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2019
White-Gaynor, AL, Nyblade AA, Aster RC, Wiens DA, Bromirski PD, Gerstoft P, Stephen RA, Hansen SE, Wilson T, Dalziel IW, Huerta AD, Winberry JP, Anandakrishnan S.  2019.  Heterogeneous upper mantle structure beneath the Ross Sea Embayment and Marie Byrd Land, West Antarctica, revealed by P-wave tomography. Earth and Planetary Science Letters. 513:40-50.   10.1016/j.epsl.2019.02.013   AbstractWebsite

We present an upper mantle P-wave velocity model for the Ross Sea Embayment (RSE) region of West Antarctica, constructed by inverting relative P-wave travel-times from 1881 teleseismic earthquakes recorded by two temporary broadband seismograph deployments on the Ross Ice Shelf, as well as by regional ice- and rock-sited seismic stations surrounding the RSE. Faster upper mantle P-wave velocities (similar to +1%) characterize the eastern part of the RSE, indicating that the lithosphere in this part of the RSE may not have been reheated by mid-to-late Cenozoic rifting that affected other parts of the Late Cretaceous West Antarctic Rift System. Slower upper mantle velocities (similar to -1%) characterize the western part of the RSE over a similar to 500 km-wide region, extending from the central RSE to the Transantarctic Mountains (TAM). Within this region, the model shows two areas of even slower velocities (similar to -1.5%) centered beneath Mt. Erebus and Mt. Melbourne along the TAM front. We attribute the broader region of slow velocities mainly to reheating of the lithospheric mantle by Paleogene rifting, while the slower velocities beneath the areas of recent volcanism may reflect a Neogene-present phase of rifting and/or plume activity associated with the formation of the Terror Rift. Beneath the Ford Ranges and King Edward VII Peninsula in western Marie Byrd Land, the P-wave model shows lateral variability in upper mantle velocities of +/- 0.5% over distances of a few hundred km. The heterogeneity in upper mantle velocities imaged beneath the RSE and western Marie Byrd Land, assuming no significant variation in mantle composition, indicates variations in upper mantle temperatures of at least 100 degrees C. These temperature variations could lead to differences in surface heat flow of similar to +/- 10 mW/m(2) and mantle viscosity of 10(2) Pa s regionally across the study area, possibly influencing the stability of the West Antarctic Ice Sheet by affecting basal ice conditions and glacial isostatic adjustment. (C) 2019 Elsevier B.V. All rights reserved.

2018
Shen, WS, Wiens DA, Anandakrishnan S, Aster RC, Gerstoft P, Bromirski PD, Hansen SE, Dalziel IWD, Heeszel DS, Huerta AD, Nyblade AA, Stephen R, Wilson TJ, Winberry JP.  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.   10.1029/2017jb015346   AbstractWebsite

We construct a new seismic model for central and West Antarctica by jointly inverting Rayleigh wave phase and group velocities along with P wave receiver functions. Ambient noise tomography exploiting data from more than 200 seismic stations deployed over the past 18years is used to construct Rayleigh wave phase and group velocity dispersion maps. Comparison between the ambient noise phase velocity maps with those constructed using teleseismic earthquakes confirms the accuracy of both results. These maps, together with P receiver function waveforms, are used to construct a new 3-D shear velocity (Vs) model for the crust and uppermost mantle using a Bayesian Monte Carlo algorithm. The new 3-D seismic model shows the dichotomy of the tectonically active West Antarctica (WANT) and the stable and ancient East Antarctica (EANT). In WANT, the model exhibits a slow uppermost mantle along the Transantarctic Mountains (TAMs) front, interpreted as the thermal effect from Cenozoic rifting. Beneath the southern TAMs, the slow uppermost mantle extends horizontally beneath the traditionally recognized EANT, hypothesized to be associated with lithospheric delamination. Thin crust and lithosphere observed along the Amundsen Sea coast and extending into the interior suggest involvement of these areas in Cenozoic rifting. EANT, with its relatively thick and cold crust and lithosphere marked by high Vs, displays a slower Vs anomaly beneath the Gamburtsev Subglacial Mountains in the uppermost mantle, which we hypothesize may be the signature of a compositionally anomalous body, perhaps remnant from a continental collision.