Improved Characterization of Ultralow‐Velocity Zones Through Advances in Bayesian Inversion of ScP Waveforms
Improved Characterization of Ultralow‐Velocity Zones Through Advances in Bayesian Inversion of ScP Waveforms
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通过 ScP 波形贝叶斯反演的进展改进超低速区的表征
DOI：
10.1029/2023jb026415
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Rost, Sebastian
中科院分区：
文献类型：
--
作者：
Pachhai, Surya;Thorne, Michael S.;Rost, Sebastian
超低速度带（ULVZs）已经使用各种地震相进行了研究；然而，它们的物理起源仍然知之甚少。由于短周期ScP波形对所有ULVZ弹性模量和厚度都很敏感，因此被广泛用于推断ULVZ特性。然而，由于路径衰减、相干噪声和源复杂性的影响，ScP波形变得更加复杂。为了解决这些问题，我们开发了一种分层贝叶斯反演方法，使我们能够同时反演多个事件的ScP波形，并考虑到路径衰减和相关噪声。用综合预测结果对反演方法进行了测试，结果表明，为了准确地恢复ULVZ参数，必须包含衰减，并且最可靠地恢复了ULVZ厚度和S波速度下降。同时利用多个事件可以减少相干噪声和源时间函数复杂性的影响，从而允许在分析中包含更多的数据。接下来，我们将该方法应用于在澳大利亚记录的291次ScP数据，这些数据来自珊瑚海下的核心-地幔边界。我们的研究结果表明，平均而言，约12公里厚的ULVZ使整个区域的S波速度降低了约14%，但采样区域南部的ULVZ性质比北部的变化更大。P波速度降低和密度扰动大多在10%以下。这些ScP数据显示在某些区域有多个ScP后光标，这可能表明复杂的三维ULVZ结构。
Ultralow‐velocity zones (ULVZs) have been studied using a variety of seismic phases; however, their physical origin is still poorly understood. Short period ScP waveforms are extensively used to infer ULVZ properties because they may be sensitive to all ULVZ elastic moduli and thickness. However, ScP waveforms are additionally complicated by the effects of path attenuation, coherent noise, and source complexity. To address these complications, we developed a hierarchical Bayesian inversion method that allows us to invert ScP waveforms from multiple events simultaneously and accounts for path attenuation and correlated noise. The inversion method is tested with synthetic predictions which show that the inclusion of attenuation is imperative to recover ULVZ parameters accurately and that the ULVZ thickness and S‐wave velocity decrease are most reliably recovered. Utilizing multiple events simultaneously reduces the effects of coherent noise and source time function complexity, which in turn allows for the inclusion of more data to be used in the analyses. We next applied the method to ScP data recorded in Australia for 291 events that sample the core‐mantle boundary beneath the Coral Sea. Our results indicate, on average, ∼12‐km thick ULVZ with ∼14% reduction in S‐wave velocity across the region, but there is a greater variability in ULVZ properties in the south than that in the north of the sampled region. P‐wave velocity reductions and density perturbations are mostly below 10%. These ScP data show more than one ScP post‐cursor in some areas which may indicate complex 3‐D ULVZ structures.
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影响因子：
--
作者：
A. Ross;H. Thybo;L. N. Solidilov
通讯作者：
L. N. Solidilov
影响因子：
5.3
作者：
H. Thybo;A.R Ross;A. Egorkin
通讯作者：
A. Egorkin
影响因子：
56.9
作者：
J. Revenaugh;R. Meyer
通讯作者：
J. Revenaugh;R. Meyer
DOI：
10.1029/2021jb021897
发表时间：
2021-06
期刊：
Journal of Geophysical Research: Solid Earth
影响因子：
--
作者：
J. Krier;M. Thorne;K. Leng;T. Nissen‐Meyer
通讯作者：
J. Krier;M. Thorne;K. Leng;T. Nissen‐Meyer
影响因子：
3.7
作者：
M. Thorne;K. Leng;S. Pachhai;S. Rost;J. Wicks;T. Nissen‐Meyer
通讯作者：
M. Thorne;K. Leng;S. Pachhai;S. Rost;J. Wicks;T. Nissen‐Meyer