New kinematic models for Pacific‐North America motion from 3 Ma to present, I: Evidence for steady motion and biases in the NUVEL‐1A Model

Abstract

We use velocities derived from 2–4.5 years of continuous GPS observations at 21 sites on the Pacific and North American plates along with a subset of the NUVEL‐1A data to examine the steadiness of Pacific‐North America motion since 3.16 Ma, the transfer of Baja California to the Pacific plate, and the magnitude of biases in the NUVEL‐1A estimate of Pacific‐North America motion. We find that Pacific‐North America motion has remained steady since 3.16 Ma, but at rates significantly faster than predicted by NUVEL‐1A. In the vicinity of Baja California, our GPS‐derived model and recent seafloor spreading rates in the southern Gulf of California both indicate that the NUVEL‐1A model underestimates Pacific‐North America rates by 4±2 mm yr−1. Steady Pacific‐North America motion since 3.16 Myr and increasing seafloor spreading rates since 3.58 Myr in the Gulf of California imply that Pacific‐North America motion was partitioned between seafloor spreading in the Gulf of California and decelerating slip along faults in or offshore from the Baja peninsula.