arXivDaily arXiv每日学术速递 周一至周五更新
北美退伍军人节(Veterans Day),12 日无更新
arXiv 1209.5015physics.ao-ph
收藏

有限深度内非线性相互作用表面重力波在固体地球、海洋和大气中产生的噪声

Noise generation in the solid Earth, oceans, and atmosphere, from non-linear interacting surface gravity waves in finite depth

Fabrice Ardhuin, Thomas H. C. Herbers

摘要:

海洋压力测量,即使在非常深的水中,以及来自地球上任何地方的大气压力或地震记录,都包含主要周期在3秒和10秒之间的噪声,据信这些噪声是由海洋表面重力波激发的。这种噪声的大部分由非线性波-波相互作用机制来解释,并采取表面重力波、声波或地震波的形式。以前的理论工作地震噪声集中在表面(瑞利)波,并没有考虑有限深度的影响,产生波运动学。这些有限深度的影响在这里介绍,这需要考虑的直接波在海底引起的压力,以前被忽视的背景下的地震噪声的贡献。这种贡献可以导致地震噪声源的显著减少,这对于大于10 s的噪声周期特别相关。该理论适用于大气中的声波,扩展了以前仅限于垂直传播的理论。最后,将噪声产生理论推广到瑞利波以外,首次给出了地震体波源的定量表达式。在慢相速度的海浪强迫的限制,得到已知的和验证良好的重力波的结果,这是以前推导出的不可压缩的海洋。声学、声重力和地震模式的噪声源由零波数附近相同波致压力场的特定模式放大给出。

英文摘要:

Oceanic pressure measurements, even in very deep water, and atmospheric pressure or seismic records, from anywhere on Earth, contain noise with dominant periods between 3 and 10 seconds, that is believed to be excited by ocean surface gravity waves. Most of this noise is explained by a nonlinear wave-wave interaction mechanism, and takes the form of surface gravity waves, acoustic or seismic waves. Previous theoretical works on seismic noise focused on surface (Rayleigh) waves, and did not consider finite depth effects on the generating wave kinematics. These finite depth effects are introduced here, which requires the consideration of the direct wave-induced pressure at the ocean bottom, a contribution previously overlooked in the context of seismic noise. That contribution can lead to a considerable reduction of the seismic noise source, which is particularly relevant for noise periods larger than 10 s. The theory is applied to acoustic waves in the atmosphere, extending previous theories that were limited to vertical propagation only. Finally, the noise generation theory is also extended beyond the domain of Rayleigh waves, giving the first quantitative expression for sources of seismic body waves. In the limit of slow phase speeds in the ocean wave forcing, the known and well-verified gravity wave result is obtained, which was previously derived for an incompressible ocean. The noise source of acoustic, acoustic-gravity and seismic modes are given by a mode-specific amplification of the same wave-induced pressure field near the zero wavenumber.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