The sources of shallow slow earthquakes at subduction zone fronts remain unclear, but are commonly attributed to faults and shear zones. Structural studies of modern and ancient shallow accretionary prisms — wedge-shaped stacks of sediments and volcanic deposits scraped from subducting slabs and accreted onto the overriding plates at convergent plate boundaries — document a plethora of brittle structures associated with metres to plurikilometre-scale overturned and recumbent folds. These folds are the product of rock buckling and shearing at the front of subduction zones. At present, such structures are not commonly considered in models of the dynamics of accretionary wedges at the timescale of the seismic cycle, instead focusing on the role played by slip on major faults. Here we argue that fold-related brittle structures might also be associated with transient deformation events at elevated strain rates and in the presence of high fluid pressure. They have the potential to cause distributed microearthquake swarms occurring under low effective normal stress in accretionary prisms, and to affect the distribution of surficial displacement.

俯冲带前缘浅源慢震的来源尚不清楚，但通常归因于断层和剪切带。对现代和古代浅层增生棱柱的结构研究——从俯冲板片上刮下的楔形沉积物和火山沉积物堆积到会聚板块边界的覆盖板块上——记录了大量与米到千里尺度的翻转和横卧相关的脆性结构褶皱。这些褶皱是俯冲带前部岩石屈曲和剪切的产物。目前，在地震周期时间尺度的增生楔动力学模型中，通常不考虑此类结构，而是将重点放在主要断层上滑动所起的作用。在这里，我们认为，与折叠相关的脆性结构也可能与高应变率和高流体压力下的瞬态变形事件有关。它们有可能在增生棱柱的低有效法向应力下引起分布式微震群的发生，并影响地表位移的分布。