The way I understood it is that the wave amplitude of a tsunami isn't typically huge, say only a few feet[1], however it's wavelength is. Thus while normal wave

The way I understood it is that the wave amplitude of a tsunami isn't typically huge, say only a few feet[1], however it's wavelength is. Thus while normal waves can have a much larger amplitude, they're easily filtered by a low-pass filter. edit: The atmosphere between the surface and the ionosphere forms a natural low-pass filter as well. I imagine typical ocean waves as seen by us are way too high-frequency to make it up to the ionosphere. There are other, natural disturbances in the ionosphere, such as traveling planetary waves[2], but they have a significantly longer wavelength. As such the paper[3] mentions filtering them out using a high-pass filter. In the paper they show some preliminary results trying to invert the parameters in order to estimate the height of the tsunami based on the measured ionosphere disturbance based on synthetic data, and the baseline amplitude is 10cm (4 inches), which the model comes quite close to. [1]: https://earthobservatory.nasa.gov/blogs/fromthefield/2014/04/02/tsunamis-and-the-open-ocean/ https://earthobservatory.nasa.gov/blogs/fromthefield/2014/04... [2]: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JA025720 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201... [3]: https://link.springer.com/article/10.1007/s10291-022-01365-6 https://link.springer.com/article/10.1007/s10291-022-01365-6