from across the Kodiak, Kenai and Prince William Sound segments of the megathrust. These indicate that in the last 2000 years, AD 1964 was the only one to rupture all three segments simultaneously and generate a Mw 9.2 earthquake. The Kodiak segment ruptured independently on four further occasions with magnitudes > Mw 8.0; in AD 1788 and c.400 (440–320) BP, and independently but around the times of great earthquakes in the Prince William Sound segment c.850 and c.1500 BP. [Display omitted] •New evidence of land-level changes, eastern part of the Alaska-Aleutian megathrust.•Marshes on Shuyak Island record deformation in four pre-20th century earthquakes.•AD 1964 was the only Mw 9.2 earthquake, rupturing three segments of the megathrust.•The Kodiak segment ruptured independently on four occasions with magnitudes > Mw 8.0•The different patterns of rupture can contribute to seismic hazard models.