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Conclusions

1. Canal-wide faulting patterns are seen throughout the dataset. Blind faults are observed propagating up section over vertical distances of up to 400 m and

define Quaternary sediment shear zones. These sediments infill an asymmetrical bedrock unit defined by "V"-shaped valleys and horst and graben topography. Shallow crustal deformation within the interpreted bedrock may represent high-angle strike-slip faulting driven by oblique subduction of the Pacific plate beneath North America.

2. Quaternary sediment fill between Seal Rock Park and Quatsap Point is shown to be < 10 m along the western shoreline of Dabob Bay and approach a maximum of 400 m along the longitudinal centerline of Hood Canal. This should be considered a minimum estimate and may vary by ± 25% in thickness.
3. Although this dataset may not allow such an interpretation to be made directly, evidence may exist within the interpreted profiles for active bedrock faulting with displacement rates close to those estimated for the Seattle and Southern Whidbey Island faults. Any proposed tectonic Puget Lowland earthquake models that incorporate Hood Canal should assume it to be an active structure capable of presenting a seismic hazard to residents in western Washington.
4. The fault trace of the Hood Canal-Discovery Bay fault zone defined by Gower et al. (1985) is consistent with up to 200 m of vertical bedrock offset, graben structures, and fault-bounded depressions observed in this dataset. Broad sediment shear zones are present along the westward-projected path of the Seattle Fault zone into Hood Canal. It is likely that the Hood Canal structure is structurally linked to the Seattle Fault zone as proposed by previous studies and experienced considerable coseismic deformation following the 1100 ca Seattle Fault earthquake.

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