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: 1345103
• 负责人: Barbara Romanowicz
• 金额: $ 5万
• 依托单位: University of California-Berkeley
• 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 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1345103&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.

由于温度、压力、成分和流量的变化，地球内部的弹性特性（例如密度、刚性、压缩性等）随着位置的不同而变化。在 20 世纪，地球科学家利用地震和爆炸发出的地震波来开发地球特性如何随深度变化的模型。这些努力产生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粒子物理和天文学等其他领域的参考中不可或缺。在过去的三十年中，全球地震学家更加复杂的努力已经产生了几代模型，这些模型不仅可以解释特性如何随深度变化，还可以横向变化。然而，尽管这些三维 (3D) 模型在大尺度上表现出引人注目的相似性，但它们所基于的方法、结构表示和数据集方面的差异阻碍了 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，并根据该数据集构建地幔的 3D 地震参考模型 (REM-3D)。作为一个具有完全量化的不确定性和权衡的社区参考模型，REM-3D 将促进地球成像研究、地震表征、内部深处温度和成分的推断，并提高中微子地球科学等新兴科学事业的实用性。研究人员将成立社区工作组，在参考模型和数据集开发过程中提供建议，并将组织研讨会来评估进展、评估模型和数据集性能、确定改进途径并推荐最大化模型采用的策略对地球深处社区的影响和效用。为此，研究人员征求了美国和国际各地地震学家、矿物物理学家、地球动力学家和地球化学家的意见。研究人员建议为地幔开发三维地震参考模型 (REM-3D)，根据剪切波速 (Vs)、压缩波速 (Vp)、密度 (ρ) 和 3 个附加参数进行参数化代表径向各向异性的参数。将开发该模型的两个版本，以明确拟合社区贡献的综合长周期地震数据集，一种根据球谐函数进行参数化，另一种作为与主要地理省份相对应的规范剖面。此外，他们还将编译、协调和分发长周期参考地震数据集，包括表面波色散测量、长周期绝对和微分体波测量以及自由振荡频率/衰减/和分裂。与之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数据（包括完整波形）的在线工具，以及主要设计用于使矿物物理学家和地球动力学家能够根据该参考模型或直接针对该参考模型验证测试模型的直接方法。参考数据集。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，并提出最大化地球深处社区模型采用和效用的策略。 REM-3D 将通过促进以下方面使更广泛的科学界受益： 1. 地震速度和密度的矿物学和热化学解释； 2. 识别地幔中的异常/非典型结构； 3、全球与区域层析模型对比； 4、地震波形解释，如特定震相的识别； 5. 3D地球结构反演需要起始模型或背景模型； 6. 使用长周期数据进行震源表征。 社区贡献的参考数据集的构建将使异常地震波传播时间、表面波色散、简正模分裂和波形特征的识别成为可能。此外，我们将创建的用于根据输入结构预测地震可观测值的工具将能够直接评估通过矿物物理和地球动力学实验和计算预测的潜在速度结构。