講演情報
[PPS04-P36]Two dimensional numerical experiments of mantle convection with stress-history-dependent rheology: Toward understanding the tectonics of terrestrial bodies
*田井東 大貴1、亀山 真典2,3 (1.愛媛大学大学院 理工学研究科 、2.愛媛大学 地球深部ダイナミクス研究センター、3.愛媛大学 先端研究院)
キーワード：
マントル対流、数値計算、応力履歴依存レオロジー、ひずみ速度弱化
In this study we develop a numerical model of the deformation of the stiff lithospheres at the cold surfaces of terrestrial bodies, as part of our ongoing endeavor aiming at self-consistent reproduction of plate tectonics within a framework of numerical simulations on mantle convection. The new numerical model is an extension of the earlier one in Taito et al. (2025), by imposing a horizontal deformation -either extensional or compressional- at the surface layer. The key of our experiments lies in the stress-history-dependent rheology (Ogawa, 2003; Miyagoshi et al., 2020). This rheology model, which closely mimics a universal property of rocks, allows the coexistence of weak regions with intense localized deformations (e.g., faults, plate boundaries) and stiff regions with minimal deformation (e.g., plates) at the surface of terrestrial bodies. By carrying out calculations using various states of deformation (such as extension or compression) applied to the models, we examine the link between the surface tectonics on terrestrial bodies and the initiation and progression of "damage" in the highly viscous lithosphere that forms ubiquitously in cold near-surface regions. Our preliminary calculations showed that the horizontal spacings of initially generated "damaged" zones, as well as those of well-developed ones similar to faults, vary depending on the mechanical states of the cold lithospheres, particularly on the depth ranges of the "strain-rate weakening" where the stress decreases with increasing strain-rate. These results suggest an ultimate importance of the "strain-rate weakening" in the progression of "damage" leading to the localization of deformation.