Possible tsunami along the northwestern coast of the United States inferred from Indian traditions

Abstract

Subduction of the Juan de Fuca and Gorda plates beneath western North America presents a paradox; despite the fact that there is good evidence of 3 to 4 cm/yr of ongoing convergence, there is a remarkable paucity of either historic or instrumentally recorded shallow subduction earthquakes. Steady aseismic slip along the entire Cascadia subduction zone provides one explanation for this seismic quiescence. However, the Cascadia subduction zone shares many features, including temporal quiescence, with other subduction zones that have experienced very large shallow subduction earthquakes (Heaton and Kanamori, 1984). Yet, there is no direct geologic or historical evidence presently available to confirm that great shallow subduction earthquakes have occurred along the coast of Washington, Oregon, and northern California. However, there are reports describing Indian legends of great sea-level disturbances that may be related to large nearby earthquakes. In this letter, we briefly review the history of exploration and settlement of this region by nonnative people and then discuss legends from Indians in northern Washington and northern California.

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