Subducted slabs stagnant above, penetrating through, and trapped below the 660 km discontinuity
Subducted slabs stagnant above, penetrating through, and trapped below the 660 km discontinuity
复制标题
DOI：
10.1002/2013jb010466
复制
发表时间：
2013-11-01
影响因子：
3.9
通讯作者：
Obayashi, Masayuki
中科院分区：
文献类型：
--
作者：
Fukao, Yoshio;Obayashi, Masayuki
利用1000多万次的旅行时间建立了一个新的地幔P波层析成像模型。考虑到地震射线的有限频率效应，对所有初至时数据计算了2 Hz的香蕉核，对宽频带旅行时差分数据计算了0.1Hz的香蕉核。基于这个模型，一个系统的调查俯冲板片图像开发的环太平洋，包括千岛群岛，本州，伊豆小笠原，马里亚纳群岛，爪哇，汤加Kermadec，南部和北方南美洲，中美洲，弧。该调查揭示了板片结构沿沿着弧的横向变化，我们将其解释为板片俯冲通过布伦过渡区的连续阶段的指示，中间有660 km的不连续面。我们确定了四个不同的阶段：I -板片停滞在660公里的不连续性; II -板片穿透660公里的不连续性; III -板片被困在下地幔的最上部（在660- 1000公里的深度）;和IV -板片下降到下地幔深处。发现大多数板图像处于第I或III阶段，这表明第I和III阶段相对稳定或中性，而第II和IV阶段相对不稳定或短暂。第一阶段板片与第二、三阶段板片的最深震源分布有明显区别。
A new P wave tomographic model of the mantle was constructed using more than 10 million travel times. The finite-frequency effect of seismic rays was taken into account by calculating banana-donut kernels at 2Hz for all first arrival time data, and at 0.1Hz for broadband differential travel time data. Based on this model, a systematic survey for subducted slab images was developed for the circum-Pacific; including the Kurile, Honshu, Izu-Bonin, Mariana, Java, Tonga-Kermadec, southern and northern South America, and Central America, arcs. This survey revealed a progressive lateral variation of the configuration of slabs along arc(s), which we interpret as an indication for successive stages of slab subduction through the Bullen's transition region with the 660km discontinuity at the middle. We identified the four distinct stages: I - slab stagnant above the 660km discontinuity; II - slab penetrating the 660km discontinuity; III - slab trapped in the uppermost lower mantle (at a depth of 660-1000km); and IV - slab descending well into the deep lower mantle. The majority of slab images are found to be either at Stage I or III, suggesting that Stages I and III are relatively stable or neutral and II and IV are relatively unstable or transient. There is a remarkable distinction for the deepest hypocentral distribution between slabs at Stage I and slabs at Stages II or III.