Seismic-stratigraphic interpretations (0.7 km deep; 1500 m/s two-way traveltime) reveal a bedrock erosional surface overlain by two distinct seismic facies. Overlying the bedrock is a 10 to 400 m-thick, heterogeneous, massive to hummocky, sub-parallel to discontinuous, and disrupted unit inferred to be Quaternary glacio-marine sediments. Shear zones within this unit are defined by near-vertical faults. Directly below the sediment-water interface, the youngest deposits are 10 to 50 m-thick, flat lying, acoustically continuos and inferred to be late Holocene ice-contact deltaic and glacial outwash deposits capped by more recent fine-grained marine sediments. The interpreted bedrock is defined by high-amplitude 20 to >40° east dipping reflectors, asymmetric "V"-shaped valleys, complex faulting patterns, and striking vertical relief. This seismic unit corresponds to 20-65° east dipping Eocene Upper Crescent Formation along Hood Canal’s western shoreline.
Major structural faulting is consistent with previously mapped fault races and is defined by abruptly terminating bedrock reflectors. Fault structures include high relief horst and graben, classic normal faults, crustal blocks with up to 200 m of apparent vertical displacement, pressure ridges, and probable remnant thrust fault structures. In southern Dabob Bay, a 2.0 km-wide north-northeast plunging graben structurally defines the southwestern shoreline of Toandos Peninsula. North of Quatsap Point, east-west trending bedrock topographic lows bounded by near-vertical faults may represent westward-projected fault splays of the Seattle Fault mapped 8 km to the east. Dextral strike-slip displacement may have formed a broad pull-apart basin south of Toandos Peninsula.