Slip and Strain Accumulation Along the Sadie Creek Fault, Olympic Peninsula, Washington

Upper-plate faulting in the Olympic Peninsula of Washington State results from relative motion crustal blocks within Cascadia forearc and earthquake cycle processes along subduction zone. We reconstruct fault slip rates since ∼14 ka on Sadie Creek (SCF), north Mountains, using airborne lidar field mapping surficial deposits landforms optically stimulated luminescence radiocarbon dating. The SCF is a ≥14 km-long northwest-striking, subvertical, dextral strike-slip with subordinate dip-slip component. Laterally, offset debris flow channels cut into Late-Pleistocene younger surfaces show 4.0–24.5 m dip 0.7–6.5 m. Re-evaluation adjacent Lake Boundary (LCBCF) shows similar (4.5–29.7 m) (0.8–4.6 m). A deglacial age 14 paired largest—and presumably oldest—slip measurements produce minimum rate 1.3–2.3 mm/yr 0.05–0.5 mm/yr. Similarities geometry, kinematics, rate, timing between LCBCF suggest these faults represent one continuous geologic structure, North Geodetically constrained boundary element method models considering effects coseismic zone stresses upper plate structures comparable kinematics to those measured LCBCF, suggesting that acts as main strain-accommodating structure northern may be modulated by stress transferred earthquakes.