Collaborative Research: Anisotropy and Mantle Flow beneath Japan from Seismological Observatioans and Geodynamical Modeling

合作研究：地震观测和地球动力学模拟的日本地下各向异性和地幔流

• 批准号: 0337697
• 负责人: Robert van der Hilst
• 金额: --
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-15 至 2006-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337697&HistoricalAwards=false
• 关键词: Collaborative; Research; Anisotropy; Mantle; Flow

Proper characterization of elastic anisotropy can help understand the causes, mechanisms, and consequences of tectonic deformation in the upper mantle and in other regions of the Earth's deep interior and beneath regions of active tectonics. Unfortunately, our understanding of seismic anisotropy is still unsatisfactory and interpretation of seismological diagnostics of anisotropy (such as shear wave birefringence) is often ambiguous. Gaining full understanding of seismic anisotropy and flow beneath complex tectonic regions has, therefore, remained an outstanding challenge of modern seismology and geodynamics. In collaboration with colleagues in France, scientists from MIT and Colorado School of Mines propose to meet this challenge through the explicit integration of powerful data sets and forward and inverse modeling tools. In particular, they aim to improve the understanding of 3-D seismic anisotropy and tectonic deformation in the upper mantle near subduction zones, which are tectonic regions that are of particular societal interest because of their association with significant volcanic and seismic hazard. They will focus on Japan, where geophysical instrumentation is dense because of the need for the continuous monitoring of seismic and volcanic activity.Data from these dense networks can be obtained through the internet, thanks to scientists in Japan, and the MIT-CSM team has already assembled a large data set from 64 broadband seismic stations. Through examination of ~12,000 individual seismograms, they compiled a database of ~1330 high-quality shear wave splitting measurements for S, SKS/SKKS, and ScS, and more will be added later. They propose to improve the quantitative interpretation of the splitting maps by combining two complementary approaches. First, they wish to extend their numerical modeling of upper mantle flow from 2.5 to 3-D, incorporating (evolving) velocity boundary conditions and realistic geometries and rheologies. Second, they plan to develop a novel technique for tomographic inversion of the observed shear wave polarizations and split times. The flow models will be used to design the parameterization and regularization of the inversion, and, in turn, the seismic imaging results will be used to update the flow models. Such an explicitly cross-disciplinary approach will not only yield new insight into the 3-D anisotropy and flow field beneath Japan. Indeed, the powerful new tools and concepts for data analysis, modeling, and interpretation can also be applied to data from such new initiatives as USArray/Earthscope.

正确描述弹性各向异性可以帮助理解上地幔以及地球深层内部的其他区域和活动构造区域下方的构造变形的原因、机制和后果。 不幸的是，我们对地震各向异性的理解仍然不能令人满意，并且对各向异性（例如剪切波双折射）的地震学诊断的解释常常是含糊不清的。 因此，充分了解复杂构造区域下的地震各向异性和流动仍然是现代地震学和地球动力学的一个突出挑战。 麻省理工学院和科罗拉多矿业学院的科学家与法国同事合作，建议通过强大的数据集以及正向和逆向建模工具的显式集成来应对这一挑战。 特别是，他们的目标是提高对俯冲带附近上地幔的 3-D 地震各向异性和构造变形的理解，这些构造区域由于与重大火山和地震灾害相关而受到特别的社会关注。 他们将重点关注日本，由于需要持续监测地震和火山活动，那里的地球物理仪器非常密集。感谢日本的科学家，来自这些密集网络的数据可以通过互联网获得，并且 MIT-CSM 团队已经已经收集了来自 64 个宽带地震台的大型数据集。通过检查约 12,000 个单独的地震图，他们编制了约 1330 个 S、SKS/SKKS 和 ScS 高质量横波分裂测量结果的数据库，稍后还会添加更多内容。 他们建议通过结合两种互补的方法来改进分裂图的定量解释。 首先，他们希望将上地幔流的数值模型从 2.5 维扩展到 3 维，纳入（演化的）速度边界条件和现实的几何形状和流变学。其次，他们计划开发一种新技术，用于对观测到的剪切波偏振和分裂时间进行层析反演。 流动模型将用于设计反演的参数化和正则化，反过来，地震成像结果将用于更新流动模型。 这种明确的跨学科方法不仅会给日本地下的 3D 各向异性和流场带来新的见解。 事实上，用于数据分析、建模和解释的强大新工具和概念也可以应用于来自 USArray/Earthscope 等新举措的数据。