A tsunami is a series of enormous ocean waves caused by earthquakes, underwater landslides, volcanic eruptions or asteroids. A tsunami can kill or injure people and damage or destroy buildings and infrastructure as waves come in and go out. Tsunamis can:
- Travel 20-30 miles per hour with waves 10-100 feet high.
- Cause flooding and disrupt transportation, power, communications and the water supply.
- Happen anywhere along U.S. coasts. Coasts that border the Pacific Ocean or Caribbean have the greatest risk. New Hanover County beach towns that have south-facing beaches are have a low or very low risk for activity from seismic tsunamis along Caribbean and Puerto Rican fault lines. Even though the risk is low, New Hanover County is a Tsunami Ready community.
Yes and no. A tsunami is a seismic sea wave if it is generated by an earthquake (“seismic” means relating to an earthquake), but tsunamis can also be generated by nonseismic disturbances. Thus, “tsunami” has been internationally adopted to mean waves caused by any large and sudden displacement of the ocean.
Tsunamis are not related to tides, which result from the gravitational attraction of the Sun and Moon on Earth’s oceans. Therefore, it is incorrect to call a tsunami a tidal wave.
While distant tsunamis pose a threat to all U.S. coasts, the hazard is greatest for coastlines near subduction zones, where large earthquakes and associated landslides can produce damaging waves that threaten nearby and distant coasts, like those around the Pacific and Caribbean. The U.S. East and Gulf Coasts are not near subduction zones, and earthquakes are not as large or as frequent as in other regions. The most likely sources of tsunamis on these coasts are underwater landslides and meteotsunamis.
Tsunami messages are issued by the Tsunami Warning Centers to notify emergency managers and other local officials, the public, and other partners about the potential for a tsunami following a possible tsunami-generating event. For the United States, Canada, and the British Virgin Islands, these messages include alerts. There are four levels of tsunami alerts: warning, advisory, watch, and information statement.
- A tsunami information statement is issued when an earthquake or tsunami has occurred of interest to the message recipients. In most cases, information statements are issued to indicate there is no threat of a destructive basin-wide tsunami and to prevent unnecessary evacuations. Information statements for distant events requiring evaluation may be upgraded to a warning, advisory, or watch based on updated information and analysis.
- 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 the repositioning of ships to deep waters when there is time to safely do so. Advisories may be updated, adjusted geographically, upgraded to a warning, or canceled based on updated information and analysis.
- A tsunami watch is issued when a tsunami may later impact the watch area. The watch may be upgraded to a warning or advisory or canceled based on updated information and analysis. Emergency management officials and the public should prepare to take action.
- 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 the evacuation of low-lying coastal areas and the repositioning of ships to deep waters when there is time to safely do so. Warnings may be updated, adjusted geographically, downgraded, or canceled based on updated information and analysis.
TsunamiReady® is a voluntary community recognition program that promotes tsunami hazard preparedness as an active collaboration among federal, state/territorial and local emergency management agencies, community leaders and the public. The main goal of the program is to improve public safety before, during and after tsunami emergencies. It aims to do this by establishing guidelines for a standard level of capability to mitigate, prepare for and respond to tsunamis and working with communities to help them meet the guidelines and ultimately become recognized as TsunamiReady® by the NWS. Participating in this program can also help to provide discounts on flood insurance in our community.
In order for the National Weather Service (NWS) to recognize a community as TsunamiReady, the community must have implemented the activities established in the TsunamiReady Guidelines. These activities include:
- Defining tsunami hazard zones, producing evacuation maps and installing evacuation route signs
- Supporting ongoing, sustained tsunami public education and outreach, including to schools in tsunami hazard zones
- Establishing a 24-hour warning point and supporting emergency operations center operations
- Having more than one way to receive tsunami warnings and to alert the public
- Developing a formal tsunami operations plan and holding annual exercises
- Learn the signs of a potential tsunami, such as an earthquake, a loud roar from the ocean, or unusual ocean behavior, such as a sudden rise or wall of water or sudden draining of water showing the ocean floor.
- Know and practice community evacuation plans. Some at-risk communities have maps with evacuation zones and routes. Map out your routes from home, work and play. Pick shelters 100 feet or more above sea level, or at least one mile inland.
- Participate in the annual Great Southeast Shakeout held every October
- Create a family emergency communication plan that has an out-of-state contact. Plan where to meet if you get separated.
- Sign up to receive emergency alerts. The Emergency Alert System (EAS) and National Oceanic and Atmospheric Administration (NOAA) Weather Radio also provide emergency alerts.
- Consider earthquake insurance and a flood insurance policy through the National Flood Insurance Program (NFIP). Standard homeowner’s insurance does not cover flood or earthquake damage.
- If there is an earthquake and you are in a tsunami area, protect yourself from the earthquake first. Drop (or Lock), Cover, and Hold On. Drop to your hands and knees. Cover your head and neck with your arms. Hold on to any sturdy furniture until the shaking stops. Crawl only if you can reach a better cover, but do not go through an area with more debris.
- When the shaking stops, if there are natural signs or official warnings of a tsunami, move immediately to a safe place as high and as far inland as possible. Listen to the authorities, but do not wait for tsunami warnings and evacuation orders.
- If you are outside of the tsunami hazard zone and receive a warning, stay where you are unless officials tell you otherwise.
- Leave immediately if you are told to do so.. If you are at a lifeguarded beach, lifeguards will clear the beaches.
- If you are in the water, get out of the water if possible. Grab onto something that floats, such as a raft.
- If you are in a boat, face the direction of the waves and head out to sea. If you are in a harbor, go inland.
- Listen to local alerts and authorities for information on areas to avoid and shelter locations.
- Save phone calls for emergencies. Phone systems often are down or busy after a disaster. Use text messages or social media to communicate with family and friends.
- Avoid wading in floodwater, which can contain dangerous debris. Water may be deeper than it appears.
- Be aware of the risk of electrocution. Underground or downed power lines can electrically charge water. Do not touch electrical equipment if it is wet or if you are standing in water.
- Stay away from damaged buildings, roads and bridges.
- If you become injured or sick and need medical attention, contact your healthcare provider and shelter in place, if possible. Call 9-1-1 if you are experiencing a medical emergency.
- Document property damage with photographs. Conduct an inventory and contact your insurance company for assistance.