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Hazards - Tsunami
Overview of the Hazard
Tsunamis are a series of enormous waves following seismic events, created by an underwater disturbance such as an earthquake, landslide, volcanic eruption, or meteorite. Tsunamis are threats to any coastal region, specifically Florida which has 1,197 miles of coastline, more than any of the lower 48 States. From the area where the tsunami originates, waves travel outward in all directions. Once the wave approaches the shore, it builds in height. Tsunami waves move up to 500 mph over the open ocean, then slow considerably as they approach coastal areas. On rare occasions, tsunamis can affect the Florida east coast, with wave heights above 3 feet (possibly up to 15 feet in isolated areas during the most significant events), along with very strong and dangerous currents. Wave run-up may reach up to 300 feet inland from the high tide zone during the most significant tsunami events.
Tsunami Quick Facts
What Could Cause a Florida Tsunami?
The Puerto Rico Trench
- Boundary between Caribbean, North American, and South American tectonic plates
- Since 1848 eight tsunamis have originated here, causing over 2,500 deaths
- 1918 tsunami from a magnitude 7.5 earthquake killed 116 in Puerto Rico
Cumbre Vieja Volcano in the Canary Islands
- Potential for undersea landslide creating and Atlantic Ocean-wide tsunami ( a.k.a. tele-tsunami)
Azores-Gibraltar Fracture Zone
- Potential for earthquakes, causing atlantic tele-tsunamis
- 1755 earthquake devastated Lisbon, Portugal, and generated only known Atlantic tele-tsunami
Rogue Waves - not tsunamis, but still dangerous
- Little is known about this phenomenon, but likely cause is weather-related
- 1992 rogue wave swamped 30 miles of shoreline around Daytona Beach, causing 75 injuries
- 1995 rogue wave occurred from Tampa to Naples
What's being done to detect tsunamis?
DART Buoy Deployment
- Deep ocean Assessment and Reporting of Tsunamis (DART) buoys confirm tsunami propagation
- Network of seven DART buoys in operations within western Atlantic, Caribbean, and Gulf of Mexico
Seismic Monitoring Worldwide
- NOAA's Tsunami Warning Centers continuously monitor seismic activity for potential tsunami generation
- Tsunami warnings are issued if a magnitude 7 or greater earthquake is detected on or near the coast
What's being done to increase awareness and preparedness?
National Weather Service TsunamiReady Program
- A method to improve public safety associated with tsunami emergencies through a collaborative effort between federal, state, and local emergency management agencies and the public.
- Goals of TsunamiReady (http://www.tsunamiready.noaa.gov/)
Brevard County has 72 miles of susceptible shoreline and is a host to many seasonal tourists and could have an estimated 40,000 people affected by tsunami activity. According to the National Weather Service (NWS), an estimated 12,000 residents live within the Tsunami Hazard Zone.
The maximum tsunami we could see in Brevard is 1.5 feet. The danger zone in Brevard County extends 300 feet inland. Should a tsunami affect this area, residents and tourists would evacuate the beach to beyond the 300-foot danger zone (inland of coastal roadways or west of Highway A1A) and, if evacuation of danger zone is not possible, move to the second floor (at least 15 feet high) of a well-constructed building.
While tsunamis are a known hazard risk in Brevard, no tsunami has ever occurred in the County.
What would you do?
Know the Terms:
Familiarize yourself with these terms to help identify a tsunami hazard. Full definitions can be found at ready.gov
Tsunami Watches, Warnings and Advisories:
- Tsunami Watches, Warnings and Advisories are issued by NOAA's Tsunami Warning centers
- Relayed directly to media, officials, and public via the Emergency Alert System (EAS)
- Messages alerted and broadcast on NOAA weather radios
- If you feel an earthquake or observe a sudden outgoing tide, evacuate the beach immediately.
- Talk to everyone in your household about what to do if a tsunami occurs. Create and practice an evacuation plan for your family.
- Know the height of your street above sea level and the distance of your street from the coast or other high-risk waters. Evacuation orders may be based on these numbers.
- If you are a tourist, familiarize yourself with local tsunami evacuation protocols. You may be able to safely evacuate to the third floor and higher in reinforced concrete hotel structures.
According to ready.gov, here are some actions you can take to protect yourself and your property during a tsunami:
- Follow the evacuation order issued by authorities and evacuate immediately. Take your animals with you. Evacuate the beach to beyond the 300-foot danger zone (typically inland of coastal roadways)
- If evacuation of danger zone is not possible, move to the highest floor (at least 15 feet high) of a well-constructed building
- Stay away from the beach. Never go down to the beach to watch a tsunami come in. If you can see the wave you are too close to escape it. CAUTION - If there is noticeable recession in water away from the shoreline this is nature's tsunami warning and it should be heeded. You should move away immediately.
- Save yourself - not your possessions.
- Remember to help your neighbors who may require special assistance - infants, elderly, and individuals with disabilities or access or functional needs.
According to ready.gov, here are some actions you can take to protect yourself and your property after a tsunami:
- 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.
- Avoid disaster areas. Your presence might interfere with emergency response operations and put you at further risk from the residual effects of floods.
- Stay away from debris in the water; it may pose a safety hazard to people or pets.
- Check yourself for injuries and get first aid as needed before helping injured or trapped persons.
- If someone needs to be rescued, call professionals with the right equipment to help. Many people have been killed or injured trying to rescue others.
- Help people who require special assistance—infants, elderly, those without transportation, people with disabilities or access and functional needs and large families who may need additional help in an emergency situation.
- Continue using a NOAA Weather Radio or tuning to a Coast Guard station or a local radio or television station for the latest updates.
- Stay out of any building that has water around it. Tsunami water can cause floors to crack or walls to collapse.
- Use caution when re-entering buildings or homes. Tsunami-driven floodwater may have damaged buildings where you least expect it. Carefully watch every step you take.
- To avoid injury, wear protective clothing and be cautious when cleaning up.
Brevard County Emergency Management Office
1746 Cedar Street
Rockledge, Florida 32955
Tel: (321) 637-6670
Fax: (321) 633-1738