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

南极洲和南大洋的综合地震和热模型：15 年地震勘探的综合

• 批准号: 1744883
• 负责人: Douglas Wiens
• 金额: $ 17.26万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1744883&HistoricalAwards=false
• 关键词: Comprehensive; Seismic; Thermal; Models; Antarctica

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.

南极洲的地质结构和历史仍然很少理解，因为大陆地壳都被冰覆盖。在这里，PIS将分析南极许多项目记录的15年的地震数据，以开发非洲大陆的地震结构模型。 地震速度模型将揭示特征，包括由于南极西部的裂缝，与山区建筑相关的结构以及不同构造块之间的边界。将模型与在地质上更好地理解以限制南极的构造进化的大陆进行比较。此外，这项工作将更好地了解固体土地与冰盖开发的相互作用和影响。表面热流将被映射并用于识别南极洲的区域，并在冰盖底部的潜在熔化。这种熔体会导致摩擦减少，并降低对冰盖运动的阻力。 这些模型将有助于确定地球对冰质量变化是否发生在数十年，数百或数千年的时间里。根据地震数据计算得出的地幔粘度的估计值将用于更好地了解南极各个部分中固体地球对冰量变化的响应的模式和时间表。该研究将通过使用不同的但互补的方法来构建两个新的地震模型和一个热模型来提高我们对南极结构的了解。由于不同的地震分析方法的局限性，努力将在寻求仪器良好区域上200 km深度内最高分辨率的模型（贝叶斯蒙特 - 卡洛关节倒置）中，以及确定整个大陆和周围海洋的结构的另一个模型，从地幔过渡区域扩展（Acacoint Full Pove Form Form Form Form Form Form Form Form Form Form Form Form Form Form Form Form iNversion）。 蒙特 - 卡洛反演将共同反转雷利波群和地震和环境噪声相关的相位速度以及P波接收器函数和雷利H/V比。反转将在贝叶斯框架中进行，该框架为结构模型提供不确定性估计。方位角各向异性将从瑞利波速度确定，从而对地幔织物和流动模式提供约束。地震数据还将倒置以进行温度结构，从而提供岩石圈厚度和表面热流动的估计。较大的模型将涵盖整个大陆以及周围的海洋，并将使用使用光谱元素方法在3D地球模型中计算出的三个组件地震图和合成地震图之间的相位差异来构建。该模型将适合整个波形，包括体波以及基本和更高模式的表面波。更高的分辨率结果将通过使用双差方法，并通过环境噪声互相关的绿色功能以及解决径向和方位角各向异性的求解。这一奖项反映了NSF的法定任务，并通过评估该基金会的智力优点和广泛的影响来审查Criteria。

项目成果

The Crust and Upper Mantle Structure of Central and West Antarctica From Bayesian Inversion of Rayleigh Wave and Receiver Functions

• DOI: 10.1029/2017jb015346
• 发表时间: 2018-09
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: W. Shen;D. Wiens;S. Anandakrishnan;R. Aster;P. Gerstoft;P. Bromirski;S. Hansen;I. Dalziel;D. Heeszel;A. Huerta;A. Nyblade;R. Stephen;Terry J. Wilson;J. P. Winberry

Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography

• DOI: 10.1029/2019jb017823
• 发表时间: 2020-03
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: A. Lloyd;D. Wiens;H. Zhu;J. Tromp;A. Nyblade;R. Aster;S. Hansen;I. Dalziel;T. J. Wilson;E. Ivins;J. O’Donnell

A Geothermal Heat Flux Map of Antarctica Empirically Constrained by Seismic Structure

• DOI: 10.1029/2020gl086955
• 发表时间: 2020-07
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: W. Shen;D. Wiens;A. Lloyd;A. Nyblade

Solid Earth change and the evolution of the Antarctic Ice Sheet

• DOI: 10.1038/s41467-018-08068-y
• 发表时间: 2019-01
• 期刊: Nature Communications
• 影响因子: 16.6
• 作者: P. Whitehouse;N. Gomez;M. King;D. Wiens