Ye Sheng Hua, Lui Semechah K Y, Young R Paul
Civil and Mineral Engineering, University of Toronto, 35 St. George St, Toronto, ON, M5S 1A4, Canada.
Chemical and Physical Sciences, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON, L5L 1C6, Canada.
Sci Rep. 2024 Nov 21;14(1):28812. doi: 10.1038/s41598-024-80136-4.
Understanding earthquake nucleation is vital for predicting and mitigating seismic events, saving lives, and enhancing construction practices in earthquake-prone areas. Cascade triggering and preslip triggering are prevalent theories, posing challenges in differentiation based on field observations. Our study employs a novel unsupervised machine learning pipeline, integrating macroscopic- and grain-scale data from stick-slip experiments in a discrete element method (DEM) framework. Running 27 simulations, we cluster foreshocks and mainshocks separately and assess their correlation. The study supports the cascade triggering model on the macro-scale, as we did not observe any scaling between nucleation parameters and the mainshock size. On the other hand, further grain-scale analysis identifies that, separate from Coulomb stress transfer, there is an additional mechanism related to shear stress accumulation on the fault, which is likely the preslip triggering. Overall, while foreshocks may not directly influence the trend at which contact force evolves, they could prime the fault for dynamic rupture by increasing the proportion of contacts accumulating shear stresses. Our findings infer the possible coexistence of the two theorized mechanisms.
了解地震成核对于预测和减轻地震事件、拯救生命以及改进地震多发地区的建筑实践至关重要。级联触发和预滑动触发是普遍存在的理论，基于现场观测进行区分具有挑战性。我们的研究采用了一种新颖的无监督机器学习流程，在离散元方法（DEM）框架中整合了来自粘滑实验的宏观和颗粒尺度数据。运行27次模拟后，我们分别对前震和主震进行聚类并评估它们的相关性。该研究在宏观尺度上支持级联触发模型，因为我们没有观察到成核参数与主震规模之间存在任何标度关系。另一方面，进一步的颗粒尺度分析表明，除了库仑应力传递之外，在断层上还存在一种与剪应力积累相关的额外机制，这可能就是预滑动触发。总体而言，虽然前震可能不会直接影响接触力演变的趋势，但它们可能通过增加积累剪应力的接触比例使断层为动态破裂做好准备。我们的研究结果推断这两种理论机制可能共存。
