The slip patch (where the two tectonic plates slip past each other) of the earthquake did not reach the sea floor, so it didn't generate a big tsunami [0]. If

The slip patch (where the two tectonic plates slip past each other) of the earthquake did not reach the sea floor, so it didn't generate a big tsunami [0]. If the purple colors in the finite fault map (indicating >2 m slip) reached the trench (the top of the first figure, or the red line in the second), then the earthquake would have displaced much more seawater. These finite fault maps are made using automated processing of the seismic waves from seismographs around the globe. It's pretty amazing to me that the resolution is so good, from what are not that different than sound waves. These tend to be pretty accurate, not just precise, and are validated from additional studies using different datasets over the subsequent years. [0]: https://earthquake.usgs.gov/earthquakes/eventpage/us6000f02w/finite-fault https://earthquake.usgs.gov/earthquakes/eventpage/us6000f02w...