Quantifying fault damage zones provides a window into stress distribution and rheology around faults. International Ocean Discovery Program (IODP) Expeditions 372/375 drilled an active thrust splay fault within the Hikurangi subduction margin. The fault, which is hosted in Pleistocene clastic sediments, is surrounded by brittle fractures and faults as well as ductile deformation features. We find that fracture density in the damage zone enveloping the fault is asymmetric, with the hanging wall showing greater overall fracture density and at greater distances from the fault than the footwall. Furthermore, the peak in fracture density occurs within an area of mesoscale folding and localized slip in the hanging wall rather than adjacent to the main fault zone. We attribute the asymmetry in damage to disparate deformation histories between the hanging wall and footwall, greater ductile deformation within the footwall, and/or dynamic stress asymmetry around a propagating rupture. Damage asymmetry is common at shallow depths in subduction zones and influences the mechanical and hydrological properties of the fault, such as channelized fluid flow and fault stability. Finally, we demonstrate that subduction zone faults show similar damage-displacement scaling as continental faults.

中文翻译：

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新西兰 Hikurangi 俯冲边缘 Pāpaku 断层的不对称脆性变形，IODP Expedition 375

量化断层损伤区为了解断层周围的应力分布和流变学提供了一个窗口。国际海洋发现计划 (IODP) 探险队 372/375 在 Hikurangi 俯冲边缘内钻探了一个活跃的逆冲张开断层。该断层位于更新世碎屑沉积物中，周围环绕着脆性断裂和断层以及韧性变形特征。我们发现包围断层的损伤带中的裂缝密度是不对称的，与下盘相比，上盘显示出更大的整体裂缝密度并且与断层的距离更大。此外，裂缝密度的峰值出现在上盘中尺度褶皱和局部滑动的区域内，而不是在主断层带附近。我们将损坏的不对称性归因于上墙和下盘之间不同的变形历史、下盘内更大的延展性变形和/或围绕传播破裂的动态应力不对称。破坏不对称在俯冲带的浅层很常见，并影响断层的力学和水文特性，如通道化流体流动和断层稳定性。最后，我们证明俯冲带断层显示出与大陆断层相似的破坏位移比例。