Field Observations and Modeling of the 1957 Earthquake and Tsunami on the Islands of the Four Mountains, Aleutian Islands, Alaska

Due to a lack of research in the Aleutian Islands, a comprehensive history of the Aleutian subduction zone is not developed; however, this study indicates that the Aleutian subduction zone is capable of generating magnitude ~9 earthquakes or larger in addition to trans-Pacific tsunamis. Comparison of simulated runup and observed runup will help to determine the characteristics of rupture in the eastern Aleutians. A recent survey of the tsunami wrackline produced by the 1957 Great Aleutian earthquake (M_w 8.6) indicates runup up to 17.5 m in the Islands of the Four Mountains (presented here). Combined with other nearfield observations of 22 m on Umnak and 18.5 m on Unalaska (USGS), our measurements establish the 1957 tsunami as a significant tsunami in the 20^th century. Through modeling this earthquake and tsunami and comparing simulations to nearfield observations, we conclude that the earthquake’s magnitude and amount of eastern slip are both higher than previously estimated. I propose several slip distributions that approximately recreate the observed runup; all of these distributions include high slip in the eastern portion of the aftershock zone, though the location of slip and intensity differ between models. No source model with a M_w = 8.6 was capable of generating the observed 1957 runup; the event was likely at least M_w> 8.9. Because nearfield observations are limited to those listed above, and seismic records are inadequate, a more precise solution to the rupture pattern cannot be determined.

Name thesis:degree_name

Master of Science (MS)

Discipline thesis:degree_discipline

Geological Sciences

Year dc:date.available

2015

Author dc:creator

• Griswold, Frances R.

Contributors dc:contributor

• Breanyn MacInnes
• David George
• Lisa Ely

• Tsunami
• 1957
• Aleutians
• Alaska
• Earth Sciences
• Geology
• Sedimentology

Language dc:language

English

Repository record dc:identifier

https://digitalcommons.cwu.edu/etd/201

OAI identifier oai:identifier

oai:digitalcommons.cwu.edu:etd-1194