Additionally, the largest earthquake to hit Seattle in the last 15 years was recorded by our OBS and OBH . All the wide-angle seismic data and two of the MCS lines have been processed, plotted, and analyzed on board for quality control and for initial scientific interpretations. The cruise ran smoothly and efficiently with the exception of a major storm and the loss of one OBS in the first week of operations.
Data quality is good to excellent.
Both wide-angle reflection and refraction data and the MCS data could detect the subducting oceanic crust under the continental margin to a distance of 20 km from shore. Three major differences between the continental margins of Washington and Oregon were discovered. The dip of the subducting plate may also decrease from south to north under the Washington margin. The second major difference is the average velocity of the sedimentary and crustal rocks overlying the subducting plate. These differences represent differences in crustal composition.