Global reference seismological data sets: multimode surface wave dispersion
Global reference seismological data sets: multimode surface wave dispersion
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全球参考地震数据集：多模面波频散
DOI：
10.1093/gji/ggab418
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发表时间：
2021
影响因子：
2.8
通讯作者：
Durand, S
中科院分区：
文献类型：
--
作者：
Moulik, P;Lekic, V;Romanowicz, B;Schaeffer, A;Beucler, E;Debayle, E;Deuss, A;Durand, S
基模和泛音表面波传播的全球变化对地球上地幔、过渡带和中地幔的低频源特性和结构提供了独特的限制。我们通过协调来自全球八个研究小组的大型而多样化的Love波(4965万)和瑞雷波色散(177.66百万)目录，构建了一个多模色散测量的参考数据集。参考数据集汇总了全球分布的12个 地震台站记录的44个 871年地震的基模面波和多达6个泛音分支的色散测量结果。色散曲线是在S的25到250岁之间的一组参考周期上指定的，以确定相对于参考地球模型的传播相位异常。我们协调数据集的程序包括：(1)控制质量和挽救丢失的元数据；(2)确定不一致的测量结果和不一致的原因；(3)通过构建旅行时间观测的汇总射线来均衡地理覆盖；(4)结合数据类型来构建不同波长的相速度图，以评估数据集之间的一致性。我们检索了几种遗留汇编中丢失的台站和地震元数据，并编码了可伸缩格式，以便于在高性能计算系统上实现可重复性、易于存储和快速输入/输出。离群值可以归因于周期跳跃、台站极性问题或特定震中距离处的泛音干扰。通过评估相似路径上的数据集间一致性，我们经验性地量化了旅行时间测量中的不确定性。超过95%的基模色散测量结果在内部是一致的，但泛音的一致性恶化，特别是分支5和6。各种技术的原始相位异常之间的系统差异可归因于不同的理论近似、参考地球模型和处理方案。由总和数据集反演得到的相速度变化与质量控制贡献数据集的相速度变化高度相关(R≥为0.8)。基模色散的长波长变化(S的50-100%)在很大程度上与测量技术无关，高相关性扩展到∼25级。一致性随着分支数和周期的增加而降低；在较长的周期内，高度关联的结构只有在∼10的程度上才被发现(T>；对于S)，并且在∼8的程度上被发现。参考数据集只需要基模瑞利波相速度的2ζ方位变化；星表之间的2ζ方位变化图高度一致(R=0.60~0.80)。具有不确定性的参考数据有助于改进现有的测量技术，验证内部结构模型，计算局部或多尺度调查中的远震数据校正，并开发三维参考地球模型。
Global variations in the propagation of fundamental-mode and overtone surface waves provide unique constraints on the low-frequency source properties and structure of the Earth’s upper mantle, transition zone and mid mantle. We construct a reference data set of multimode dispersion measurements by reconciling large and diverse catalogues of Love-wave (49.65 million) and Rayleigh-wave dispersion (177.66 million) from eight groups worldwide. The reference data set summarizes measurements of dispersion of fundamental-mode surface waves and up to six overtone branches from 44 871 earthquakes recorded on 12 222 globally distributed seismographic stations. Dispersion curves are specified at a set of reference periods between 25 and 250 s to determine propagation-phase anomalies with respect to a reference Earth model. Our procedures for reconciling data sets include: (1) controlling quality and salvaging missing metadata; (2) identifying discrepant measurements and reasons for discrepancies; (3) equalizing geographic coverage by constructing summary rays for travel-time observations and (4) constructing phase velocity maps at various wavelengths with combination of data types to evaluate inter-dataset consistency. We retrieved missing station and earthquake metadata in several legacy compilations and codified scalable formats to facilitate reproducibility, easy storage and fast input/output on high-performance-computing systems. Outliers can be attributed to cycle skipping, station polarity issues or overtone interference at specific epicentral distances. By assessing inter-dataset consistency across similar paths, we empirically quantified uncertainties in traveltime measurements. More than 95 per cent measurements of fundamental-mode dispersion are internally consistent, but agreement deteriorates for overtones especially branches 5 and 6. Systematic discrepancies between raw phase anomalies from various techniques can be attributed to discrepant theoretical approximations, reference Earth models and processing schemes. Phase-velocity variations yielded by the inversion of thesummarydata set are highly correlated (R≥ 0.8) with those from the quality-controlled contributing data sets. Long-wavelength variations in fundamental-mode dispersion (50–100 s) are largely independent of the measurement technique with high correlations extending up to degree ∼25. Agreement degrades with increasing branch number and period; highly correlated structure is found only up to degree ∼10 at longer periods (T> 150 s) and up to degree ∼8 for overtones. Only 2ζazimuthal variations in phase velocity of fundamental-mode Rayleigh waves were required by the reference data set; maps of 2ζazimuthal variations are highly consistent between catalogues (R= 0.6–0.8). Reference data with uncertainties are useful for improving existing measurement techniques, validating models of interior structure, calculating teleseismic data corrections in local or multiscale investigations and developing a 3-D reference Earth model.
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