Molecular dynamics simulation of quartz deformation under slow earthquake background  

作　　者：Jingxian SUN Qianqian GUO Quanlin HOU 

机构地区：[1]College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Key Laboratory of Computational Geodynamics,CAS,Beijing 100049,China

出　　处：《Science China Earth Sciences》2025年第2期598-610,共13页中国科学(地球科学英文版)

基　　金：supported by the National Natural Science Foundation of China(Grant No.42220104008);the University of Chinese Academy of Sciences(Grant No.E3JT040103)。

摘　　要：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 twoα-quartz crystals show that the shear modulus ofα-quartz is 18 GPa,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(ISA_(1))and the shearing direction is approximately 30°,not 45°.Both the deformation type and direction of ISA_(1)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.

关 键 词：Slow earthquake α-quartz Plastic strain energy Tectonic stress chemistry Tersoff potential 

分 类 号：P31[天文地球—固体地球物理学]