Perfectly matched layers for modelling seismic oceanography experiments

Seismic oceanography techniques are able to provide oceanographic properties of the water masses by processing seismic reflection data. These techniques have reported reflected waves due to the fine structure in the ocean, whose order of magnitude is as weak as −80 dB. Thus, if we focus our attention on numerical simulation of this kind of oceanography experiments, the numerical performance of the method should allow obtaining accurate results, where the spurious reflections from the artificial boundaries of the computational grid are, at least, one order of magnitude smaller than the physical phenomena. This can be achieved by introducing perfectly matched layers (PML), which simulate non-reflecting boundaries. The aim of this work is to propose a numerical underwater propagation method, which combines a second-order finite-difference scheme in the physical region of interest with a first-order pressure/velocity discretization in the PML domain. This numerical method provides a low-cost computational algorithm with an accuracy, which allows recovering the reflected phenomena from the ocean fine structure, and moreover, with a spurious error of order −100 dB from the PML domain.