Possible Evidence of Tsunami at Kenmore (Sammamish River Outlet)

Quoted from: Shoreline Stratigraphy of Lake Washington: Implications for Holocene Crustal Strain and Earthquake Recurrence in the Cascadia Forearc
Text of Poster Session for Cascadia Penrose Conference, June 2000. Robert M. Thorson. Department of Geology and Geophysics, University of Connecticut, Storrs CT, 06269. thorson@geol.uconn.edu Phone 860-486-1396.

Tsunami at Kenmore (Sammamish River Outlet)

The high marsh of the Sammamish Delta at Kenmore contains a massive, locally graded sand "sheet "locally up to 40 cm thick that was present between 1.5 and 1.8 m depth in all four cores taken from this vicinity. This pebble-bearing, cleanly washed coarse gray sand is similar to that described by Atwater and Moore (1995) in Cultus Bay (Whidbey Island), and is thickest in the most landward core, becoming thinner and with multiple beds in deeper cores. Pending further work, this sand is interpreted as evidence for a single tsunami of Late Holocene age generated by uplifts of the Seattle Fault crossing Mercer Island.