The destructive power of tsunamis is enormous. The 2004 tsunami in the in the Indian Ocean was among the deadliest natural disasters on record, killing over 230,000 people in 14 countries. Are you at risk of, and prepared for a tsunami?
More than a large wave…
Tsunamis don’t resemble normal, breaking sea waves, but a rising tide or large wall of water. Tsunamis are generally part of a series of waves, arriving in a “wave train,” ranging from 10 minutes to 2 hours to even days apart. Sixty to 300 miles wide, the waves can travel at speeds of 500-600 mph and reach heights of 32 feet or more. A sobering concept when you consider a mere two inches of water can knock you over and two feet of water can carry away most cars.
What can cause a tsunami?
- Undersea volcanic eruptions
- Underwater landslides
- Calving icebergs/glaciers
- Underwater explosions
- Meteorite impacts
- Other disturbances in the surface of the ocean
How common are tsunamis? Is my area at risk?
Historically, major tsunamis happen once per decade, however the incidence of tsunamis varies widely by coastline.
- Pacific Ocean – 59%
Most tsunamis occur in the Pacific because the ocean basin is rimmed by the Ring of Fire, a long chain of the Earth's most seismically active spots. The Pacific coastline from northern California to British Columbia is at risk from both offshore earthquakes originating from the Cascadian subduction zone, as well as distant earthquakes from across the Pacific. If a tsunami arose resulting from a Cascadian zone quakes, it could arrive on shore in as little as 12-20 minutes.
- Mediterranean Sea – 25%
Disastrous tsunamis take place in the Mediterranean on average once every century due to earthquakes caused by the shifting of the African and Eurasian plates.
- Atlantic Ocean – 12%
Scientists still don't have a good picture of exactly how plates and fault lines are structured beneath the East Coast, however no major faults or plates exist there, making chances of tsunami there low, but not impossible.
- Indian Ocean – 4%
Though tsunamis are less common in the Indian Ocean compared to other seas, this 4% incidence in light of the events of the deadly 2004 tsunami serve as a sobering reminder that statistics aren’t everything - and it is better to be prepared than caught off-guard.
Warning signs of a tsunami:
Though tsunamis cannot be predicted, forecasting possible tsunami hazards is possible with the help of seismic and sea level data, as well as computer modeling following seismic activity. Natural warning signs of a tsunami include:
- Shaking of the ground preceding the tsunami’s arrival, which may be due to the tsunami itself, or an earthquake.
- A loud roaring sound, similar to a train or jet.
- A sudden rise or fall in sea level as the tsunami approaches the shore. Receding water may expose the ocean floor, reefs, and fish.
How can I prepare for a tsunami emergency?
- Be prepared, not worried. Learn about tsunami evacuation routes and shelters before you visit at-risk areas, such as the beach.
- Take heed of the natural warning signs listed above, and act accordingly.
- Observe official warnings. Remember there will be multiple waves, minutes to days apart, so playing it safe is advisable.
- Don’t rely on roads for evacuation. Earthquakes may render them inaccessible. Be prepared to flee on foot and take shelter if necessary.
What to do in the event of a tsunami:
- In the event of a warning, avoid at-risk or low-lying areas.
- If you don’t get a warning, once shaking stops, do not wait for a for instruction to flee. Move to higher ground immediately. Save yourself, not your belongings. Though distant tsunamis generally allow people enough time to evacuate to higher ground, you may have only minutes before the tsunami strikes.
- If you do not have time to evacuate, seek out shelter in the upper floors of high, multi-story, reinforced concrete buildings, such as hotels.
- If you have no other options, climb a tall, sturdy tree.
- If you get caught in tsunami waters, find something to use as a raft to prevent fatigue, blows from debris, and drowning.
- Do not return to the affected area, or low-lying areas, until the “all clear” has been given. Danger can last for hours to days following the initial wave in the wave train.