No‐net‐rotation model of current plate velocities incorporating plate motion model NUVEL‐1

Abstract

We present NNR‐NUVEL1, a model of plate velocities relative to the unique reference frame defined by requiring no‐net‐rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model NUVEL‐1 [DeMets et al., 1990]. Differences between NNR‐NUVEL1 and no‐net‐rotation plate motion model AM0‐2 [Minster and Jordan, 1978] are as large as 15 mm/yr. In NNR‐NUVEL1, the Pacific plate rotates in a right‐handed sense relative to the no‐net‐rotation reference frame at 0.67°/m.y. about 63°S, 107°E. This rotation nearly parallels, but is 32% slower than, the Pacific‐hotspot Euler vector of HS2‐NUVEL1, which is a global model of plate‐hotspot velocities constrained to consistency with NUVEL‐1 [Gripp and Gordon, 1990]. At Hawaii the Pacific plate moves relative to the no‐net‐rotation reference frame at 70 mm/yr, which is 25 mm/yr slower than the Pacific plate moves relative to the hotspots. Differences between NNR‐NUVEL1 and HS2‐NUVEL1 are described completely by a right‐handed rotation of 0.33°/m.y. about 49°S, 65°E. The 99% confidence ellipsoids for plate‐hotspot motion in model HS2‐NUVEL1 exclude the corresponding Euler vectors from model NNR‐NUVELl. Thus the no‐net‐rotation reference frame differs significantly from the hotspot reference frame. If the difference between reference frames is caused by motion of the hotspots relative to a mean mantle reference frame, then hotspots beneath the Pacific plate move with coherent motion towards the east‐southeast. Alternatively, the difference between reference frames may show that the uniform drag, no‐net‐torque reference frame, which is kinematically equivalent to the no‐net‐rotation reference frame, is based on a dynamically incorrect premise. Possible exceptions to the assumption of uniform drag include a net torque on the lithosphere due to attached subducting slabs and greater resistance to plate motion beneath continents than beneath oceans.