Archaeological Evidence for Village Abandonment Associated with Late Holocene Earthquakes at the Northern Cascadia Subduction Zone

Abstract

Geologic evidence suggests that great (magnitude 8 or larger) earthquakes, or series of such earthquakes, occurred six times in the past 3000 yr at the northern Cascadia subduction zone. The archaeological record, and native oral traditions, demonstrate that native villages along the adjacent coasts of southern British Columbia and Washington State were occasionally abandoned in the late Holocene as a result of these earthquakes and associated tsunamis. We infer the temporal pattern of village occupation and abandonment from midden stratigraphy and from an activity index based on the probability distributions of radiocarbon ages at 30 archaeological sites in three regions of northern Cascadia. Deposits of probable tsunami origin are interbedded with, or bound, cultural strata at several sites. Earthquakes probably predate hiatuses in occupation, or periods of low inferred human activity, at many sites. The strongest correlation between earthquake incidence and site abandonment occurs in the Nootka Sound region. Effects of tsunamis vary with village location, coastal morphology, and late Holocene sea-level history.