Late Holocene Relative Sea-Level Changes and the Earthquake Deformation Cycle Around Upper Cook Inlet, Alaska

Author(s): Ian Shennan; Sarah Hamilton

Year: 2005

Summary

This document details the history of relative seas level changes and earthquake deformation cycles in Cook Inlet, Alaska. Multiple peat-silt couplets preserved in tidal marsh sediment sequences suggest that numerous great plate boundary earthquakes caused the coast around Cook Inlet, Alaska, to subside over the past 3500 years. Field and laboratory analyses of the two youngest couplets record the well-documented earthquake of AD 1964 and the penultimate one, approximately 850 call yr BP. Diatom assemblages from a range of modern day estuarine environments from tidal flat through salt marsh to acidic bog produce quantitative diatom transfer function models for elevation reconstructions based on fossil samples. Only nine out of 124 fossil assemblages analyzed, including previously published data for the AD 1964 earthquake, have a poor modern analogue. Calibration of fossil samples indicate co-seismic subsidence of 1.5070.32m for AD 1964, similar to measurements taken after the earthquake, and 1.4570.34m for the 850 call yr BP earthquake. Elevation standard errors for individual fossil samples range from 0.08m in peat layers to 0.35m in silt units. Lack of a chronology within fossil silt units prevents identification of changes in the rate of recovery and land uplift between the post-seismic and inter-seismic periods.

Cite this Record

Late Holocene Relative Sea-Level Changes and the Earthquake Deformation Cycle Around Upper Cook Inlet, Alaska. Ian Shennan, Sarah Hamilton. 2005 ( tDAR id: 457968) ; doi:10.6067/XCV8457968

This Resource is Part of the Following Collections

Keywords

Investigation Types
Environment Research • Geophysical Survey • Historic Background Research

General
coastal environments • Cultural Resources • Earthquake • Earthquake Cycle • Earthquake Deformation Cycle • GPS • Joint Base Elmendorf-Richardson • Sea Level Research Unit

Geographic Keywords
Alaska (State / Territory) • Anchorage, AK • Kenai Peninsula • Upper Cook Inlet

Temporal Keywords
Late Holocene

Spatial Coverage

min long: -152.397; min lat: 59.169 ; max long: -146.691; max lat: 61.448 ;

Individual & Institutional Roles

Contact(s): Joint Base Elmendorf-Richardson CRM Manager

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