Do double ‘SS precursors’ mean double discontinuities?
Do double ‘SS precursors’ mean double discontinuities?
复制标题
双“SS 前体”是否意味着双不连续性？
DOI：
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
B. Romanowicz
中科院分区：
文献类型：
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作者：
Zhao;B. Romanowicz
摘要
在过去的二十年里，大量的SS前驱体被广泛地用于研究全球尺度上地幔不连续的存在和特征，以及在几个区域例子中。在这里，我们提供了对2010年美国移动台阵记录的Mb 6.7地震的SS前兆的观测。在这种特殊情况下，横向分量上的S660S前兆足够强，可以在整个阵列的各个地震记录上识别出来，而不需要任何叠加程序。观测到了两个S660S前兆，似乎表明在660公里深度附近的弹跳点区域存在双重不连续。然而，通过对一维和三维合成地震记录的仔细分析，我们发现，尽管它们的到达时间和慢度与SS前兆的理论值非常接近，但由于远离反弹点区的上地幔中地幔的不均质性，表面的“双前兆”是伪影。这表明，在从复杂的矿物学转变的角度解释双SS或PP前驱体之前，必须注意SS回弹点的适当方位覆盖。
SUMMARY
Stacks of SS precursors have been widely used in the past two decades to investigate the existence and characteristics of upper mantle discontinuities on a global scale as well as in several regional cases. Here, we present observations of SS precursors from an Mb 6.7 earthquake recorded at the US Transportable Array in 2010. In this particular case, the S660S precursors on the transverse component are strong enough to be identified on individual seismograms across the array without any stacking procedures. Two S660S precursors are observed, seeming to suggest double discontinuities around 660 km depth in the bounce point region. Through careful analysis of 1-D and 3-D synthetic seismograms, we however discover that, although they have arrival times and slownesses that are very close to the theoretical values of SS precursors, the apparent ‘double precursors’ are artefacts because of mantle heterogeneity in the upper mantle near the receivers away from the bounce point region. This suggests that caution must be taken about appropriate azimuthal coverage at the SS bounce point, before interpreting double SS or PP precursors in terms of complex mineralogical transitions.
SS前兆对东亚地区岩石圈和上地幔不连续面的研究
影响因子：
2.8
作者：
X. Yuan;M. Bianchi;R. Kind;J. Gossler
通讯作者：
J. Gossler