How are watches and warnings disseminated?
When sufficient data has been received so that the earthquake can be located and the magnitude computed, a decision is made as to further action. If the earthquake is strong enough to cause a tsunami and is located in an area where this is possible, participating tide stations near the epicenter are requested to monitor their tide gauges. Watch bulletins are issued to the dissemination agencies for all earthquakes of magnitude 7 or greater occurring in the Aleutian Islands and all earthquakes of magnitude 7.5 or greater occurring elsewhere in the Pacific. A watch may also be disseminated by PTWC upon the issuance of warnings by the regional warning centers. Since the regional systems use different criteria for their disseminations, a watch may at times be issued for earthquakes with magnitude less than 7.5. When reports from tide stations show that a tsunami poses a threat to the population in a part or all of the Pacific, a warning is transmitted to the dissemination agencies for rela
