A kinematic model for the Gorda Deformation Zone as a diffuse southern boundary of the Juan de Fuca Plate

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Abstract
Several lines of evidence indicate that the space problem caused by southeastward motion of the Juan de Fuca plate toward the east‐west Mendocino transform is resolved by distributed deformation of the oceanic crust north of the transform. A kinematic model for this deformation based on the assumption of nondivergent flow (conservation of area) within the area known as the Gorda plate, and on the assumption of no subduction along the Mendocino transform, successfully matches the isochron pattern inferred from magnetic anomalies. The model assumes strain rate decreasing to zero approaching the rigid Juan de Fuca plate, with no sharp boundary or separate rigid area that would imply a discrete Gorda plate. This interpretation allows magnetic anomalies from south of the Blanco Fracture Zone to be used to constrain the kinematics of the Juan de Fuca plate. These anomalies imply a substantial change in the distance to the rotation pole at roughly 3 Ma, in addition to the clockwise shift in motion direction at 5 Ma.