# Background of PML

PML was originally developed for electromagnetic waves in seminal works by Bérenger and Chew in 1994, and followed up by extensive investigation of electromagnetic PMLs by numerous researchers, as well as extensions to other fields such as elastic waves for seismic applications.

Most of these formulations and implementations used finite-difference split-field methods to implement the PML, which had two disadvantages: (i) the finite-difference methods could not be used easily with finite-element models for structures, and (ii) the split-field formulation often led to long-time instability.

These shortcomings were rectified for elastic PMLs by Basu and Chopra [2003, 2004, 2009] by developing a displacement-based finite-element implementation that allowed explicit analysis, thus enabling realistic analysis of three-dimensional soil-structure systems.