f Free Surface Boundary Conditions for Elastic Staggered-Grid Modelling Schemes

The purpose of the work presented here is to describe an accurate and simple implementation of the clastic free surface for staggered grid modeling schemes. An analysis for acoustic waves demonstrates that a horizontal free surface can be implemented using two methods. One method give the free surface on the main node system in a staggered grid scheme, the other method give the free surface midway between nodes. Both methods are utilized when implementing the elastic free surface on a staggered grid. The proposed scheme show excellent agreement with a direct global matrix method.