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^{1,2,3,4,5,6,7,8,9} 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 slabs¹⁰, the development of large-offset normal faults^6,7 near trenches, the occurrence of segmented seismic velocity anomalies¹¹ and distinct interfaces imaged within subducted slabs^12,13, and the appearance of deep, localized intraplate areas of reduced effective viscosity¹⁴ observed at trenches. Furthermore, brittle–viscously damaged slabs show a tendency for detachment at elevated mantle temperatures. Given Earth’s planetary cooling history¹⁵, this implies that intermittent subduction with frequent slab break-off episodes¹⁶ may have been characteristic for Earth until more recent times than previously suggested¹⁷.

俯冲是主要的板块驱动力，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都经历了强烈的正断层^{1、2、3、4、5、6、7、8、9}，以适应在沟槽外隆起处从水平运动到向下运动的过渡。在这里，我们使用数值俯冲模型研究了这种弯曲引起的板块损伤的后果，在该模型中，包括晶粒损伤在内的脆性和韧性变形都被跟踪和自洽地耦合。由于脆性和延性损伤定位之间的强烈反馈，外层区域可能会出现普遍的板坯弱化和明显的分割。这种板块损伤现象解释了强板块和弱板块的俯冲二分法^{如图 10}所示，在海沟附近出现了大断距正断层^6,7 ，在俯冲板块^{12,13内出现了分段的地震速度异常11}和成像的明显界面 12,13 ，以及观察到有效粘度降低的深层局部板内区域¹⁴的出现在战壕里。此外，脆性粘性损坏的板片在升高的地幔温度下显示出分离的趋势。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片断裂事件¹⁶可能一直是地球的特征，直到比之前建议的¹⁷更晚。