Pole of rotation analysis of present-day Juan de Fuca Plate motion

Convergence rates between the Juan de Fuca and North America plates are calculated by means of their relative, present-day pole of rotation. Subduction rates, as measured normal to the strike of the Washington-Oregon trench, are predicted to range from about 40 mm/yr under Washington to 20 mm/yr under Oregon. An integral part of this analysis is the formulation of a numerical inversion scheme which calculates both the pole of rotation between two plates and the associated errors. This method is used to determine the Euler pole for Pacific-Juan de Fuca. This pole can then be vectorially added to previously published poles for North America-Pacific and “hot spot”-Pacific to obtain North America-Juan de Fuca and “hot spot”-Juan de Fuca, respectively. The errors associated with these resultant poles are also determined by propagating the errors of the two summed angular velocity vectors. With the assumption that hot-spots are fixed with respect to a mantle reference frame, if is computed that the average absolute velocity of the Juan de Fuca plate is approximately 15 mm/yr, thereby making it the slowest moving of the oceanic plates.

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