Juan de Fuca Ridge Spreading Rates

The Juan de Fuca Plate off the coast of Washington and Oregon, with the plate boundaries shown.

NUVEL absolute motions at four points along the ridge are shown, for both the JdF and Pacific plates.  Note that JdF velocities increase northward, and Pacific rates increase southward. JdF vectors are to the east of the ridge, and Pacific to the west.

The absolute velocities are not orthogonal to the ridge creast; both plates have a northward component of motion.

Velocities are correctly scaled and oriented.

Created in MICRODEM using Two plates motion option  on Plate rotation button on main MICRODEM toolbar.

The blue lines show the resultant different vector between the two plates, which gives their relative motions.  These were created in Paint, connecting the end points of the two vectors.

The memo box shows the magnitude of direction of this vector.

The motion along the ridge, by measuring the resultants and scaling them according to the scaled original velocities.

Note that spreading rate increases to the north, so that the Euler pole for JdF-PAC motion must lie to the south.

The spreading vectors are parallel to the transforms and perpendicular to the ridge segments, which was not obvious from the original absolute motions.

The rates here are the full spreading rates.

MICRODEM can automatically plot the resultant vectors, and place then centered on the location where they are computed, with the Resultant vector checkbox on the rotation control form.  These will be the full spreading rate.

Example for Juan de Fuca--North America trench.

Last revision 12/1/2016