Tsunami Travel Time MapsNGDC, as the World Data Service for Geophysics (including Tsunamis), and the UNESCOIOC International Tsunami Information Center, collaborate to provide tsunami travel time maps.
Tsunami Source Maps
Coastal Locations Maps Maps were generated using Tsunami Travel Times (TTT) software (see below) developed by Paul Wessel, Geoware. TTT software calculates firstarrival travel times on a grid for a tsunami generated at a given earthquake epicenter or coastal location.
Tsunami Travel Time SoftwareThe technique to compute travel times is an application of Huygen's principle. It states that all points on a wavefront are point sources for secondary spherical waves. Minimum travel times are computed over the grid starting at the point of interest (e.g. earthquake epicenter). From the starting point, times are computed to all surrounding points. The grid point with minimum time is then taken as the next starting point and times are computed from there to all surrounding points. The starting point is continually moved to the point with minimum total travel time until all grid points have been evaluated. This technique is explained in Shokin, et al., 1987, Calculations of tsunami travel time charts in the Pacific Ocean, Science of Tsunami Hazards, vol. 5, p. 85113. Tsunamis are categorized as long waves, therefore, tsunami travel times can be computed with water depth as the only variable (Murty, T.S., Seismic Sea Waves Tsunamis, Bulletin 198) Long waves are where the distance between wave crests is much greater than the water depth through which the wave is traveling. Wave speed is computed from the square root of the quantity: water depth times the acceleration of gravity. So, tsunami travel times can be computed without any knowledge of the tsunami's height, wavelength, etc. 
