Thursday, November 03, 2022

World Tsunami Awareness Day, November 5, 2022

Tsunami warnings like this are or should be becoming much more common
 

As it happens, the 5th of November is World Tsunami Awareness Day.  Although Tsunamis are among the rarest of natural phenomena, they are also among the most deadly and destructive. While far more frequent in the Pacific they can also happen in other places such as Europe and the eastern seaboard of the USA. An analysis of 290 events between 1992 and 2016 showed that while 77% of them occurred around the margins of the Pacific Ocean, 9% occurred in both the Indian and Atlantic Oceans and 5% along the Mediterranean.


Earthquakes from 1992 to 2016


Nor do you have to live on the coast to experience a tsunami. They can also occur in inland waterways and lakes. In 1963, around 2000 people were killed and several towns including Longarone in Northern Italy were completely obliterated by a tsunami which followed a landslide  on an upstream dam.

Norway has had no less than 10 tsunamis since 1888, the largest of which occurred in 1998. These are usually the result of earth movements, particularly rockfalls above fjords, but generally there is little loss of life due to excellent seismic and geological monitoring which followed one of the most deadly tsunamis in 1936. 

Why we have a World Tsunami Day

The aims of World Tsunami Awareness Day are to alert people to the risk and to make vulnerable communities safer. Here's what the UN says,

"A common theme that has emerged time and again is the importance of education, including evacuation drills, for ensuring that communities act decisively and without panic when the tsunami warnings reach them. For local tsunamis, it is even more important that every person knows the tsunami's natural warning signs and immediately self-evacuates since the waves could attack in minutes.” 

 

 

 If you live in an affected region, UNESCO’s Tsunami Ready Programme has excellent step by step guides to help prevent loss of life and property. Its three key points are:

  1. Risk Reduction 
  2. Better Preparedness
  3. Building Back Better in recovery, rehabilitation and construction. 
For more detail, see the broader UN Sendai Disaster Risk Reduction Framework here
 

Reducing the Risk

 A major factor in risk reduction has been the establishment of worldwide early warning systems. Below is a video about how they work. For more information and in other languages such as French and Spanish, click here

 

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Establishment of evacuation centres

I noticed while looking for a map that many places from New South Wales in Australia to Portland, Oregon in the USA and especially in New Zealand, have already established tsunami evacuation zones. This is just as well as we had our first official alert only last year, though the impact was less than anticipated. With almost the entire coastline of the Americas at risk here's a long list for the US and its territories.

How Tsunamis happen

Tsunamis are usually triggered by underwater earthquakes or earth movements with the energy created forcing the water outwards and upwards. As the wave reaches shallower water around shorelines it is forced to rise higher. The first wave of a tsunami is not necessarily the largest and may be followed by many more. The resulting flooding and strong waves and currents can last for many hours. The force of a tsunami may mean that large rocks, boats, even houses are carried far inland causing much damage and injury. Click here to find out more.  


This video shows how waves are pushed up in shallower waters around coastlines

 - by RĂ©gis Lachaume, CC BY-SA 3.0, via Wikimedia Commons

Natural warning signs of a Tsunami

By the time you hear a warning signal or see a giant wave, it may be too late seek higher ground, so let’s take a brief look at how to recognise other signs and what you should do. Countries which are subject to frequent tsunamis usually know what to do, so this is more or less for the rest of us who may be far from home. While the dramatic retreat of water from the beach is one of the most obvious signs, there are also more subtle ones, such as falling water levels in wells. You might also feel the shudder of an earthquake or hear a loud roaring noise. Read more here

In all cases don’t wait for confirmation but run and go as high as you can. Upper floors in tall, sturdy sturdy buildings may work if there isn't time to go anywhere else. If nothing serious happens, consider that at least you know the drill and won’t be caught flatfooted if it does. If you are a visitor, do as the locals do. Don’t try to take anything with you. Belongings can be replaced. Human lives can't.


 

 I was planning to write about other less well known natural disasters, but in the light of two recent tragedies perhaps we should talk about Crowd Surges next.


 

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