Sunday, March 26, 2023

National Tsunami Awareness Week 2023

Tsunami Risk Maps - Credit NWS NTHMP


Although we tend to think that the worst thing that could slam into our coastal communities is a CAT 5 hurricane, tsunamis (tidal waves) occur with surprising frequency around the world - and while thought of mostly as a Western Pacific threat - even the Atlantic and Gulf coasts of North America are at risk. 

Credit NOAA 2012 slide presentation       

The National Tsunami Hazard Mitigation Program (NTHMP) recognizes Tsunami Preparedness Week during the last week in March to coincide with the anniversary of the 1964 Great Alaska Earthquake and Tsunamis.

While truly massive tsunamis don't happen very often, when they do they can produce extremely high mortality, and extensive property and infrastructure damage.

The two biggest ones in recent history are the 2004 Indian Ocean Tsunami, which killed upwards to 250,000 people, and Japan's 2011 Tōhoku Earthquake & Tsunami which killed in excess of 15,000 people.
While less deadly, Alaska's 1964 earthquake produced significant tsunami effects both locally, and thousands of miles away, killing 5 in Oregon and 13 in California. Chile's 1960 Valdivia earthquake sent a train of tsunamis across the Pacific, causing heavy damage and loss of life in Hawaii, Japan, and beyond (see NOAA Report).


Tsunamis are usually generated by large earthquakes, or underwater volcanic explosions, although massive undersea avalanches - and in rare instances - an asteroid strike can generate one.  

The west coast of North America, since it is vulnerable to tsunamis generated by seismic events in Japan, Alaska, and throughout the Pacific rim - including the long expected `big one' off the Pacific Northwest's coast (see Just A Matter Of Time) - is viewed as the most `at risk' region of the continental United States and Canada.

In 2013 the USGS released a report detailing the likely West Coast impact of a tsunami generated by a 9.1 Alaskan earthquake – and the numbers are sobering.  From the USGS news release  Experts Team Up on Tsunami Resilience in California:

In this scenario approximately 750,000 people would need to be evacuated, with 90,000 of those being tourists and visitors. Additionally, one-third of the boats in California's marinas could be damaged or completely sunk, resulting in $700 million in losses. It was concluded that neither of California's nuclear power plants would likely be damaged by this particular event.

The study (link) also estimates damage to marinas, businesses and homes range between $3.5 billion and $6 billion, and as many as 8,500 could be left homeless. 

But, as we've discussed previously (see The Caribbean’s Hidden Tsunami Potential (Revisited), both the Caribbean and the Atlantic also have a history of seismic activity, making our East and Gulf Coast vulnerable to tidal waves as well. 

In 1995, Montserrat's previously dormant Soufrière Hills volcano sprang to life, destroying the capital city of Plymouth, and rendering half the island uninhabitable.

In 2013 the  USGS warned the Earthquake/Tsunami Hazard in Caribbean Higher Than Previously Thought, stating `Enough strain may be currently stored in an earthquake zone near the island of Guadeloupe to cause a magnitude 8 or larger earthquake and subsequent tsunami in the Caribbean’ 

list of known or suspected Atlantic Tsunamis includes:

  • November 1, 1755 - Lisbon, Portugal
  • October 11, 1918 - Puerto Rico
  • November 18, 1929 - Newfoundland
  • August 4, 1946 - Dominican Republic
  • August 18, 1946 - Dominican Republic
  • November 14, 1840 - Great Swell on the Delaware River
  • November 17, 1872 - Maine
  • January 9, 1926 - Maine
  • May 19, 1964 - Northeast USA

Around 11pm on July 3rd, 1992, a `rogue wave'  described by witnesses as being between 10 and 18 feet tall - slammed onto a 27 mile stretch of Florida Beaches (including Daytona Beach) and smashed hundreds of cars and caused as many as 75 (mostly minor) injuries.

Had it occurred 12 hours earlier, thousands of people would have been in the water. A reminder that the unexpected can happen, with little or no warning, at any time. 

First some preparedness advice from  After which, I'll return with a brief postscript.


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.


  • If caused by an earthquake, Drop, Cover, then Hold On to protect yourself from the earthquake first.
  • Get to high ground as far inland as possible
  • Be alert to signs of a tsunami, such as a sudden rise or draining of ocean waters.
  • Listen to emergency information and alerts. Always follow the instructions from local emergency managers.
  • Evacuate: DO NOT wait! Leave as soon as you see any natural signs of a tsunami or receive an official tsunami warning.
  • If you are in a boat, go out to sea.

Prepare NOW

  • 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.
  • Create a family emergency communication plan that has an out-of-state contact. Plan where to meet if you get separated.
  • Sign up for your community’s warning system. 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.

Survive DURING

  • If there is an earthquake and you are in a tsunami area, protect yourself from the earthquake first. Drop, 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. Evacuation routes often are marked by a wave with an arrow in the direction of higher ground.
  • If you are in the water, then grab onto something that floats, such as a raft or tree trunk.
  • 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.

Even if you don't live close enough to the coast to be directly affected by a Tsunami, a major natural disaster anywhere near you can impact your life as well.  Supply chains may be disrupted, roads, railways, and ports may be damaged, and utilities like power and water may be out for an extended period of time. 

Knowing your local threats, whether they be tsunamis, forest fires, floods, earthquakes or hurricanes  . . . and then becoming prepared to deal with them, will provide you and your family the best safety insurance available. 

For help in getting better prepared for a variety of emergencies, I would invite you to visit: 




 And some of my practical preparedness blogs from the past year you may wish to revisit include:

The Gift of Preparedness

#NatlPrep: When Evacuation Is The Better Part of Valor

Sweltering In Place (2022 Edition)

Hurricane Preparedness: Some Simple Off-The-Shelf Solar Solutions For Power Outages