Observation and inversion of very-low-frequency seismo-acoustic fields in the South China Sea
Observation and inversion of very-low-frequency seismo-acoustic fields in the South China Sea
复制标题
南海甚低频地震声场观测与反演.
DOI：
10.1121/10.0002949
复制
发表时间：
2020-12-01
影响因子：
2.4
通讯作者：
Qiao, Changcheng
中科院分区：
文献类型：
--
作者：
Du, Shuyuan;Cao, Jingpu;Qiao, Changcheng
甚低频（VLF）声在海底结构地球声模型的水下探测和估计中具有重要的潜力。在海洋环境中，一种VLF声音是界面波。这些波被困在流固界面附近，被称为Scholte波，这是本研究的主题。本文在南海进行了实地实验，目的是激发肖尔特波并研究其传播。这些数据是由安装在海底的海底地震仪获得的。靠近海面的大体积气枪阵列提供声源。基波和三个高阶模式的肖特波被激发。利用地震记录和相速度反演研究了肖尔特波。观测到的频率范围为1.0-2.9 Hz。在峰值频率1.4 Hz处，能量衰减与1/r成正比。通过最小二乘反演算法，从频散曲线上揭示了海底600 m以下的横波速度结构。反演结果表明，最上层的横波速度在300 m/s以下，这很好地解释了本次实验中Scholte波的弱激发。
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.