I finally found the graph I have been looking for, showing tsunami heights in Japan. These data from a preliminary report comes from yet another clearinghouse type site for tsunami data and information, the Coastal Engineering Committee of the Japan Society of Civil Engineers. The geographic location of the individual data points are not indicated, other than distance from tsunami "ground zero." Regular tidal fluctuations have not been removed. There is a lot of scatter and very high values at a distance of 0 km. The highest height shown is 30 meters (100 feet!), and there are consistent heights of over 15 meters (50 feet).
Click on the image for a more readable version.