Dynamic slab segmentation due to brittle-ductile damage in the outer rise
Dynamic slab segmentation due to brittle-ductile damage in the outer rise
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DOI：
10.1038/s41586-021-03937-x
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发表时间：
2021-11-11
期刊：
影响因子：
64.8
通讯作者：
Becker, T. W.
中科院分区：
文献类型：
--
作者：
Gerya, T., V;Bercovici, D.;Becker, T. W.
板块俯冲是板块运动的主要驱动力，俯冲板块的强度控制着地球热化学演化的许多方面。每个俯冲板块在弯曲过程中经历强烈的正断层（1-9），这适应了海沟外部隆起处从水平运动到向下运动的过渡。在这里，我们调查的后果，这种弯曲引起的板损伤使用数值俯冲模型，其中脆性和韧性变形，包括晶粒损伤，跟踪和耦合自洽。由于脆性和韧性损伤局部化之间的强烈反馈，普遍的板弱化和明显的分割可以发生在外部隆起区域。这种板块损伤现象解释了强板块和弱板块（10）的俯冲二分法、海沟附近大偏移正断层（6、7）的发展、分段地震速度异常（11）的出现和俯冲板块（12、13）内清晰界面的成像，以及在海沟处观察到的有效粘度降低的深层局部板内区域（14）的出现。此外，脆性粘性损伤板片表现出在地幔温度升高时分离的趋势。考虑到地球的行星冷却历史（15），这意味着间歇性俯冲和频繁的板块断裂事件（16）可能是地球的特征，直到比以前提出的更近的时间（17）。用于确定弯曲引起的板块损伤后果的数值俯冲模型表明，板块弱化和分割可能发生在俯冲板块的外部隆起区域。
Subduction is the major plate driving force, and the strength of the subducting plate controls many aspects of the thermochemical evolution of Earth. Each subducting plate experiences intense normal faulting(1-9) during bending that accommodates the transition from horizontal to downwards motion at the outer rise at trenches. Here we investigate the consequences of this bending-induced plate damage using numerical subduction models in which both brittle and ductile deformation, including grain damage, are tracked and coupled self-consistently. Pervasive slab weakening and pronounced segmentation can occur at the outer-rise region owing to the strong feedback between brittle and ductile damage localization. This slab-damage phenomenon explains the subduction dichotomy of strong plates and weak slabs(10), the development of large-offset normal faults(6,7) near trenches, the occurrence of segmented seismic velocity anomalies(11) and distinct interfaces imaged within subducted slabs(12,13), and the appearance of deep, localized intraplate areas of reduced effective viscosity(14) observed at trenches. Furthermore, brittle-viscously damaged slabs show a tendency for detachment at elevated mantle temperatures. Given Earth's planetary cooling history(15), this implies that intermittent subduction with frequent slab break-off episodes(16) may have been characteristic for Earth until more recent times than previously suggested(17).Numerical subduction models used to determine the consequences of bending-induced plate damage show that slab weakening and segmentation can occur at the outer-rise region of the subducting plate.