Abstract

A stratigraphic and microfossil record of coseismic land-level changes and tsunami deposits from Old Harbor, Central Kodiak Island, Alaska

Highlights

  • The Alaska-Aleutian subduction zone is one of the most seismically active subduction zones in the world (United States Geological Survey, 2014)

  • We aimed to answer three main research questions: 1) Is the lithological evidence of paleoearthquakes at Old Harbor comparable with other records from nearby sites to the north and south? 2) Is there evidence for the AD 1788 earthquake at Old Harbor? 3) Can diatoms and/or grain-size data aid in identifying whether or not clastic layers are deposited by tsunami? To address these questions, we performed a complete lithologic, grain-size, and diatom analysis on a sediment core collected from Big Creek marsh in Old Harbor on Kodiak Island (Figure 2)

  • We described the stratigraphy at Big Creek and Bear Terrace using 11 cores and 7 cores, respectively (23-100 cm long)

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Summary

Introduction

The Alaska-Aleutian subduction zone is one of the most seismically active subduction zones in the world (United States Geological Survey, 2014). Almost the entire subduction zone interface ruptured in the 20th century with seven earthquakes greater than M8.0 in 1987, 1965, 1964, 1957, 1946, 1938, and 1906. The largest of these was the M9.2 1964 earthquake, rupturing the eastern segments of the subduction zone (Carver and Plafker, 2008; Plafker 1969). In order to learn more about historic and prehistoric earthquakes before the installation of seismometers along the Alaska-Aleutian megathrust, we employ paleoseismology methods to investigate the record of earthquakes and tsunamis recorded in the sediments along the subduction zone. Our results will help better assess seismic hazards in the region and inform future scientific investigations in the area

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