The Most Parsimonious Ultralow‐Velocity Zone Distribution From Highly Anomalous SPdKS Waveforms
The Most Parsimonious Ultralow‐Velocity Zone Distribution From Highly Anomalous SPdKS Waveforms
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DOI：
10.1029/2020gc009467
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发表时间：
2020-12
期刊：
影响因子：
3.7
通讯作者：
M. Thorne;K. Leng;S. Pachhai;S. Rost;J. Wicks;T. Nissen‐Meyer
中科院分区：
文献类型：
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作者：
M. Thorne;K. Leng;S. Pachhai;S. Rost;J. Wicks;T. Nissen‐Meyer
超低速区（ULVZ）在核幔边界（CMB）的位置与各种特征有关，包括热点火山和大型低速区（LLVP）边界，但只有一小部分CMB区域被探测到ULVZ的存在。在这里，我们提出了一个新的下地幔异质性位置的地图，使用全球收集的高度异常的SPdKS记录的基础上的数据集超过58,000径向分量地震图，其中采样56.9%的CMB表面积。使用SPdKS地震相位推断非均质位置是具有挑战性的，因为震源与接收器侧的模糊性。由于这种模糊性，我们使用简约原则进行了反演。使用遗传算法进行反演，该算法重复数千次，以构建非均质概率图。该分析显示，在概率≥ 0.5、0.25和0.125时，高达1.3%、8.2%或19.7%的CMB可能含有ULVZ样异质性。这些不均匀性存在于所有下地幔环境中，包括高速和低速区域。此外，我们提出的证据表明，萨摩亚ULVZ可能是以前估计的两倍大，也提出了其他超大型ULVZ存在的证据，例如位于菲律宾东部的新发现的ULVZ。我们提供了新的证据ULVZ东部的菲律宾通过分析的ScP记录。
The locations of ultralow‐velocity zones (ULVZs) at the core‐mantle boundary (CMB) have been linked to a variety of features including hot spot volcanoes and large low‐velocity province (LLVP) boundaries, yet only a small portion of the CMB region has been probed for ULVZ existence. Here we present a new map of lower mantle heterogeneity locations using a global collection of highly anomalous SPdKS recordings based on a dataset of more than 58,000 radial component seismograms, which sample 56.9% of the CMB by surface area. The inference of heterogeneity location using the SPdKS seismic phase is challenging due to source‐versus receiver‐side ambiguity. Due to this ambiguity, we conducted an inversion using the principle of parsimony. The inversion is conducted using a genetic algorithm which is repeated several thousand times in order to construct heterogeneity probability maps. This analysis reveals that at probabilities ≥ 0.5, 0.25, and 0.125 up to 1.3%, 8.2%, or 19.7% of the CMB may contain ULVZ‐like heterogeneities. These heterogeneities exist in all lower mantle settings, including both high‐ and low‐velocity regions. Additionally, we present evidence that the Samoan ULVZ may be twice as large as previously estimated, and also present evidence for the existence of additional mega‐sized ULVZs, such as a newly discovered ULVZ located to the east of the Philippines. We provide new evidence for the ULVZ east of the Philippines through an analysis of ScP records.