It has been 10 years since the magnitude 9.1 earthquake and resulting tsunami hit Japan, on March 11, 2011 [Errata: Miyagi is misspelled. Apologies.]
Scientific lessons learned and described here include:
1. Tsunami geology can extend the earthquake record by centuries or millenia.
2. Earthquake Early Warning can mitigate damage and save lives, but the 2011earthquake revealed limitations of a system using only seismometers.
3. Adding Global Positioning System observations of earthquake ground motion improves accuracy of earthquake early warning, and is essential to tsunami warnings.

Errata: spelling of Miyagi.