Application of nearly perfectly matched layer technique in poroviscoelastic wave modelling based on effective biot theory

The upscaled poro-viscoelastic equations of effective Biot theory and their corresponding nearly-perfectly matched layer (NPML) boundary conditions are discretised with a 9-point mixed-staggered grid stencil finite-difference method. The damping factor function in the NPML condition should be adjusted if the source centre frequency changes significantly. Otherwise, the NPML zone could lose its effectiveness. This is of critical importance since we aim to conduct seismic wave simulations across a very broad frequency range based on effective Biot theory. Two methods are suggested to adjust the damping factor function in the NPML boundary condition to ensure its effectiveness for broad band modelling.