概括
地震数据显示,夏威夷下方有一个深层地幔羽毛,证据是上层地幔的低剪波速度和稀薄的过渡区. 这表明夏威夷羽毛的更热,更低的地幔起源.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 地幔动态地幔动态
背景情况:
- 据认为,夏威夷群岛是由海洋石质层在地幔热点上移动而形成的.
- 地化学和重力数据表明存在热,但缺乏直接的地震证据.
研究的目的:
- 为夏威夷地幔羽毛提供直接的地震证据.
- 研究夏威夷海底上层地幔的结构和热状态.
主要方法:
- 对压缩到剪切 (P-to-S) 地震转换相的分析.
- 在夏威夷群岛的地震仪站记录地震数据.
主要成果:
- 在夏威夷海底130-140公里深处确定了一个极低剪切波速度 (<4公里/秒) 的区域.
- 观察到上层地幔过渡区 (410-660公里) 在夏威夷的西南南部变薄.
- 估计天气层的温度超过300°C,夏威夷羽毛的温度比冰岛羽毛高100°C.
结论:
- 地震观测证实了夏威夷风云管道存在于天层和地幔过渡区.
- 过渡区的显著稀薄表明夏威夷羽毛的下层地幔起源,类似于冰岛羽毛.
相关概念视频
Travelling Waves
A wave is a disturbance that propagates from its source, repeating itself periodically, and is typically associated with simple harmonic motion. Mechanical waves are governed by Newton's laws and require a medium to travel. A medium is a substance in which a mechanical wave propagates, and the medium produces an elastic restoring force when it is deformed.
Water waves, sound waves, and seismic waves are some examples of mechanical waves. For water waves, the wave propagation medium is water;...
Water waves, sound waves, and seismic waves are some examples of mechanical waves. For water waves, the wave propagation medium is water;...
Interference and Superposition of Waves
When two waves of the same nature occur in the same region simultaneously, they result in interference. Interference of waves implies that the net effect of the waves is the sum of the individual waves' effects. However, it does not imply that the individual waves affect the propagation of other waves.
Interference occurs in mechanical waves, such as sound waves, waves on a string, and surface water waves. Mechanical waves correspond to the physical displacement of particles. Hence,...
Interference occurs in mechanical waves, such as sound waves, waves on a string, and surface water waves. Mechanical waves correspond to the physical displacement of particles. Hence,...
Propagation of Waves
When a wave propagates from one medium to another, part of it may get reflected in the first medium, and part of it may get transmitted to the second medium. In such a case, the interface of the two mediums can be considered as a boundary that is neither fixed nor free.
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
Shock Waves
While deriving the Doppler formula for the observed frequency of a sound wave, it is assumed that the speed of sound in the medium is greater than the source's speed through it. When this condition is breached, a shock wave occurs.
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high pressures...
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high pressures...
Plane Electromagnetic Waves II
Consider a plane wavefront traveling in position x-direction with a constant speed. This wavefront can be utilized to obtain the relationship between electric and magnetic fields with the help of Faraday's law.
Standing Waves in a Cavity
A household microwave and lasers are examples of standing electromagnetic waves in a cavity. When two conducting metal plates are placed parallel at the nodal planes, it creates a cavity where standing waves are formed. The cavity between the two planes is analogous to a stretched string held at the points x = 0 and x = L. Here, the distance 'L' between the two planes must be an integer multiple of half of the wavelength. The wavelengths that satisfy this condition are given by:


