USAP-DC

The geological structure and history of Antarctica remains poorly understood because much of the continental crust is covered by ice. Here, the PIs will analyze over 15 years of seismic data recorded by numerous projects in Antarctica to develop seismic structural models of the continent. The seismic velocity models will reveal features including crustal thinning due to rifting in West Antarctica, the structures associated with mountain building, and the boundaries between different tectonic blocks. The models will be compared to continents that are better understood geologically to constrain the tectonic evolution of Antarctica. In addition, the work will provide better insight into how the solid earth interacts with and influences the development of the ice sheet. Surface heat flow will be mapped and used to identify regions in Antarctica with potential melting at the base of the ice sheet. This melt can lead to reduced friction and lower resistance to ice sheet movement. The models will help to determine whether the earth response to ice mass changes occurs over decades, hundreds, or thousands of years. Estimates of mantle viscosity calculated from the seismic data will be used to better understand the pattern and timescales of the response of the solid earth to changes in ice mass in various parts of Antarctica.

The study will advance our knowledge of the structure of Antarctica by constructing two new seismic models and a thermal model using different but complementary methodologies. Because of the limitations of different seismic analysis methods, efforts will be divided between a model seeking the highest possible resolution within the upper 200 km depth in the well instrumented region (Bayesian Monte-Carlo joint inversion), and another model determining the structure of the entire continent and surrounding oceans extending through the mantle transition zone (adjoint full waveform inversion). The Monte-Carlo inversion will jointly invert Rayleigh wave group and phase velocities from earthquakes and ambient noise correlation along with P-wave receiver functions and Rayleigh H/V ratios. The inversion will be done in a Bayesian framework that provides uncertainty estimates for the structural model. Azimuthal anisotropy will be determined from Rayleigh wave velocities, providing constraints on mantle fabric and flow patterns. The seismic data will also be inverted for temperature structure, providing estimates of lithospheric thickness and surface heat flow. The larger-scale model will cover the entire continent as well as the surrounding oceans, and will be constructed using an adjoint inversion of phase differences between three component seismograms and synthetic seismograms calculated in a 3D earth model using the spectral element method. This model will fit the entire waveforms, including body waves and both fundamental and higher mode surface waves. Higher resolution results will be obtained by using double-difference methods and by incorporating Green's functions from ambient noise cross-correlation, and solving for both radial and azimuthal anisotropy.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Person	Role
Wiens, Douglas	Investigator and contact
Shen, Weisen	Co-Investigator

Antarctic Earth Sciences

Award # 1744883

USAP-1744883_1

None in the Database

Repository	Title (link)	Format(s)	Status
IRIS	CWANT-PSP: A 3-D shear velocity model from a joint inversion of receiver functions and surface wave dispersion derived from ambient noise and teleseismic earthquakes.	Not Provided	exists
IRIS	ANT-20: A 3D seismic model of the upper mantle and transition zone structure beneath Antarctica and the surrounding southern oceans	Not Provided	exists

1. Lloyd, A., Wiens, D., Zhu, H., Tromp, J., Nyblade, A., Aster, R.C., Hansen, S.E., Dalziel, I., Wilson, T., Ivins, E., Radially Anisotropic Seismic Structure of the Antarctic Upper Mantle Based on Full-Waveform Adjoint Tomography, J. Geophysics. Res., 10.1029/2019JB017823, 2019. (doi:10.1029/2019JB017823)
2. Shen, W., Wiens, D. A., Anandakrishnan, S., Aster, R. C., Gerstoft, P., Bromirski, P. D., et al. (2018). The crust and upper mantle structure of central and West Antarctica from Bayesian inversion of Rayleigh wave and receiver functions. Journal of Geophysical Research: Solid Earth, 123, 7824–7849 (doi:10.1029/2017JB015346)
3. Whitehouse, P. L., N. Gomez, M. A. King, D. A. Wiens (2019), Solid Earth change and the evolution of the Antarctic Ice Sheet, Nature Communications, 14 pp. (doi:10.1038/s41467-018-08068-y)
4. Shen, W., Wiens, D., Lloyd, A., & Nyblade, A. (2020). A geothermal heat flux map of Antarctica empirically constrained by seismic structure. Geophysical Research Letters, 47, e2020GL086955. (doi:10.1029/2020GL086955)
5. Wiens, D. A., Shen, W., & Lloyd, A. (2021). The Seismic Structure of the Antarctic Upper Mantle. Geological Society, London, Memoirs, M56–2020–18. (doi:10.1144/m56-2020-18)
6. Shen, W., Wiens, D. A., Lloyd, A. J., & Nyblade, A. A. (2020). A Geothermal Heat Flux Map of Antarctica Empirically Constrained by Seismic Structure. Geophysical Research Letters, 47(14). (doi:10.1029/2020gl086955)
7. Shen, W., Wiens, D. A., Anandakrishnan, S., Aster, R. C., Gerstoft, P., Bromirski, P. D., … Winberry, J. P. (2018). The Crust and Upper Mantle Structure of Central and West Antarctica From Bayesian Inversion of Rayleigh Wave and Receiver Functions. Journal of Geophysical Research: Solid Earth, 123(9), 7824–7849. (doi:10.1029/2017jb015346)
8. Lloyd, A. J., Wiens, D. A., Zhu, H., Tromp, J., Nyblade, A. A., Aster, R. C., … O’Donnell, J. P. (2020). Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography. Journal of Geophysical Research: Solid Earth, 125(3). (doi:10.1029/2019jb017823)
9. Xu, H., Luo, Y., Yang, Y., Shen, W., Yin, X., Chen, G., … Sun, S. (2020). Three‐Dimensional Crustal Structures of the Shanxi Rift Constructed by Rayleigh Wave Dispersion Curves and Ellipticity: Implication for Sedimentation, Intraplate Volcanism, and Seismicity. Journal of Geophysical Research: Solid Earth, 125(11). (doi:10.1029/2020jb020146)