A promising tsunami warning system outlined here links Total Electron Content (TEC) disturbances in the ionosphere detected by GNSS satellites to maps of inundated areas along the affected coastlines. This will be accomplished through a pipeline of earthquake, ionosphere, and tsunami simulations. The focus of this paper is to demonstrate the feasibility and validity of our tsunami simulator for use in this simulation pipeline. The simulator we have developed is called Tsunami Squares, a computationally inexpensive program that employs a unique method of propagating water according to shallow water theory. Unlike other wave simulators, Tsunami Squares can easily propagate waves from sea to land, allowing flooded areas along the coast to be mapped. To validate its accuracy, a comparison is made to the Regional Ocean Modeling System tsunami simulator, which solves the Navier Stokes equations directly using a finitedifference method. The two simulation techniques show good agreement when compared over the 2011 Japan event and the 2010 Chile event. In addition, examples of inundation plots are displayed here to demonstrate its capability for such a warning system.