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1. The Seismic Structure of the Antarctic Upper Mantle

   https://doi.org/10.1144/M56-2020-18  

   Wiens, Douglas A.; Shen, Weisen; Lloyd, Andrew (July 2021, Geological Society, London, Memoirs)

   null (Ed.)

   Abstract The deployment of seismic stations and the development of ambient noise tomography and new analysis methods provide an opportunity for higher resolution imaging of Antarctica. Here we review recent seismic structure models and describe their implications for the dynamics and history of the Antarctic upper mantle. Results show that most of East Antarctica is underlain by continental lithosphere to depths of ∼ 200 km. The thickest lithosphere is found in a band 500-1000 km west of the Transantarctic Mountains, representing the continuation of cratonic lithosphere with Australian affinity beneath the ice. Dronning Maud Land and the Lambert Graben show much thinner lithosphere, consistent with Phanerozoic lithospheric disruption. The Transantarctic Mountains mark a sharp boundary between cratonic lithosphere and the warmer upper mantle of West Antarctica. In the Southern Transantarctic Mountains, cratonic lithosphere has been replaced by warm asthenosphere, giving rise to Cenozoic volcanism and an elevated mountainous region. The Marie Byrd Land volcanic dome is underlain by slow seismic velocities extending through the transition zone, consistent with a mantle plume. Slow velocity anomalies beneath the coast from the Amundsen Sea Embayment to the Antarctic Peninsula likely result from upwelling of warm asthenosphere during subduction of the Antarctic-Phoenix spreading center. 

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2. Crustal and Uppermost Mantle Azimuthal Seismic Anisotropy of Antarctica From Ambient Noise Tomography

   https://doi.org/10.1029/2023JB027556  

   Zhou, Zhengyang; Wiens, Douglas A; Nyblade, Andrew A; Aster, Richard C; Wilson, Terry; Shen, Weisen (January 2024, Journal of Geophysical Research: Solid Earth)

   Abstract Seismic anisotropy provides essential information for characterizing the orientation of deformation and flow in the crust and mantle. The isotropic structure of the Antarctic crust and upper mantle has been determined by previous studies, but the azimuthal anisotropy structure has only been constrained by mantle core phase (SKS) splitting observations. This study determines the azimuthal anisotropic structure of the crust and mantle beneath the central and West Antarctica based on 8—55 s Rayleigh wave phase velocities from ambient noise cross‐correlation. An anisotropic Rayleigh wave phase velocity map was created using a ray—based tomography method. These data are inverted using a Bayesian Monte Carlo method to obtain an azimuthal anisotropy model with uncertainties. The azimuthal anisotropy structure in most of the study region can be fit by a two‐layer structure, with one layer at depths of 0–15 km in the shallow crust and the other layer in the uppermost mantle. The azimuthal anisotropic layer in the shallow crust of West Antarctica, where it coincides with strong positive radial anisotropy quantified by the previous study, shows a fast direction that is subparallel to the inferred extension direction of the West Antarctic Rift System. Fast directions of upper mantle azimuthal anisotropy generally align with teleseismic shear wave splitting fast directions, suggesting a thin lithosphere or similar lithosphere‐asthenosphere deformation. However, inconsistencies in this exist in Marie Byrd Land, indicating differing ancient deformation patterns in the shallow mantle lithosphere sampled by the surface waves and deformation in the deeper mantle and asthenosphere sampled more strongly by splitting measurements. 

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3. Mantle transition zone beneath West Antarctica: Expanded mapping in previously unstudied region

   Horton, A.C.; Emry, E.; Hansen, S.E.; van Wijk, J.; O'Donnell, J.P.; Brisbourne, A.; Stuart, G.W.; Anandakrishnan, S.; Aster, R.C.; Huerta, A.D.; et al (December 2018, American Geophysical Union)

   With the ongoing discussion of Earth structure under West Antarctica and how it relates to the extension and volcanism of the area, we explore the possibility of a hydrated or thermally perturbed mantle underneath the region. Using P-wave receiver functions, we focus on the Mantle Transition Zone (MTZ) and how its thickness fluctuates from the global average (240-260 km). Prior studies have explored the West Antarctic regions of Marie Byrd Land and the West Antarctic Rift, but we expand this to include ~3-5 years of recent, additional seismic data from the Amundsen Sea and Pine Island Bay regions. Several years of additional data from the Ronne-Fichtner Ice Shelf, Ellsworth Land, and Marie Byrd Land regions will help provide a more complete picture of the mantle transition zone. Data for this study was obtained from IRIS for earthquakes of a 5.5 magnitude or greater. We use an iterative, time domain deconvolution method, filtered with Gaussian widths of 0.5, 0.75, and 1.0. All events within their respective Gaussian filter have undergone quality check by removing waveforms that have lower than 85% fit and visually checking for clear outliers. We migrate the receiver functions to depth and stack, using both single station stacking and common conversion point (CCP) stacking. We migrate the CCP stacks assuming both 1D (AK-135) and 3D velocity models throughout the region. Preliminary results from single-station stacks beneath the Thurston Island and Amundsen Sea regions suggest that the MTZ thickness is similar to the global average and the depth to the transition zone appears to be depressed, with average transition zone boundaries appearing around 430 and 680 km. If the MTZ is thinner than the global average, it may be an indication for high temperature thermal anomalies or a plume under West Antarctica that may help explain the history of extension and uplift there. These results could be useful for glacial isostatic adjustment and/or geothermal heat flux models that attempt to understand ice sheet history and stability. 

