Coseismic Subsidence and Paleotsunami Run-Up Records from Latest Holocene Deposits in the Waatch Valley, Neah Bay, Northwest Washington, U.S.A.: Links to Great Earthquakes in the Northern Cascadia Margin
Peterson CD, Cruikshank KM, Darienzo ME, Wessen GC, Butler VL, Sterling SL. 2012. Coseismic Subsidence and Paleotsunami Run-Up Records from Latest Holocene Deposits in the Waatch Valley, Neah Bay, Northwest Washington, U.S.A.: Links to Great Earthquakes in the Northern Cascadia Margin. Journal of Coastal Research (JCR). :1-16
Representative shallow cores (1-2m depth) from the Waatch Valley (n=10) and from Neah Bay back-barrier wetlands (n=7) record four coseismic sibsidence events and associated paleotsunami inundations during the last 1300 years in the North Central Cascadia Margin. Three of the subsidence events (SUB1, SUB2b, and SUB3) correlate to reported great earthquakes dated at AD 1700, about 1.1 ka, and about 1.3 ka. An additional subsidence horizon (SUB2a), which is newly discovered in the study area, might correlate to a widely reported paleotsunami inundation, dated between 0.7 and 0.9 ka in the study region. The magnitudes of paleosubsidence in the Waatch Valley are modest (about 0.5-1.0 m), as are confirmed by the presence of ocean diatom taxa and beach sand grains. Long wave run-up in the low-gradient Waatch floodplain ranged from 2.5 to 4.5 km up-valley distance from the present tidal inlet shoreline. Paleotsunami overtopping of the Neah Bay barrier ridge (6-8 m elevation North American Vertical Dataum of 1988 [NAVD88] provides the first estimates of paleotsunami minimum run-up height at the entrance to the Juan de Fuca Strait.
- Type
- Journal Article
- Authors
- Peterson, Curt; Cruikshank, Kenneth; Darienzo, Mark; Wessen, Gary; Butler, Virginia; Sterling, Sarah
- Units
- OLYM
- Keywords
- Diatoms, Earthquakes, Radiocarbon Dating, subduction zone, Subsidence, Tsunami