中国科学院大学侯泉林团队近日在模拟慢震背景下石英变形的分子动力学的研究中取得新进展。相关论文于2025年1月8日发表在《中国科学：地球科学》杂志上。

据了解，慢震是慢能量释放的主要机制，然而人们对其震源机制的研究尚无定论。以往研究主要集中在基于物理机制的摩擦规律上，并解释缓慢地震是由脆性断层引起的。然而，俯冲带慢震的震源强度和构造特征提供了塑性变形的证据。塑性变形在慢震震源机制中的作用是什么？机械化学研究表明，机械力可以直接影响化学键。

在这里，本研究考察了塑性变形过程中化学能的储存和释放，并考虑了慢震震源机制中的一个力学化学过程。研究人员结合Tersoff势，对两种α-石英晶体剪切变形过程进行分子动力学模拟，结果表明α-石英的剪切模量为18GPa，晶体模型主要表现为原子在稳态流动阶段的流动和化学键方向的变化。剪切过程中分子势能和应力呈上下振荡曲线变化，表明在塑性变形过程中化学能可以储存和释放。这与慢震时的能量变化是一致的。

此外，在初始单剪切加载条件下，α-石英晶体发生一般性剪切变形而非平面应变，其最长瞬时拉伸轴（ISA₁）与剪切方向夹角约为30°，而非45°。ISA₁的变形类型和方向都与基本的变形理论相反，这可能为今后的研究提供线索。本研究揭示了石英在原子尺度上的弹塑性剪切变形过程。这一信息对理解慢震的震源机制很有帮助。本研究是构造应力化学系列研究的一部分。

附：英文原文

Title: Molecular dynamics simulation of quartz deformation under slow earthquake background

Author: Jingxian SUN, Qianqian GUO, Quanlin HOU

Issue&Volume: 2025/01/08

Abstract: Slow earthquakes are the primary mechanism of slow energy release, and research on the focal mechanism has been inconclusive. Studies have primarily focused on the friction law based on physical mechanisms and have suggested that slow earthquakes are caused by brittle faults. However, the focal strength and structural characteristics of slow earthquakes in subduction zones provide evidence of plastic deformation. What is the role of plastic deformation in the focal mechanisms of slow earthquakes Mechanochemical study have shown that mechanical forces can directly affect chemical bonds. In this study, we examine the storage and release of chemical energy during plastic deformation and consider a mechanochemical process in the focal mechanism of slow earthquakes. Combined with the Tersoff potential, molecular dynamics simulation on the shear deformation process of two α-quartz crystals show that the shear modulus of α-quartz is 18GPa, and that the crystal model primarily exhibits atoms flowing and changing in the direction of chemical bonds during the steady-state flow stage. The molecular potential energy and stress vary in an oscillating up-and-down curve during shear, indicating that chemical energy can be stored and released during plastic deformation. This is consistent with the energy variation during slow earthquakes. Under the initial simple-shear loading condition, α-quartz crystals undergo general shear deformation instead of plane strain and the angle between the longest instantaneous stretching axis (ISA₁) and the shearing direction is approximately 30°, not 45°. Both the deformation type and direction of ISA₁ are contrary to basic deformation theory, which may provide clues for future research. This study reveals the process of quartz elastic-plastic shear deformation on an atomic scale. This information is useful for understanding focal mechanisms of slow earthquakes. This study is part of a series of investigations on tectonic stress chemistry.

DOI: 10.1007/s11430-024-1469-0

Source: https://www.sciengine.com/SCES/doi/10.1007/s11430-024-1469-0