Du Shuyuan, Cao Jingpu, Zhou Shihong, Qi Yubo, Jiang Lei, Zhang Yongfeng, Qiao Changcheng
State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China.
The 27th Research Institute of China Electronics Technology Group Corporation, Zhengzhou 450047, China.
J Acoust Soc Am. 2020 Dec;148(6):3992. doi: 10.1121/10.0002949.
Very-low-frequency (VLF) sound has significant potential for underwater detection and estimation of geoacoustic models of the ocean bottom structure. In marine settings, one type of VLF sound is the interface wave. These waves, trapped near the fluid-solid interface, are called Scholte waves, and this is the subject of this study. A field experiment was carried out in the South China Sea with the objective of exciting Scholte waves and investigating the propagation. The data were acquired by an ocean bottom seismometer, deployed on the seafloor. A large volume airgun array near the sea surface provided the sound source. The fundamental and three higher-order mode Scholte waves were excited. The Scholte waves are investigated by seismograms and a phase velocity inversion. The observed frequencies are in the range of 1.0-2.9 Hz. The energy attenuation is proportional to 1/r at the peak frequency 1.4 Hz. The shear wave speed structure, down to 600 m beneath the seafloor, is revealed from the dispersion curves by a least-squares inversion algorithm. The inversion result shows that the shear wave speed is below 300 m/s in the uppermost layer, which explains well the weak excitation of Scholte waves in this experiment.
甚低频（VLF）声音在水下探测以及海底结构地声学模型估计方面具有巨大潜力。在海洋环境中，一种甚低频声音是界面波。这些被困在流体 - 固体界面附近的波被称为肖尔特波，这也是本研究的主题。在南海进行了一项野外实验，目的是激发肖尔特波并研究其传播情况。数据由部署在海底的海底地震仪采集。海面附近的一个大容量气枪阵列提供声源。激发了基模和三个高阶模式的肖尔特波。通过地震图和相速度反演对肖尔特波进行研究。观测频率在1.0 - 2.9赫兹范围内。在峰值频率1.4赫兹处，能量衰减与1/r成正比。通过最小二乘反演算法从频散曲线中揭示了海底以下600米深度范围内的剪切波速度结构。反演结果表明，最上层的剪切波速度低于300米/秒，这很好地解释了本实验中肖尔特波激发较弱的现象。
