Current plate motions

Abstract

We determine best-fitting Euler vectors, closure-fitting Euler vectors, and a new global model (NUVEL-1) describing the geologically current motion between 12 assumed-rigid plates by inverting plate motion data we have compiled, critically analysed, and tested for self-consistency. We treat Arabia, India and Australia, and North America and South America as distinct plates, but combine Nubia and Somalia into a single African plate because motion between them could not be reliably resolved. The 1122 data from 22 plate boundaries inverted to obtain NUVEL-1 consist of 277 spreading rates, 121 transform fault azimuths, and 724 earthquake slip vectors. We determined all rates over a uniform time interval of 3.0m.y., corresponding to the centre of the anomaly 2A sequence, by comparing synthetic magnetic anomalies with observed profiles. The model fits the data well. Unlike prior global plate motion models, which systematically misfit some spreading rates in the Indian Ocean by 8-12mmyr-', the systematic misfits by NUVEL-1 nowhere exceed -3 mm yr-'. The model differs significantly from prior global plate motion models. For the 30 pairs of plates sharing a common boundary, 29 of 30 P071, and 25 of 30 RM2 Euler vectors lie outside the 99 per cent confidence limits of NUVEL-1. Differences are large in the Indian Ocean where NUVEL-1 plate motion data and plate geometry differ from those used in prior studies and in the Pacific Ocean where NUVEL-1 rates are systematically 5-20 mm yr-' slower than those of prior models. The strikes of transform faults mapped with GLORIA and Seabeam along the Mid-Atlantic Ridge greatly improve the accuracy of estimates of the direction of plate motion. These data give Euler vectors differing significantly from those of prior studies, show that motion about the Azores triple junction is consistent with plate circuit closure, and better resolve motion between North America and South America. Motion of the Caribbean plate relative to North or South America is about 7mmyr-' slower than in prior global models. Trench slip vectors tend to be systematically misfit wherever convergence is oblique, and best-fitting poles determined only from trench slip vectors differ significantly from their corresponding closure-fitting Euler vectors. The direction of slip in trench earthquakes tends to be between the direction of plate motion and the normal to the trench strike. Part of this bias may be due to the neglect of lateral heterogeneities of seismic velocities caused by cold subducting slabs, but the larger part is likely caused by independent motion of fore-arc crust and lithosphere relative to the overriding plate.

The recognition of transient compressional fault slow−slip along the northern shore of Hornsund Fjord, Sw Spitsbergen, Svalbard

“…Local directions of recent plate motion for this re− gion were derived from kinemetric models (e.g. DeMets et al 1990DeMets et al , 2010. They show that the Barent's shelf in this region is moving southeastwards at an azimuth of about 136°.…”

Plate kinematics in the western Pacific derived from geodetic observations

“…b No-net-rotation-Nuvel-1A (NNR-1A) model [DeMets et al, 1990;Argus and Gordon, 1991;DeMets et al, 1994]. c Angular velocity vectors were estimated in the ITRF94 reference frame.…”

Correlating measured and simulated dynamic responses of a tall building to long‐distance earthquakes

“…The Indo-Australia plate subducts below the Eurasia plate at a rate of about 67 mm per year [5]. The displacement between the two plates is partly accommodated by sudden movements.…”