Published In

Journal of Geological Research

Document Type

Article

Publication Date

2010

Subjects

Tsunami Pilot Study Working Group, Tsunamis -- Oregon -- Seaside

Abstract

The Seaside beach ridge plain was inundated by six paleotsunamis during the last ∼2500 years. Large runups (adjusted >10m in height) overtopped seawardmost cobble beach ridges (7m elevation) at ∼1.3 and ∼2.6 ka before present. Smaller paleotsunami (6−8m in height) likely entered the beach plain interior (4-5m elevation) through the paleo-Necanicum bay mouth. The AD 1700 Cascadia paleotsunami had a modest runup (6-7mheight), yet it locally inundated to 1.5 km landward distance. Bed shear stresses (100−3,300 dyne cm−2) are estimated for paleotsunami surges (0.5−2m depths) that flowed down slopes (0.002−0.017 gradient) on the landward side of the cobble beach ridges. Critical entrainment shear stresses of 1,130−1,260 dyne cm−2 were needed to dislodge the largest clasts (26−32 cm diameter) in paleotsunami coulees that were cut (100−200m width) into the landward side of the cobble ridges.

Description

Copyright 2010 Curt D. Peterson et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

http://www.hindawi.com/journals/jgr/2010/276989/

DOI

10.1155/2010/276989

Persistent Identifier

http://archives.pdx.edu/ds/psu/11362

Included in

Geology Commons

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