An 8.2-magnitude earthquake hit Chile on April 1, creating a tsunami that started to cross the Pacific Ocean immediately after. Although the tsunami was not really noticeable in Hawaii, where it was 20 cm tall when it hit over 12 hours after, scientists were happy that tsunami projections were available just half an hour after the earthquake hit, and accurately forecasted the tsunami height in Hawaii using computer models.
The huge Indonesian tsunami in 2004 spurred countries around the Pacific Ocean to upgrade their tsunami sensors and warning systems - there are ten times more sensors now than there were over ten years ago. They measure wave height, and are attached to buoys over deep water.
http://www.nbcnews.com/storyline/chile-earthquake/tsunami-monitoring-technology-hits-mark-chile-n70041
The huge Indonesian tsunami in 2004 spurred countries around the Pacific Ocean to upgrade their tsunami sensors and warning systems - there are ten times more sensors now than there were over ten years ago. They measure wave height, and are attached to buoys over deep water.
http://www.nbcnews.com/storyline/chile-earthquake/tsunami-monitoring-technology-hits-mark-chile-n70041
Image credit: PMEL/NOAA. Red shows the highest predicted tsunami height.