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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Global-scale analysis of the mantle Pds phases
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Global-scale analysis of the mantle Pds phases

机译：地幔Pds相的全球规模分析

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A global-scale analysis of travel times of the mantle Pds phases (converted from P to S from the discontinuity at a depth d beneath the receiver) is presented. Most of the data are related to P'410's and P'660's, recorded by the broadband stations of Geoscope, Incorporated Research Institutions for Seismology (IRIS) and other networks. In order to provide a good global-scale coverage, published measurements at 37 stations are complemented by our measurements at 45 stations. Lateral resolution of our data is many times higher than that of SS and its precursors, previously used for similar purposes, but we have fewer data in the oceans. Lateral variations of travel times of the major Pds phases are strongly correlated with the lateral P and S velocity variations in the uppermost mantle, as revealed by tomographic studies. The scaling coefficient between the teleseismic S and P residuals, as found from the variations of travel times of the major Pds phases, is around 3.7 for North America and around 3.3 for the rest of the world. Almost all the differential travel times t(P'660's) - t(P'410's) are in the range of +- 1 s, relative to the average value of 24.0 s. If the lateral variations of the velocities within the mantle transition zone (MTZ) can be neglected, the corresponding variations of thickness of the MTZ are in the range of +- 10 km, relative to the standard depth of 250 km, and do not show significant correlation with either velocities in the upper mantle above the MTZ or with the variations of thickness of the MTZ, as found in some recent studies of precursors to SS. There is a weak but marginally significant positive correlation between the variations of thickness of the MTZ inferred from our data and the S velocity variations in the MTZ, as given by Su et al. [1994]. This correlation suggests that both variables contain temperature-dependent components. Lateral variability of the MTZ is also manifested by extreme weakness of P'410's at several locations. This may indicate either anomalous topography on 410 km discontinuity or strong broadening of the otherwise sharp discontinuity. At some stations there are arrivals that can be interpreted as P'520's. This interpretation implies that the strengh and/or sharpness of 520 km discontinuity, as well as its depth, are laterally variable in a broad range.
机译：提出了地幔Pds相的传播时间的全球尺度分析（从接收器下方深度d处的不连续性从P转换为S）。大多数数据与P'410和P'660有关，这些数据由Geoscope，美国地震综合研究机构（IRIS）和其他网络的宽带站记录。为了提供良好的全球覆盖率，我们在45个站点的测量值对37个站点的已发布测量值进行了补充。我们数据的横向分辨率比以前用于类似目的的SS及其前体的横向分辨率高很多倍，但海洋中的数据却更少。层析成像研究表明，主要Pds相的行进时间的横向变化与最上地幔的横向P和S速度变化密切相关。从主要Pds相的传播时间变化可以发现，远震S和P残差之间的比例系数在北美约为3.7，在世界其他地区约为3.3。相对于平均值24.0 s，几乎所有差动行程时间t（P'660's）-t（P'410's）都在+1 s的范围内。如果可以忽略地幔过渡带（MTZ）内速度的横向变化，则相对于250 km的标准深度，MTZ厚度的相应变化在+-10 km范围内，并且不显示正如最近在SS前体研究中发现的那样，与MTZ上方上地幔的速度或MTZ厚度的变化具有显着的相关性。 Su等人给出的数据表明，根据我们的数据推断出的MTZ厚度变化与M速度中S速度变化之间存在微弱但微弱的正相关。 [1994]。这种相关性表明，这两个变量都包含温度相关的分量。 MTZ的横向可变性还表现为P'410在多个位置的极端弱点。这可能表明在410 km的不连续性上出现了异常的地形，或者表明了本来很陡峭的不连续性的强烈展宽。在某些车站，可以将其解释为P'520。这种解释意味着520 km的不连续性的强度和/或锐度以及其深度在较大范围内横向变化。

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