NUVEL-1A

NUVEL-1A is a global model describing the present-day relative velocities between the Earth's major tectonic plates. It is a refined update to the influential NUVEL-1 model, incorporating improved estimates of the geomagnetic reversal timescale to correct plate velocities. Developed by geophysicists Christopher DeMets, Donald Argus, and Richard Gordon, this model provided a critical quantitative framework for understanding global geodynamics and became a standard reference in the field for over a decade.

Overview and Development

The model was constructed to address a significant discrepancy identified in its predecessor, NUVEL-1. Research led by scientists like Steven Cande at the Lamont-Doherty Earth Observatory demonstrated that the geomagnetic polarity timescale (GPTS) used in the original model was inaccurate. This timescale, derived from studies of marine magnetic anomalies along mid-ocean ridges like the Mid-Atlantic Ridge and the East Pacific Rise, calibrates the timing of seafloor spreading. The team, utilizing data from institutions like the Scripps Institution of Oceanography and the University of California, San Diego, recalculated all plate velocities by adopting the revised CK95 geomagnetic timescale, resulting in systematically faster predicted speeds.

Model Parameters and Data Sources

NUVEL-1A defines the angular velocity vectors, or Euler poles, for the motion between twelve major tectonic plates, including the Pacific Plate, North American Plate, and Eurasian Plate. Its primary data sources were thousands of spreading rate measurements from marine magnetic anomalies and directions of plate motion from transform fault azimuths, largely compiled from surveys conducted by research vessels like those of the U.S. Geological Survey. The model also integrated information from earthquake slip vectors, particularly along subduction zones such as the Japan Trench and the Peru-Chile Trench, to constrain motions at convergent boundaries. This synthesis of magnetic, bathymetric, and seismic data from features like the San Andreas Fault and the Himalayas provided a robust global dataset.

Comparison with Previous Models

The key advancement over NUVEL-1 was a uniform increase in predicted plate velocities by approximately 4.5%. For example, the relative motion between the Pacific Plate and the Antarctic Plate along the Pacific-Antarctic Ridge was recalculated to be faster. This correction aligned the geological model more closely with space-geodetic measurements beginning to emerge from techniques like Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging. While models like RM2 had provided earlier estimates, NUVEL-1A offered superior global consistency and quickly superseded its predecessor as the default model for comparing GPS observations and testing tectonic hypotheses across regions from California to Southeast Asia.

Impact on Plate Tectonics

NUVEL-1A served as the definitive standard for quantifying global plate motions throughout the 1990s and early 2000s, influencing a vast range of research. It provided the foundational velocities for studies of continental deformation in areas like the Andes and the Alps, as well as for models of mantle convection and geodetic reference frames. The model was essential for interpreting early results from the International GNSS Service and for hazard assessments along plate boundaries like the Sumatran Trench. Its widespread adoption is evident in its use by organizations such as the International Association of Geodesy and in countless textbooks, solidifying concepts central to modern geology.

Limitations and Successors

Despite its utility, NUVEL-1A assumed all plates were rigid, an approximation that breaks down in diffuse boundary zones like the Basin and Range Province or the Aegean Sea. The advent of high-precision, continuous GPS networks, such as those operated by NASA and UNAVCO, revealed small but significant discrepancies between the geological model and direct geodetic measurements. These limitations prompted the development of newer models, including REVEL and GEODVEL, which directly incorporated space-geodetic data from the International Terrestrial Reference Frame. The current state-of-the-art is represented by models like ITRF2014-based global solutions, which provide real-time kinematic constraints, though NUVEL-1A remains a pivotal milestone in the history of geophysics.

Category:Plate tectonics Category:Geophysical models Category:1994 in science