Palaeoseismological records of multiple great earthquakes in south-central Alaska: a 4000 year record at Girdwood.

Shennan, I.; Barlow, N.L.M.; Combellick, R.

Abstract

Analysis of sediment sequences beneath a tidal marsh at Girdwood, Alaska, record seven great earthquakes in the past 4000 years, including the Mw = 9.2 earthquake of March 27, 1964. The key theme that arises from studies of crustal deformation for the south central Alaska earthquake zone over timescales of the last few millennia is one of temporal and spatial variability. We have quantitative data to show both temporal and spatial similarities and differences for different earthquake cycles. There is not a fixed recurrence interval. The shortest interval is between ~180 and 720 years. The longest interval is 790–920 years, which is between the penultimate and the 1964 earthquakes. Estimates of subsidence at Girdwood for each earthquake show values similar to or less than that recorded in 1964. Similarities between each earthquake cycle leads to a model for the Girdwood area with coseismic subsidence, followed by rapid postseismic uplift in the decades after the earthquake. This merges into centuries of slower interseismic uplift before a period of preseismic subsidence. Correlations with sites beyond Girdwood reveal regional-scale temporal variability and spatial heterogeneity in the crustal deformation processes.

Citation

Shennan, I., Barlow, N., & Combellick, R. (2008). Palaeoseismological records of multiple great earthquakes in south-central Alaska: a 4000 year record at Girdwood. In J. Freymueller, P. Haeussler, R. Wesson, & G. Ekstrom (Eds.), Active tectonics and seismic potential of Alaska (185-199). AGU Geophysical Monograph Series

• Publication Date: 2008
• Deposit Date: May 19, 2010
• Pages: 185-199
• Series Number: 179
• Book Title: Active tectonics and seismic potential of Alaska.
• Chapter Number: 10
• Public URL: https://durham-repository.worktribe.com/output/1660986