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4. Seismic Evidence for Widespread Active Magmatism in Eastern Marie Byrd Land, Antarctica

   https://doi.org/10.1029/2025GL116647  

   Lucas, Erica M; Nyblade, Andrew A; Wiens, Douglas A; Aster, Richard C; Wilson, Terry J (October 2025, Geophysical Research Letters)

   Marie Byrd Land is a volcanically active province that overlaps with the Amundsen Sea Embayment, a region of the West Antarctic Ice Sheet that is experiencing particularly rapid ice mass loss. We locate 34 previously undetected seismic events (M_L1.2–3.2) and identify 251 additional similar events from 2019 to 2024 in eastern Marie Byrd Land. Located at crustal depths and of magmatic or tectonic origin, these events significantly expand the known geographic extent of such seismicity in West Antarctica. Seismicity is primarily located at Mount Takahe, ∼25 km south of the Crary Mountains, and ∼50 km west of the Kohler Range. Long‐period earthquakes at Mount Takahe have seismic characteristics consistent with active magmatic transport at crustal depths beneath the volcano. Glacio‐volcanic feedback due to ongoing ice mass loss may increase eruption frequency from active Marie Byrd Land volcanic systems, possibly perturbing future ice mass loss rates. 

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5. A joint inversion of receiver function and Rayleigh wave phase velocity dispersion data to estimate crustal structure in West Antarctica

   https://doi.org/10.1093/gji/ggaa398  

   Dunham, C K; O’Donnell, J P; Stuart, G W; Brisbourne, A M; Rost, S; Jordan, T A; Nyblade, A A; Wiens, D A; Aster, R C (September 2020, Geophysical Journal International)

   null (Ed.)

   SUMMARY We determine crustal shear wave velocity structure and crustal thickness at recently deployed seismic stations across West Antarctica, using a joint inversion of receiver functions and fundamental mode Rayleigh wave phase velocity dispersion. The stations are from both the UK Antarctic Network (UKANET) and Polar Earth Observing Network/Antarctic Network (POLENET/ANET). The former include, for the first time, four stations along the spine of the Antarctic Peninsula, three in the Ellsworth Land and five stations in the vicinity of the Pine Island Rift. Within the West Antarctic Rift System (WARS) we model a crustal thickness range of 18–28 km, and show that the thinnest crust (∼18 km) is in the vicinity of the Byrd Subglacial Basin and Bentley Subglacial Trench. In these regions we also find the highest ratio of fast (Vs = 4.0–4.3 km s–1, likely mafic) lower crust to felsic/intermediate upper crust. The thickest mafic lower crust we model is in Ellsworth Land, a critical area for constraining the eastern limits of the WARS. Although we find thinner crust in this region (∼30 km) than in the neighbouring Antarctic Peninsula and Haag-Ellsworth Whitmore block (HEW), the Ellsworth Land crust has not undergone as much extension as the central WARS. This suggests that the WARS does not link with the Weddell Sea Rift System through Ellsworth Land, and instead has progressed during its formation towards the Bellingshausen and Amundsen Sea Embayments. We also find that the thin WARS crust extends towards the Pine Island Rift, suggesting that the boundary between the WARS and the Thurston Island block lies in this region, ∼200 km north of its previously accepted position. The thickest crust (38–40 km) we model in this study is in the Ellsworth Mountain section of the HEW block. We find thinner crust (30–33 km) in the Whitmore Mountains and Haag Nunatak sectors of the HEW, consistent with the composite nature of the block. In the Antarctic Peninsula we find a crustal thickness range of 30–38 km and a likely dominantly felsic/intermediate crustal composition. By forward modelling high frequency receiver functions we also assess if any thick, low velocity subglacial sediment accumulations are present, and find a 0.1–0.8-km-thick layer at 10 stations within the WARS, Thurston Island and Ellsworth Land. We suggest that these units of subglacial sediment could provide a source region for the soft basal till layers found beneath numerous outlet glaciers, and may act to accelerate ice flow. 

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