地震正常モード観測から内核アニソトロピーの地域変動
Arwen Deuss1, Jessica C E Irving, John H Woodhouse
1Department of Earth Sciences, University of Cambridge, Cambridge CB3 0EZ, UK. afd28@cam.ac.uk
まとめ
研究者は地震データを用いて地球の内核の半球アニソトロピーを発見しました. このパターンは,磁場と同様に,結晶の固化またはマクスウェルのストレス中に結晶の並び方を示唆し,内核の超回転を制限します.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 地震学 地震学とは
- 地球科学 地球科学 地球科学
背景:
- 地球の磁場は,液体外核のジオダイナモによって生成されます.
- 以前の地震研究は,内核アニソトロピーの半球的な変動を示唆したが,詳細な制約が欠けていた.
研究 の 目的:
- 地球の内核内の地域的および半球的アニソトロピーを調査する.
- 内核アニソトロピーの起源とそのジオダイナモとの関係を探求する.
主な方法:
- 大規模な地震からの正常モード分割機能測定を活用しました.
- 地震波の伝播を分析するために拡張クロスカップリング理論を適用した.
主要な成果:
- 内核アニソトロピーの明確な地域的変動が観察されました.
- 内核の東対西半球アニソトロピーを特定した.
- 地球の磁場と似たパターンを発見した.
結論:
- 内核のアニソトロピーは,固化またはマクスウェルのストレス中に結晶の整列から生じる可能性があります.
- この発見は,内核の超回転の範囲を制限し,振動モデルを支持している.
関連する概念動画
Elastic Strain Energy for Normal Stresses
Strain energy quantifies the energy stored within a material due to deformation under loading conditions, a fundamental concept in materials science and engineering. The strain energy can be modeled when a material is subjected to axial loading with uniformly distributed stress. In this scenario, the stress experienced by the material is the internal force divided by the cross-sectional area, and the strain induced is directly proportional to this stress through the modulus of elasticity.
If...
If...
Normal Strain under Axial Loading
Normal strain under axial loading is an important concept in the field of mechanics of materials. Axial loading implies the application of a force along the axis of a material, like a column or bar. This force can either compress or stretch the material. In the context of axial loading, normal strain is the deformation experienced by the material in the direction of the loading force. It's calculated as the change in length divided by the original length of the material. This unitless ratio...
Normal Stress
Normal stress is a type of stress that occurs when forces act perpendicular, or normal, to a material's cross-sectional area. This stress often arises in structures when subjected to axial loading, which is the application of force along the axis of an object. A practical example of this can be found in bridge truss members.
When a rod is under axial loading, the internal forces and corresponding stress are normal to the plane of the section, so it is termed normal stress. It's important to...
When a rod is under axial loading, the internal forces and corresponding stress are normal to the plane of the section, so it is termed normal stress. It's important to...
Magnetic Susceptibility and Permeability
In linear magnetic materials, like paramagnets and diamagnets, magnetization is proportional to the magnetic field intensity. The constant of proportionality, a dimensionless number, is called magnetic susceptibility. The value of the susceptibility depends on the type of material.
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
Elastic Strain Energy for Shearing Stresses
As discussed in previous lessons, strain energy in a material is the energy stored when it is elastically deformed, a concept crucial in materials science and mechanical engineering. This energy results from the internal work done against the cohesive forces within the material. When a material undergoes shearing stress and corresponding shearing strain, the strain energy density, which is the energy stored per unit volume, is calculated. Within the elastic limit, where the stress is...
Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
Deformation occurs in axial and transverse directions when an axial load is applied to a slender bar. This deformation impacts the cubic element within the bar, transforming it into either a rectangular parallelepiped or a rhombus, contingent on its orientation. This transformation process induces shearing strain. Axial loading elicits both shearing and normal strains. Applying an axial load instigates equal normal and shearing stresses on elements oriented at a 45° angle to the load axis.

