地球の内核の微細なスケールの異質性
1Earth and Space Science Department and Institute of Geophysics and Planetary Physics, University of California at Los Angeles, 90095-1567, USA. vidale@ucla.edu
Nature
|April 5, 2000
まとめ
地震波の散乱は,地球の固体内核の硬さの変動を明らかにする. これらの発見は,核の外層内の構成またはアニソトロピーの潜在的な変化を示唆しています.
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:
- 地球の内核の地震学的性質は,その構成と熱状態を理解するために重要である.
- アニゾトロピーと速度の異質性は,内核の成長とコンベクションを示唆する.
- 内核の高い地震波減衰は,散乱または固有減衰に起因する.
研究 の 目的:
- 地球の内核内の地震波の散乱を調査するために.
- 予想される反射時間に達する分散した地震波の特性を分析する.
- 散乱振幅に基づいて内核の最も外側の層の性質を推論する.
主な方法:
- 内核内に散らばった地震波の観測.
- 内核境界からの地震波反射の分析.
- 硬さの変動を決定するために分散波幅のモデリング.
主要な成果:
- 観測された分散した地震波は,内核境界からの体波反射と一致する.
- 散らばった波幅は,2kmのスケール長で1.2%の硬さの変動によって説明される.
- これらの変異は,内核の最も外側の300km以内に位置しています.
結論:
- 内核の最も外側の300kmは,著しい硬さの変動を示している.
- これらの変動は,組成の変化,部分溶解,または地震性アニソトロピーを示す可能性があります.
- 散乱分析は,内核の構造と動態に関する新しい洞察を提供します.
さらに関連する動画
11:50Metal-silicate Partitioning at High Pressure and Temperature: Experimental Methods and a Protocol to Suppress Highly Siderophile Element Inclusions
Published on: June 13, 2015
12.0K
09:13Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction
Published on: April 1, 2017
14.8K
関連する概念動画
Isothermal Processes
3.8K
A thermodynamic process that occurs at constant temperature is called an isothermal process. Heat slowly flows into the system or out of the system to maintain thermal equilibrium. Processes involving phase changes like water evaporation into steam or freezing water into ice at a constant temperature are examples of Isothermal Processes.
An ideal gas can also undergo isothermal expansion or compression.
For example, consider 1 mole of an ideal gas inside an isolated cylinder at initial volume V...
An ideal gas can also undergo isothermal expansion or compression.
For example, consider 1 mole of an ideal gas inside an isolated cylinder at initial volume V...
3.8K
Ferromagnetism
2.8K
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
2.8K
Magnetic Susceptibility and Permeability
2.9K
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...
2.9K
Fineness of Cement
814
The fineness of cement directly influences the rate of hydration, as the hydration begins at the surface of the cement particles. In addition to hydration, the fineness of cement is vital for various properties of concrete including workability, gypsum requirement, and long-term behavior. The fineness of cement is represented in terms of the specific surface of cement which is typically measured in square meters per kilogram, with several methods available for this determination.
Direct...
Direct...
814
Fineness Modulus
2.0K
The fineness modulus (FM) of aggregate is a numerical index that measures the coarseness or fineness of the particles. It is calculated by adding the cumulative percentages of aggregate retained on each of a specified series of sieves and dividing the sum by 100.
Consider performing sieve analysis on sand through a set of ASTM sieves. The weight of aggregate retained in each sieve and pan placed at the bottom is recorded, as given in Column B of Table 1.
To determine the fineness modulus of...
Consider performing sieve analysis on sand through a set of ASTM sieves. The weight of aggregate retained in each sieve and pan placed at the bottom is recorded, as given in Column B of Table 1.
To determine the fineness modulus of...
2.0K
Pore Size Distribution
691
In concrete, the pore size distribution significantly influences the material's properties. Capillary pores, markedly larger than gel pores, form a vast network within partially hydrated cement paste, reducing the concrete's strength and increasing its permeability. This heightened permeability leads to a greater risk of damage from environmental factors like freeze-thaw cycles and chemical attacks, with the extent of vulnerability also being tied to the water-to-cement ratio.
Adequate...
Adequate...
691
