Foundations for a multiscale collaborative global Earth model
Foundations for a multiscale collaborative global Earth model
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DOI：
10.1093/gji/ggv439
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发表时间：
2015-11
影响因子：
2.8
通讯作者：
M. Afanasiev;D. Peter;K. Sager;S. Simutė;L. Ermert;L. Krischer;A. Fichtner
中科院分区：
文献类型：
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作者：
M. Afanasiev;D. Peter;K. Sager;S. Simutė;L. Ermert;L. Krischer;A. Fichtner
我们提出了一个计算框架，用于将局部到全球的地震数据同化为描述所有地震可达尺度上的地球结构的一致模型。该协作地震地球模型(CSEM)旨在满足以下要求：(I)灵活的几何参数化，能够捕捉地形和水深，以及潜在可分辨结构的所有方面，包括小尺度不均匀和内部不连续的变形。(2)任何特定波动方程解算器的独立性，以便能够组合适用于不同类型地震数据的反演技术。(3)允许完全各向异性并允许衰减和密度变化的物理参数。虽然并非所有这些参数都是可解析的，但约束任何参数子集的数据同化应该是可能的。(4)在有新的数据或反演技术出现时，通过纳入任何规模的更新来适应连续改进的能力。(V)支持协作构建地球模型。初始CSEM的结构用变分辨率四面体网格表示。它由一个长波长的3-D全球模型组装而成，其中嵌入了几个区域尺度的断层成像。我们用来自日本和西地中海的两个例子说明了CSEM连续更新的工作流程，在这两个例子中，我们使用全波形反演来约束较小尺度的结构。此外，我们展示了CSEM作为一种工具的能力，将不同的断层扫描技术与欧洲联合全波形和旅行时间射线断层扫描相结合。这种组合扩大了单独技术的可开发频率范围，从而提高了分辨率。我们使用全球225次有记录的地震的长周期参考数据集，进行了两次全地球全波形反演。在CSEM开发的早期阶段，广泛的全球更新主要是从初始CSEM的组装中移除人工制品。在CSEM未来的演变过程中，参考数据集将被用来解释小规模细化对大尺度全球结构的影响。CSEM作为一个计算框架，旨在帮助弥合地方、区域和全球层析成像之间的差距，并为全球多尺度地球模型的发展作出贡献。虽然目前的建设是概念的第一次验证，但未来的完善和补充将需要社区的参与，这在现阶段已经是受欢迎的。
We present a computational framework for the assimilation of local to global seismic data into a consistent model describing Earth structure on all seismically accessible scales. This Collaborative Seismic Earth Model (CSEM) is designed to meet the following requirements: (i) Flexible geometric parametrization, capable of capturing topography and bathymetry, as well as all aspects of potentially resolvable structure, including small-scale heterogeneities and deformations of internal discontinuities. (ii) Independence of any particular wave equation solver, in order to enable the combination of inversion techniques suitable for different types of seismic data. (iii) Physical parametrization that allows for full anisotropy and for variations in attenuation and density. While not all of these parameters are always resolvable, the assimilation of data that constrain any parameter subset should be possible. (iv) Ability to accommodate successive refinements through the incorporation of updates on any scale as new data or inversion techniques become available. (v) Enable collaborative Earth model construction. The structure of the initial CSEM is represented on a variable-resolution tetrahedral mesh. It is assembled from a long-wavelength 3-D global model into which several regional-scale tomographies are embedded. We illustrate the CSEM workflow of successive updating with two examples from Japan and the Western Mediterranean, where we constrain smaller scale structure using full-waveform inversion. Furthermore, we demonstrate the ability of the CSEM to act as a vehicle for the combination of different tomographic techniques with a joint full-waveform and traveltime ray tomography of Europe. This combination broadens the exploitable frequency range of the individual techniques, thereby improving resolution. We perform two iterations of a whole-Earth full-waveform inversion using a long-period reference data set from 225 globally recorded earthquakes. At this early stage of the CSEM development, the broad global updates mostly act to remove artefacts from the assembly of the initial CSEM. During the future evolution of the CSEM, the reference data set will be used to account for the influence of small-scale refinements on large-scale global structure. The CSEM as a computational framework is intended to help bridging the gap between local, regional and global tomography, and to contribute to the development of a global multiscale Earth model. While the current construction serves as a first proof of concept, future refinements and additions will require community involvement, which is welcome at this stage already.