Comprehensive Seismic and Thermal Models for Antarctica and the Southern Oceans: A Synthesis of 15-years of Seismic Exploration

南极洲的地质结构和历史仍然知之甚少，因为大陆地壳的大部分被冰覆盖。在这里，PI将分析南极洲许多项目记录的超过15年的地震数据，以开发该大陆的地震结构模型。地震速度模型将揭示包括西南极裂谷导致的地壳减薄、与造山有关的构造以及不同构造块之间的边界等特征。这些模型将与地质学上更好理解的大陆进行比较，以限制南极洲的构造演化。此外，这项工作将更好地洞察固体地球如何与冰盖相互作用并影响冰盖的发展。将绘制表面热流图，并用来识别南极洲冰盖底部可能融化的地区。这种融化可以减少摩擦，降低冰盖移动的阻力。这些模型将有助于确定地球对冰块变化的响应是在几十年、数百年还是数千年内发生的。根据地震数据计算的地幔粘度估计将被用来更好地了解南极不同地区固体地球对冰块变化的响应模式和时间尺度。这项研究将通过使用不同但互补的方法构建两个新的地震模型和一个热模型来提高我们对南极洲结构的认识。由于不同地震分析方法的局限性，工作将分为两种：一种是寻求在井区上方200公里深度范围内获得尽可能高分辨率的模型(贝叶斯-蒙特卡罗联合反演)，另一种是确定整个大陆和通过地幔过渡带延伸的周围海洋的结构的模型(伴随全波形反演)。蒙特卡罗反演将联合反演地震和环境噪声相关的瑞雷波群和相速度，以及P波接收函数和瑞利H/V比。反演将在贝叶斯框架内进行，该框架为结构模型提供不确定性估计。方位各向异性将由瑞雷波速度确定，从而对地幔组构和流动模式提供约束。地震数据还将反演温度结构，提供岩石圈厚度和地表热流的估计。更大比例尺的模型将覆盖整个大陆以及周围海洋，并将使用三分量地震图和使用谱元素方法在3D地球模型中计算的合成地震图之间的相位差的伴随反演来构建模型。该模型将适用于所有的波形，包括体波以及基波和高模表面波。更高分辨率的结果将通过使用双差分方法和纳入来自环境噪声互相关的格林函数，以及求解径向和方位各向异性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.