基于等效密度流体近似反射模型反演海底参数

Bottom parameters inversion based on reflection model of effective density fluid approximation

为了获取海底沉积物的物理和地声特性,根据等效密度流体近似反射模型得到的不同掠射角下的海底反射损失,利用差分进化算法和粒子群算法相结合的两级混合优化算法以及Bayesian反演方法对海底沉积物的孔隙度、平均颗粒粒度、颗粒质量密度以及颗粒体积弹性模量进行反演,再根据这4个物理参数的估计值进一步计算出海底地声参数,包括声速和衰减。通过反演结果与仿真真值的比较可以看出,除颗粒体积弹性模量外,得到的估计结果是令人满意的,特别是这种间接反演海底地声参数的方法对地声参数的估计具有较高的精确性和较强的稳健性,相对误差分别为0.092%和17%。最后,对实验室水池池底沙质沉积物的反射损失数据进行处理,给出了沙质沉积物各参数的估计值、不确定性和相关性,并通过反演结果与部分实测参数值的比较验证了反演方法的可行性。

In order to obtain the physical and geoacoustic properties of marine sediments, an inverse method using reflection loss of different grazing angles is presented. The reflection loss is calculated according to the reflection model of effective density fluid approximation. A two-step hybrid optimization algorithm combining differential evolution and particle swarm optimization along with Bayesian inversion are employed in estimation of porosity, mean grain size, mass density and bulk modulus of grains, respectively. Based on above physical parameters, geoacoustic parameters, including sound speed and attenuation, are further calculated. Numerical simulations show that all the parameters can be well estimated with the exception of bulk modulus of grains. In particular, this indirect inverse method for bottom geoacoustic parameters performs high accuracy and strong robustness. The relative errors are 0.092% and 17%, respectively. Finally, measured reflection loss data of sandy sediments at the bottom of a water tank is analyzed, and the estimation value, uncertainty and correlation of each parameter are presented. And the availability of this inverse method is verified through comparison between inverse results and part of measured parameters