Yokoyama Hiroaki, Ofune Tomu, Jayawickrama Eranga, Hirano Mitsuhiro, Sawa Sando, Muto Jun, Nagahama Hiroyuki
Department of Earth Sciences, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan.
SIGMAXYS Holdings Inc., Minato-Ku, Tokyo, Japan.
Sci Rep. 2025 Sep 26;15(1):33203. doi: 10.1038/s41598-025-17812-6.
Kink bands are localized folds or bends formed in layered materials, such as millefeuille. They are common in rocks within the earth's crust that have undergone compression deformation. While the formation of kinks has been studied extensively, their effects on material strength remain unclear in geologic materials. This study investigates the relationship between kink formation and compressive strength through experiments on crustal-material biotite. In our results, kink bands are observed pervasively in samples and show hardening behavior. The observed kinks have symmetric tilt boundaries, satisfying the rank-1 connection condition, a key condition for material strengthening. Therefore, the hardening behavior observed in this study is due to "kink strengthening". Furthermore, we reviewed whether kink bands of various scales in geologic materials satisfy the rank-1 connection and discussed its effect on the strength. Notably, it is indicated that the formation of mega kinks (km-scale kinks) strengthens the crust and influences earthquake rupture.
扭折带是在千层饼状等层状材料中形成的局部褶皱或弯曲。它们在地壳中经历压缩变形的岩石中很常见。虽然扭折的形成已得到广泛研究，但它们对地质材料强度的影响仍不清楚。本研究通过对地壳物质黑云母进行实验，研究了扭折形成与抗压强度之间的关系。在我们的结果中，扭折带在样品中普遍观察到，并表现出硬化行为。观察到的扭折具有对称的倾斜边界，满足一级连接条件，这是材料强化的关键条件。因此，本研究中观察到的硬化行为是由于“扭折强化”。此外，我们还回顾了地质材料中不同尺度的扭折带是否满足一级连接，并讨论了其对强度的影响。值得注意的是，研究表明巨型扭折（千米尺度扭折）的形成会强化地壳并影响地震破裂。
