Hybrid Asynchronous Perfectly Matched Layer for seismic wave propagation in unbounded domains

Perfectly Matched Layer (PML) is recognized as a very effective tool for modeling unbounded domains. Nonetheless, the computation time required by the PML may be large, especially when an explicit time integration scheme is adopted for dealing with the wave propagation problem both in the domain of interest and in the PML medium. In this paper, it is proposed to investigate subdomain strategies enabling the appropriate time integration scheme in the PML with its own time step to be chosen, independently of the choice of the time scheme in the domain of interest. We focus on explicit time integrator in the physical subdomain (Central Difference scheme) associated with a fine time step satisfying the CFL stability criterion. The PML formulation proposed by Basu and Chopra (2004) [1] for 2D transient dynamics, has been coupled with the interior physical subdomain using the dual Schur approach proposed by Gravouil and Combescure (2001) [2]. Hybrid (implicit time integrator for the PML) asynchronous (multi time steps) PMLs have been derived. Their very good accuracy has been shown by considering the following numerical examples: Lamb׳s test, loaded rigid strip footing on an half space and a layered half space.