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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The 660-km discontinuity within the subducting NW-Pacific lithospheric slab
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The 660-km discontinuity within the subducting NW-Pacific lithospheric slab

机译：俯冲西北太平洋岩石圈平板内660公里的不连续性

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摘要

The 660-km seismic discontinuity (660) in Earth's mantle is generally attributed to the breakdown of the rinwoodite phase of olivine, but other mineral reactions are also thought to occur near 660-km depth. Recently, complex arrivals of P660s waves (converted from P to s at the 660) in active and recently active subduction zones have been interpreted as evidence for additional seismic discontinuities caused by the garnet-perovskite and garnetilmenite-perovskite phase transformations (gt → pv, gt → il → pv) at relatively low temperatures. Here we show that the P660s phases converting at the 660 within the subducting NW-Pacific slab beneath the station MDJ in Northeast China are clear and coherent, with no additional arrivals in the vicinity. P660s waves that convert near the boundaries of the area where the 660 occurs within the slab produce distinctly more complex, multiple arrivals, but they are more likely to be caused by small-scale topography rather than 'multiplicity' of the 660. Our observations suggest that the gt → pv transformation and the gt → il → pv, if it occurs in the mantle, are spread over tens of kilometers and do not have sharp onsets visible to short-period seismic waves.
机译：地球地幔中660 km的地震不连续性（660）通常归因于橄榄石的rinwoodite相的破裂，但其他矿物反应也被认为在660 km深度附近发生。最近，在活跃的和最近活跃的俯冲带中，P660s波的复杂到达（在660处从P转换为s）已被解释为由石榴石-钙钛矿和石榴石-钙钛矿相变（gt→pv， gt→il→pv）在相对较低的温度下。在这里，我们表明，在东北东北部MDJ站下方的俯冲西北太平洋板块中660处的P660s相变是清晰且连贯的，附近没有其他到达。在板中660发生区域的边界附近转换的P660s波产生明显更复杂的多次到达，但它们更可能是由小规模地形引起的，而不是660的“多重性”。我们的观察表明如果gt→pv变换和gt→il→pv发生在地幔中，则它们会散布数十公里，并且对于短周期地震波没有明显的爆发。

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