evacuations. In addition to its basic functions, the Center conducts a community preparedness program intended to increase public awareness of the tsunami hazard and improve tsunami planning at the community level. The Center also actively pursues developmental projects which enhance tsunami warning operations. The Center operates 24 hours every day with two watchstanders on duty. Center personnel are notified of activity by an alarm system which is activated by several methods: Sustained, strong oscillatory motion at individual seismometers. Activation by multiple earthquake arrivals observed in sectors of the globe within a specified time interval. Activation by a real-time seismic processing system when an earthquake exceeds a predetermined magnitude threshold for various regions throughout the world. Deep ocean tsunami sensor detection of an event. Bulletins Depending on the seismic data (Message Definitions), NTWC will issue the following types of bulletins: Warning A tsunami warning is issued when a tsunami with the potential to generate widespread inundation is imminent, expected, or occurring. Warnings alert the public that dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after initial arrival. Warnings alert emergency management officials to take action for the entire tsunami hazard zone. Appropriate actions to be taken by local officials may include evacuating low-lying coastal areas, and moving ships to deep water when there is time to safely do so. Warnings may be updated, adjusted geographically, downgraded, or canceled. To provide the earliest possible alert, initial warnings are normally based only on seismic information. Advisory A tsunami advisory is issued when a tsunami with the potential to generate strong currents or waves dangerous to those in or very near the water is imminent, expected, or occurring. The threat may continue for several hours after initial arrival, but significant inundation is not expected for areas under an advisory. Appropriate actions to be taken by local officials may include closing beaches, evacuating harbors and marinas, and moving ships to deep water when there is time to safely do so. Advisories are normally updated to continue the advisory, expand/contract affected areas, upgrade to a warning, or cancel the advisory. Watch A tsunami watch is issued to alert emergency management officials and the public of an event which may later impact the watch area. The watch may be upgraded to a warning or advisory – or canceled – based on updated information and analysis. Therefore, emergency management officials and