16:15 〜 16:30
[SCG40-19] Impacts of rheological variations along plate boundary in subduction zones for deep slow earthquakes
キーワード：プレート境界、沈み込み帯、数値シミュレーション、レオロジー変化
Deep tremor and slow slip events are thought to occur in transition zones where brittle and ductile domains coexist. The coexistence of such complex, different rheologies is thought to result from the presence of different materials along the plate boundary. However, the behavior of the materials present along the plate boundary is not fully understood. For example, recent studies suggest that the strength of the hydrous oceanic crust may be less than previously thought. These observations underscore the importance of studying how variations in material properties at the plate boundary influence its structure. In this talk, numerical simulations using a thermomechanical code are used to investigate the effect of rheological variations in materials such as sediments and oceanic crust on the structure of the plate interface.
In the simulation, the plate boundary fault consists mainly of sediments and oceanic crust. The materials that contribute to shear deformation along the plate boundary fault vary with depth. At shallow depths, sediments contribute most of the shear deformation (Stage I). With increasing depth, the oceanic crust begins to participate in shear deformation, but sediments continue to account for most of the deformation (Stage II). At deeper levels, both oceanic crust and sediments contribute almost equally to shear deformation (Stage III). In particular, the situation where different materials jointly bear deformation, with different amounts of deformation borne by each material (Stage II), is similar to the deformation structures observed in the Deep Tremor Zone with block-in-matrix structures: the material comprising the matrix is largely sheared with ductile deformation, while the material comprising the block is slightly sheared with brittle deformation. Furthermore, changing the strength of the oceanic crust changes the depth at which Stage II occurs. In fact, as the strength of the oceanic crust increases, the depth of Stage II becomes deeper. This suggests that the formation depth of the block-in-matrix structures observed in the Deep Tremor Zone may vary depending on the properties of the material that forms it (in this case, the oceanic crust).
In the simulation, the plate boundary fault consists mainly of sediments and oceanic crust. The materials that contribute to shear deformation along the plate boundary fault vary with depth. At shallow depths, sediments contribute most of the shear deformation (Stage I). With increasing depth, the oceanic crust begins to participate in shear deformation, but sediments continue to account for most of the deformation (Stage II). At deeper levels, both oceanic crust and sediments contribute almost equally to shear deformation (Stage III). In particular, the situation where different materials jointly bear deformation, with different amounts of deformation borne by each material (Stage II), is similar to the deformation structures observed in the Deep Tremor Zone with block-in-matrix structures: the material comprising the matrix is largely sheared with ductile deformation, while the material comprising the block is slightly sheared with brittle deformation. Furthermore, changing the strength of the oceanic crust changes the depth at which Stage II occurs. In fact, as the strength of the oceanic crust increases, the depth of Stage II becomes deeper. This suggests that the formation depth of the block-in-matrix structures observed in the Deep Tremor Zone may vary depending on the properties of the material that forms it (in this case, the oceanic crust).