Seismic Azimuthal Anisotropy Beneath Australia is Investigated using Splitting of the Teleseismic PKS, SKKS, and SKS Phases to Delineate Asthenospheric Flow and Lithospheric Deformation Beneath One of the Oldest and Fast-Moving Continents on Earth. in Total 511 Pairs of High-Quality Splitting Parameters Were Observed at 116 Seismic Stations. Unlike Other Stable Continental Areas in Africa, East Asia, and North America, Where Spatially Consistent Splitting Parameters Dominate, the Fast Orientations and Splitting Times Observed in Australia Show a Complex Pattern, with a Slightly Smaller Than Normal Average Splitting Time of 0.85 ± 0.33 S. on the North Australian Craton, the Fast Orientations Are Mostly N-S, which is Parallel to the Absolute Plate Motion (APM) Direction in the Hotspot Frame. Those Observed in the South Australian Craton Are Mostly NE-SW and E-W, Which Are Perpendicular to the Maximum Lithospheric Horizontal Shortening Direction. in East Australia, the Observed Azimuthal Anisotropy Can Be Attributed to Either APM Induced Simple Shear or Lithospheric Fabric Parallel to the Strike of the Orogenic Belts. the Observed Spatial Variations of the Seismic Azimuthal Anisotropy, When Combined with Results from Depth Estimation Utilizing the Spatial Coherency of the Splitting Parameters and Seismic Tomography Studies, suggest that the Azimuthal Anisotropy in Australia Can Mostly Be Related to Simple Shear in the Rheologically Transition Layer between the Lithosphere and Asthenosphere. Non-APM Parallel Anisotropy is Attributable to Modulations of the Mantle Flow System by Undulations of the Bottom of the Lithosphere, with a Spatially Variable Degree of Contribution from Lithospheric Fabric.
K. Ba et al., "Seismic Azimuthal Anisotropy Beneath a Fast Moving Ancient Continent: Constraints from Shear Wave Splitting Analysis in Australia," Journal of Geophysical Research: Solid Earth, vol. 128, no. 2, article no. e2022JB025866, American Geophysical Union; Wiley, Feb 2023.
The definitive version is available at https://doi.org/10.1029/2022JB025866
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
Australian continent; mantle flow; seismic anisotropy; shear wave splitting
International Standard Serial Number (ISSN)
Article - Journal
© 2023 American Geophysical Union; Wiley, All rights reserved.
01 Feb 2023