地球内核的缓慢微分旋转是由散射的时间变化所表明的
1Department of Earth and Space Sciences, and Institute of Geophysics and Planetary Physics, University of California, Los Angeles 90095, USA. vidale@ucla.edu
Nature
|June 6, 2000
概括
地球内核的旋转是微妙的,但可以检测到. 新的地震数据表明,每年0.15度的旋转率差异,与以前的约束保持一致,并提供了对地力学的见解.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 地球科学 地球科学 地球科学
背景情况:
- 地球内核与地幔相对的旋转对地力学和地力学有重大影响.
- 以前的研究表明差分旋转,但由于地震数据的局限性和潜在偏差而面临挑战.
研究的目的:
- 用分散的地震波来研究内核运动.
- 为了提供更直接的内核微分旋转测试.
主要方法:
- 在地球内核中分散的地震波的分析.
- 在美国蒙大拿州记录的诺瓦亚泽姆利亚两次核试验 (1971年和1974年) 的分散波数据的比较.
主要成果:
- 观测到地震波散射中的小而连贯的变化.
- 表示内核的微分旋转速率为每年0.15度.
结论:
- 这些发现支持内部核心微分旋转的存在.
- 估计的旋转速率与自由振荡数据的约束相一致,并解决了以前的不确定性.
相关概念视频
Gyroscope: Precession
6.0K
Precession can be demonstrated effectively through a spinning top. If a spinning top is placed on a flat surface near the surface of the Earth at a vertical angle and is not spinning, it will fall over due to the force of gravity producing a torque acting on its center of mass. However, if the top is spinning on its axis, it precesses about the vertical direction, rather than topple over due to this torque. Precessional motion is a combination of a steady circular motion of the axis and the...
6.0K
Apparent Weight and the Earth's Rotation
4.5K
Since all objects on the Earth's surface move through a circle every 24 hours, there must be a net centripetal force on each object, directed towards the center of that circle. The points of the north and south poles are the only exception to this rule.
For an object on the Earth's equator, the net centripetal force that accounts for its rotation is the Earth's pull towards its center, or the weight minus the normal force that prevents it from piercing into the Earth's surface....
For an object on the Earth's equator, the net centripetal force that accounts for its rotation is the Earth's pull towards its center, or the weight minus the normal force that prevents it from piercing into the Earth's surface....
4.5K
Variation in Acceleration due to Gravity near the Earth's Surface
3.0K
An object's apparent weight is its weight measured by a spring balance at its location. It is different from its true weight, the force with which the Earth pulls it, because of the Earth's rotation. Mathematically, an object's apparent weight equals its true weight minus the centripetal force that keeps it in a circular motion along with the Earth's surface every 24 hours.
The difference between the true and apparent weights is proportional to the square of the Earth's...
The difference between the true and apparent weights is proportional to the square of the Earth's...
3.0K
Atomic Nuclei: Larmor Precession Frequency
3.8K
The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession,...
3.8K
Coriolis Force
7.5K
An accelerating particle experiences a force equal to the mass multiplied by the acceleration in an inertial frame of reference. Consider a particle in a non-inertial frame of reference, such as a sliding ball on a rotating table. The acceleration of the ball in this rotating reference frame is different than in the intertial frame, which modifies its equation of motion. The fictitious forces acting additionally on a rotating frame of reference alter Newton's Second Law expression.
7.5K
Influence of Earth's Curvature and Atmospheric Refraction on Leveling
1.3K
During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference. When the line of sight is leveled, it remains perpendicular to the plumb line only at a single point. Beyond this, it deviates due to the Earth’s curvature, represented by the correction C. For a sight distance D, the deviation can be derived using the relationship:This relationship shows that the deviation increases quadratically with distance.
1.3K


