In the United States, the National Oceanic and Atmospheric Administration, or NOAA, issues tsunami warnings. They do this through a network of various agencies, broadcasts and warning systems.
Two NOAA centers, the National Tsunami Warning Center located in Palmer, Alaska, and the Pacific Tsunami Warning Center located in Hawaii, monitor the ocean for earthquakes using earthquake information, tide guages and tsunami-detection buoys. When the NOAA issues a tsunami watch or warning, the National Weather Service activates the EAS, or Emergency Alert System, which then submits the tsunami information to local and national broadcasters. Using this information, local officials in coastal regions then decide on evacuation procedures.