Collaborative Research: Developing a Three-Dimensional Seismic Reference Earth Model (REM-3D) in Collaboration with the Community

合作研究：与社区合作开发三维地震参考地球模型 (REM-3D)

• 批准号: 1345101
• 负责人: John Shaw
• 金额: $ 5万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1345101&HistoricalAwards=false
• 关键词: Collaborative; Research; Developing; Three; Dimensional

Elastic properties of the Earth's interior (e.g. density, rigidity, compressibility, etc.) vary with location due to changes in temperature, pressure, composition, and flow. In the 20th century, Earth scientists have used seismic waves emitted by earthquakes and explosions to develop models of how Earth properties vary with depth. Community reference models that grew out of these efforts have proven indispensable in earthquake location, imaging of interior structure, understanding material properties under extreme conditions, and as a reference in other fields, such as particle physics and astronomy. Over the past three decades, more sophisticated efforts by seismologists across the globe have yielded several generations of models of how properties vary not only with depth, but also laterally. Yet, though these three-dimensional (3D) models exhibit compelling similarities at large scales, differences in the methodology, representation of structure, and dataset upon which they are based, have prevented the creation of 3D community reference models. The investigators propose to overcome these challenges by compiling, reconciling, and distributing a long period reference seismic dataset, from which they will construct a 3D seismic reference model (REM-3D) for the Earth's mantle. As a community reference model and with fully quantified uncertainties and tradeoffs, REM-3D will facilitate Earth imaging studies, earthquake characterization, inferences on temperature and composition in the deep interior, and be of improved utility to emerging scientific endeavors, such as neutrino geoscience. The investigators will set up community working groups that will serve to advise during the process of reference model and dataset development, and will organize a workshop to assess progress, evaluate model and dataset performance, identify avenues for improvement, and recommend strategies for maximizing model adoption in and utility for the deep Earth community. To this end, the investigators have solicited input from seismologists, mineral physicists, geodynamics, and geochemists from around the United States and internationally. The investigators propose to develop a three-dimensional seismic reference model (REM-3D) for the Earth's mantle, parameterized in terms of shear wavespeed (Vs), compressional wavespeed (Vp), density (ρ), and the 3 additional parameters representing radial anisotropy. Two versions of the model will be developed to explicitly fit the comprehensive, community-contributed long period seismic dataset, one parameterized in terms of spherical harmonics, and the other as canonical profiles corresponding to major geographic provinces. Furthermore, they will compile, reconcile, and distribute a long period reference seismic dataset, including surface wave dispersion measurements, long period absolute and differential body wave measurements, and free oscillation frequencies / attenuation / and splitting. Unlike previous reference models of Earth structure, REM-3D will have fully quantified. The investigators will also create online tools for model distribution and for predicting various seismic observables, including full waveforms, as well as tools designed primarily to enable mineral physicists and geodynamicists a straightforward way of (in)validating test models against this reference model or directly against the reference dataset. Finally, the investigators will set up community working groups and organize workshops that will advise on and evaluate model and dataset performance, identify avenues for improvement, and recommend strategies for maximizing model adoption in and utility for the deep Earth community. REM-3D will benefit the broader scientific community by facilitating: 1. Mineralogical and thermo-chemical interpretation of seismic velocities and density; 2. Identification of anomalous / atypical structures in the Earth's mantle; 3. Comparison of global and regional tomographic models; 4. Seismic waveform interpretation, such as the identification of particular seismic phases; 5. Inversion for 3D Earth structure requires a starting or background model; 6. Earthquake source characterization using long period data. The construction of a community-contributed reference dataset will make possible the identification of anomalous seismic wave travel times, surface wave dispersion, normal mode splitting, and waveform features. Furthermore, the tools for predicting seismic observables from input structures that we will create will enable direct evaluation of potential velocity structures predicted by mineral physics and geodynamics experiments and calculations.

地球内部的弹性特性（如密度、刚性、压缩性等）由于温度、压力、成分和流量的变化而随位置而变化。在20世纪世纪，地球科学家利用地震和爆炸发出的地震波建立了地球性质如何随深度变化的模型。从这些努力中成长起来的社区参考模型已被证明在地震定位，内部结构成像，了解极端条件下的材料特性以及作为其他领域（如粒子物理学和天文学）的参考中不可或缺。在过去的三十年里，地球仪的地震学家们进行了更复杂的努力，已经产生了几代模型，这些模型不仅可以解释属性如何随深度变化，而且还可以解释属性如何横向变化。然而，尽管这些三维（3D）模型在大尺度上表现出令人信服的相似性，但它们所基于的方法、结构表示和数据集的差异阻止了3D社区参考模型的创建。研究人员建议通过编译，协调和分发长期参考地震数据集来克服这些挑战，他们将从中构建地幔的3D地震参考模型（REM-3D）。作为一个社区参考模型，REM-3D具有充分量化的不确定性和权衡，将促进地球成像研究，地震定性，对深部温度和成分的推断，并提高对新兴科学努力的实用性，如中微子地球科学。研究人员将建立社区工作组，在参考模型和数据集开发过程中提供建议，并将组织一次研讨会，以评估进展情况，评估模型和数据集性能，确定改进途径，并建议最大限度地提高模型在地球深部社区的采用和效用的战略。为此，研究人员征求了来自美国和国际各地的地震学家、矿物物理学家、地球动力学家和地球化学家的意见。研究人员建议开发一个三维地震参考模型（REM-3D）的地幔，参数化的剪切波速（Vs），压缩波速（Vp），密度（#961;），和3个额外的参数代表径向各向异性。将开发两个版本的模型，以明确地适合全面的，社区贡献的长期地震数据集，一个参数化的球谐函数，和其他典型的配置文件对应的主要地理省份。此外，他们还将编制、协调和分发一个长周期参考地震数据集，包括面波频散测量、长周期绝对和差分体波测量以及自由振荡频率/衰减/和分裂。与以前的地球结构参考模型不同，REM-3D将完全量化。研究人员还将创建用于模型分布和预测各种地震观测值（包括全波形）的在线工具，以及主要旨在使矿物物理学家和地球动力学家能够直接根据参考模型或直接根据参考数据集验证测试模型的工具。最后，研究人员将成立社区工作组，并组织研讨会，就模型和数据集的性能提供建议和评估，确定改进途径，并建议最大限度地提高模型在地球深部社区的采用和效用的策略。REM-3D将有利于更广泛的科学界，促进：1。地震速度和密度的矿物学和热化学解释; 2.识别地球地幔中的异常/非典型结构; 3.全球和区域层析模型的比较; 4.地震波形解释，如识别特定的地震相位; 5.三维地球结构反演需要一个起始或背景模型; 6.用长周期资料描述震源特征。 社区贡献的参考数据集的建设将有可能识别异常地震波传播时间，表面波色散，正常模式分裂和波形特征。此外，我们将创建的从输入结构预测地震观测值的工具将能够直接评估矿物物理学和地球动力学实验和计算预测的潜在速度结构。