Were they all giants? Perspectives on late Holocene plate-boundary earthquakes at the northern end of the Cascadia subduction zone
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| Authors: | Hutchinson, I; Clague, J |
| Year: | 2017 |
| Journal: | Quat. Sci. Rev. 169: 29-49 Article Link (DOI) |
| Title: | Were they all giants? Perspectives on late Holocene plate-boundary earthquakes at the northern end of the Cascadia subduction zone |
| Abstract: | The relative magnitude of plate-boundary earthquakes at the northern end of the Cascadia subduction zone was assessed from the temporal concordance between the ages of coseismically buried late Holocene soils in southwest Washington, their counterparts in central and southern Cascadia, offshore turbidites, and paleoseismic deposits on the west coast of Vancouver Island. Only three of the seven buried soils in southwest Washington that can be reliably traced as buried soils or paleotsunami deposits in the coastal lowlands of south-central and southern Cascadia have well-dated counterparts in northern Cascadia. The three wide-ranging events date from Cascadia earthquakes Y (similar to 250 cal BP), U (similar to 1260 cal BP), and N (similar to 2520 cal BP). All three likely ruptured the entire plate margin, and therefore potentially qualify as "giants" (M-w >= 9). Deposits that may derive from tsunamis generated by earthquakes S (similar to 1570 cal BP), L (similar to 2870 cal BP) and J (similar to 3360 cal BP) can also be found in northern Cascadia, but the ages of these deposits are not yet well-enough constrained to determine whether they are coeval with their southern counterparts. Earthquake W (similar to 850 cal BP), appears to be present in the northern Cascadia paleoseismic record, but yields considerably older ages than in central Cascadia, and may be missing from southernmost Cascadia. The onshore record of an offshore turbidite (12) displays a similar spatiotemporal pattern to that of earthquake W. (C) 2017 Elsevier Ltd. All rights reserved. |
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