Crustal structure of the Washington continental margin from refraction data

Refraction data were collected in an onshore-offshore experiment in 1978 near Grays Harbor, Washington. Two-dimensional raytracing and synthetic seismo-grams were used to model the data along the refraction lines. The resulting velocity model uses a broad-scale subduction zone geometry to explain the major features of the data. The three main contributions of the onshore-offshore model are: (1) evidence for an approximately 9 ° dip of the subducting oceanic litho-sphere; (2) a clear indication of the point at which the subducting slab begins to bend beneath the margin; and (3) confirmation of the continuity of the slab from the buried trench offshore to beneath Puget Sound. The model also helps explain the distribution and stress orientation of earthquakes within the subduction zone