Tsunami watches and warnings are disseminated by PTWC to over 100 dissemination points scattered throughout the Pacific Basin under the varying control of the member states with general guidance from IOC, and the ICG/ITSU. These major dissemination points are responsible for further dissemination to hundreds of other points within their geographical jurisdictions.

The major dissemination responsibility of the ITWS is the tsunami watch and/or warning.

The dissemination program is a sophisticated cooperative venture using existing national and international communication facilities. The communications systems to over 100 dissemination points along with over 100 data gathering stations are tested monthly with dummy messages. The tests are monitored for minimum message travel times.

These dissemination points in turn disseminate to many more points in their respective local areas.

Citation source: http://www.drgeorgepc.com/TsunamiFAQ.html