Abstract New P- and S-wave velocity models of the upper mantle from 100 to 400 km depth beneath the central portions of West Antarctica, obtained by inverting relative travel-times from teleseismic earthquakes recorded on Polar Earth Observing Network (POLENET/ANET) and UK Antarctic Network (UKANET) seismic stations between 2007 and 2017, reveal a heterogeneous upper mantle. A low velocity anomaly (−1.0% Vp; −2.0% Vs) imaged beneath Marie Byrd Land is attributed to thermally perturbed upper mantle of possible plume origin, and a low velocity anomaly imaged beneath the Pine Island Glacier and the mouth of Thwaites Glacier is interpreted as a rift-related thermal structure that may include warm mantle flowing from Marie Byrd Land. High velocity anomalies (≤0.8% Vp; 1.5% Vs) imaged in the central portion of the West Antarctic Rift System indicate the presence of lithosphere unmodified by tectonic activity since the Late Cretaceous formation of the rift system. Within the region of high velocities, localized low velocity anomalies beneath parts of the Bentley Subglacial Trench are suggestive of focused Cenozoic rifting. The models also show variable velocity structure beneath the Haag-Ellsworth Whitmore crustal block and low velocities beneath the Thurston Island-Eights Coast crustal block. The heterogenous upper mantle structure of central West Antarctica indicates that upper mantle temperatures could vary by 100 K or more over distances of less than 100 km, which may add complexity to solid earth-ice interactions and influence basal ice sheet conditions.

中文翻译：

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南极西部中部的纵波和横波速度结构：对西南极裂谷系统构造演化的影响

摘要 南极西部中部以下 100 至 400 公里深度上地幔的新 P 波和 S 波速度模型，通过对极地地球观测网络 (POLENET/ANET) 和2007 年至 2017 年间的英国南极网络 (UKANET) 地震台站揭示了一个异质的上地幔。在 Marie Byrd Land 下方成像的低速异常 (-1.0% Vp; -2.0% Vs) 归因于可能羽流起源的热扰动上地幔，而在 Pine Island Glacier 和 Thwaites Glacier 口下方成像的低速异常是解释为与裂谷相关的热结构，其中可能包括从玛丽伯德地流出的温暖地幔。高速异常（≤0.8% Vp；1. 5% Vs) 在西南极裂谷系统中部成像，表明自晚白垩世裂谷系统形成以来，存在未​​受构造活动影响的岩石圈。在高速区域内，本特利冰下海沟部分下方的局部低速异常表明新生代裂谷集中存在。这些模型还显示了 Haag-Ellsworth Whitmore 地块下方的可变速度结构和瑟斯顿岛-Eights Coast 地块下方的低速结构。中西部南极洲上地幔结构的异质性表明，在不到 100 公里的距离内，上地幔温度可能会变化 100 K 或更多，这可能会增加固体地冰相互作用的复杂性并影响基础冰盖条件。