Dispersion characteristics of seabed Scholte waves with variable velocity seawater in deep water

考虑海水速度变化的深海海底Scholte波频散特性研究

Acoustic velocity varies in deep-water environments.To obtain accurate inversion interpretations,it is necessary to develop a horizontally layered seawater–seabed(HLSS)model with continuously varying velocities.In this work,we used an HLSS model based on wave theory to deduce the Scholte wave dispersion equations and established an HLSS model based on the acoustic velocity profile and the submarine medium parameters of the South China Sea.We studied the dispersion characteristics of Scholte waves and theoretically calculated the amplitude–depth distribution.We also examined the influence of deep-water environments on the dispersion characteristics of Scholte waves.Using the real geological parameters of the Dongsha Islands in the South China Sea,we exploited the spectral element method to simulate seismic wave propagation in the fluid–solid interface and extracted the Scholte wave dispersion curves using multichannel analysis of surface waves(MASW).The consistent theoretical and extracted dispersion curve results verified the accuracy of our method.Numerical experiments showed that the dispersion characteristics of Scholte waves in deep water are weaker than those in shallow water.In addition to the seawater depth and the physical parameters of seabed sediments,the seawater’s variable velocity also influences Scholte wave dispersion characteristics.

深海环境下海水的声波速度是非匀速的,为此需建立速度连续变化的水平分层海水–海底(HLSS)模型以获得精确的反演解释。首先,本文基于波动理论进行HLSS模型建模,推导Scholte波频散方程。然后,利用南海真实的海水声速剖面和海底介质参数建立HLSS模型,研究该模型Scholte波的频散特征,并对其振幅深度分布进行了理论计算,分析了深海环境对Scholte波频散特性的影响。最后,基于中国南海东沙群岛海域实际地质物性参数,利用谱元法模拟地震波在海底流–固界面的传播,并采用多道面波分析(MASW)方法提取Scholte波频散曲线,将频散曲线的理论结果与提取结果进行对比,二者结果吻合较好,验证了本文方法的准确性。实验结果表明:深海Scholte波频散特征比浅海Scholte波频散特征弱,除海水深度和海底沉积物物性参数影响外,海水速度变化对海底Scholte波频散特征也有很大的影响。