The 520 km discontinuity
The 520 km discontinuity
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520公里的不连续面
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
M. Bostock
中科院分区：
文献类型：
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作者：
P. Cummins;B. Kennett;J. R. Bowman;M. Bostock
尽管最早的一些关于上地幔520公里深度附近地震间断的建议来自对澳大利亚北部该构造的地震研究，但最近部署的便携式短周期仪器阵列的结果是模棱两可的。在这些实验中记录的数百次地震中，只有一小部分提供了可以帮助限制不连续性质的数据。在少数能够解决这种不连续是否存在的问题的地震记录中，大多数表明，在深度不到540公里的地方，它不作为一个尖锐的特征(即厚度不到50公里)存在。然而，这些数据并不限制深度大于540公里的不连续面的存在。此外，速度增加可以在很大的深度范围内分布；即使是50公里的过渡也不会出现在短周期观测中，并且在近垂直入射时仍然提供足够的反射率，以与在地幔中陡峭行进的波的长周期观测相兼容。
Although some of the earliest suggestions of a seismic discontinuity near 520 km depth in the upper mantle came from seismic studies of the structure to the north of Australia, results from more recent deployments of portable arrays of short-period instruments are equivocal. Of the several hundred earthquakes recorded during these experiments, only a small fraction provide data that could help to constrain the properties of the discontinuity. Of the few earthquake recordings that can address the question of whether such a discontinuity exists, most indicate that it does not exist as a sharp feature (i.e., less than 50 km thick) at depths of less than 540 km. The data do not, however, constrain the existence of a discontinuity at depths greater than 540 km. Furthermore, the velocity increase could be distributed over a significant depth range; even a 50-km transition would not appear in the short-period observations and still provide sufficient reflectivity at near vertical incidence to be compatible with long-period observations for waves traveling steeply in the mantle.