A Tsunami Warning Indicates that a tsunami is imminent and that coastal locations in the warned area should prepare for flooding. The initial warning is typically based on seismic information alone. Earthquakes over magnitude 7.0 triggers a warning covering the coastal regions within 2 hours tsunami travel time from the epicenter. When the magnitude is over 7.5, the warned area is increased to 3 hours tsunami travel time. As water level data showing the tsunami is recorded, the warning will be cancelled, restricted, expanded incrementally, or expanded in the event of a major tsunami.
What to Do When a Tsunami Warning Is Issued
- Use a NOAA Weather Radio or stay tuned to a Coast Guard emergency frequency station, or a local radio or television station for updated emergency information.
- Follow instructions issued by local authorities. Recommended evacuation routes may be different from the one you planned, or you may be advised to climb higher. Remember, authorities will issue a warning only if they believe there is a real threat from tsunami.
- If you hear an official tsunami warning or detect signs of a tsunami, evacuate at once. A tsunami warning is issued when authorities are certain that a tsunami threat exists, and there may be little time to get out.
- Take your Disaster Supplies Kit. Having supplies will make you more comfortable during the evacuation.
- Get to higher ground as far inland as possible. Officials cannot reliably predict either the height or local effects of tsunamis.
- Watching a tsunami from the beach or cliffs could put you in grave danger. If you can see the wave, you are too close to escape it.
- Return home only after local officials tell you it is safe. A tsunami is a series of waves that may continue for hours. Do not assume that after one wave the danger is over. The next wave may be larger than the first one. In several cases, people survived the first wave and returned to homes and businesses only to be trapped and killed by later, sometimes larger, waves in the series.
- If you evacuate, take your animals with you. If it is not safe for you, it is not safe for your animals.
- If you cannot escape a wave, climb onto a roof or up a tree, or grab a floating object and hang on until help arrives. Some people have survived tsunami waves by using these last-resort methods.
FOR HAWAII, IF EVACUATION IS NECESSARY SIRENS WILL BE ACTIVATED
FOR CURRENT INFORMATION Listen to local radio, television broadcasts, internet media
Local sources for information in Hawai’i include:
NOAA Weather Radio Broadcasts on following frequencies:
NOAA Weather Radio Broadcasts recording phone numbers:
Maui: (808) 871-6706
Lanai: (808) 565-6033
Molokai: (808) 552-2477
Tsunami Information Links
Tsunami Evacuation Maps for the Big Island
Tsunami Evacuation Zones
Pacific Tsunami Warning Center
West Coast and Alaska Tsunami Info
International Tsunami Information Center
Pacific Disaster Center
Recent and Historical Tsunami Events
USGS: How large does an earthquake have to be to cause a tsunami?
Magnitudes below 6.5
Earthquakes of this magnitude are very unlikely to trigger a tsunami.
Magnitudes between 6.5 and 7.5
Earthquakes of this size do not usually produce destructive tsunamis. However, small sea level changes may be observed in the vicinity of the epicenter. Tsunamis capable of producing damage or casualties are rare in this magnitude range but have occurred due to secondary effects such as landslides or submarine slumps.
Magnitudes between 7.6 and 7.8
Earthquakes of this size may produce destructive tsunamis especially near the epicenter; at greater distances small sea level changes may be observed. Tsunamis capable of producing damage at great distances are rare in the magnitude range.
Magnitude 7.9 and greater
Destructive local tsunamis are possible near the epicenter, and significant sea level changes and damage may occur in a broader region.
Note that with a magnitude 9.0 earthquake, the probability of an aftershock with a magnitude exceeding 7.5 is not negligible. To date, the largest aftershock recorded has been magnitude 7.1 that did not produce a damaging tsunami.
A Decade of Great Earthquakes