Full Waveform Ambient Noise Tomography for East Antarctica

Recent investigations in polar environments have examined solid-Earth-ice-sheet feedbacks and have emphasized that glacial isostatic adjustment, tectonic, and geothermal forcings exert first-order control on the physical conditions at and below the ice-bed interface and must be taken into account when evaluating ice-sheet evolution. However, the solid-Earth structure beneath much of Antarctica is still poorly constrained given the sparse distribution of seismic stations across the continent and the generally low seismicity rate. One region of particular interest is the Wilkes Subglacial Basin (WSB) in East Antarctica. During the mid-Pliocene warm period, the WSB may have contributed 3-4 m to the estimated 20 m rise in sea-level, indicating that this region could also play an important role in future warming scenarios. However, the WSB may have experienced notable bedrock uplift since the Pliocene; therefore, past geologic inferences of instability may not serve as a simple analogue for the future.

Using records of ambient seismic noise recorded by both temporary and long-term seismic networks, along with a full-waveform tomographic inversion technique, we have developed improved images of the lithospheric structure beneath East Antarctica, including the WSB. Empirical Green’s Functions with periods between 40 and 340 s have been extracted using a frequency-time normalization technique, and a finite-difference approach with a spherical grid has been employed to numerically model synthetic seismograms. Associated sensitivity kernels have also been constructed using a scattering integral method. Our results suggest the WSB is underlain by slow seismic velocities, with faster seismic structure beneath the adjacent Transantarctic Mountains and the Belgica Subglacial Highlands. This may indicate that the WSB is associated with a region of thinner lithosphere, possibly associated with prior continental rifting. The seismic heterogeneity highlighted in our model could have significant implications for understanding the geodynamic origin of WSB topography and its influence on ice-sheet behavior.

The model file and associated plotting scripts are provided.

极地环境领域的近期研究针对固体地球-冰盖反馈机制展开了考察，并强调冰川均衡调整（glacial isostatic adjustment）、构造作用与地热强迫对冰床界面及其下方的物理条件起到一级控制作用，因此在评估冰盖演化过程中必须将这些因素纳入考量。然而，由于南极大陆大部分区域的地震台站分布稀疏且整体地震活动率较低，南极多数区域下方的固体地球结构仍缺乏足够约束。其中备受关注的区域之一是东南极洲的威尔克斯冰下盆地（Wilkes Subglacial Basin, WSB）。在上新世中期暖期，威尔克斯冰下盆地可能曾导致海平面上升预估总量（20米）中的3~4米，这表明该区域在未来气候变暖情景中也可能发挥重要作用。不过，威尔克斯冰下盆地自上新世以来可能经历了显著的基岩隆升，因此过往基于地质观测得出的不稳定性推论，或许无法直接作为未来变化的类比参考。

本研究借助临时与长期地震台网记录的环境地震噪声数据，结合全波形层析成像反演（full-waveform tomographic inversion）技术，对东南极洲下方包括威尔克斯冰下盆地在内的岩石圈结构获得了更精准的成像结果。研究采用时频归一化技术提取了周期介于40~340秒的经验格林函数（Empirical Green’s Functions），并通过搭载球面网格的有限差分方法对合成地震图进行数值模拟。同时，我们还利用散射积分法构建了对应的灵敏度核函数（sensitivity kernels）。研究结果显示，威尔克斯冰下盆地下方呈现低速地震波速特征，而相邻的横贯南极山脉（Transantarctic Mountains）与贝尔吉卡冰下高地（Belgica Subglacial Highlands）下方则具有更高速的地震波结构。这一特征表明威尔克斯冰下盆地可能对应岩石圈较薄的区域，或许与早前的大陆裂谷作用存在关联。本模型所揭示的地震波非均质性，对于理解威尔克斯冰下盆地地形的地球动力学起源及其对冰盖行为的影响，具有重要的启示意义。

本数据集已附带模型文件及配套绘图脚本。