If you’ve seen and heard about the tsunami that hit Sumatra in 2004, you may be wondering how you to could survive a tsunami in the worst case scenario.
Tsunami’s are not to be taken likely, take for example the tsunami that hit Japan in 2011. The wave, 32 feet (10 meters) high and travelling at 497 mph (800 kph) (in the deep ocean) swept over the east coast of Japan killing more than 18 000 people!
Knowing how to survive a tsunami is paramount, especially if you live in the known fault zone areas.
Understanding the Tsunami Hazard
Profile of a Tsunami
Tsunamis are the result of sudden, large-scale water displacement.
They have many causes, such as landslides under or into water, massive submarine earthquakes, eruptions of coastal or island volcanoes and even by meteor impacts in water.
For most of the coastlines along the Pacific Northwest the most common reasons for tsunamis are earthquakes and landslides.
It’s tsunamis from earthquakes that pose the greatest threat to life on land.
The biggest most ferocious tsunamis are produced by earthquakes that rupture along subduction zones. This is where geologic forces drive oceanic tectonic plates beneath a continental plate.
Sudden large movements along these zones produce massive earthquakes reaching a magnitude of 8.0 and higher, with terrifying ground shaking that can last several minutes.
The immediate movement of the seafloor as it lifts and drops when the fault zone breaks, pushes the water above the rupture, it’s this displacement of water that creates a tsunami.
Tsunami Speeds and Shapes
Most of the waves you and I experience daily are wind driven waves that travel through the surface layers of the ocean. Tsunamis however, travel through the entire column of water, right from the seafloor to the surface.
Tsunami waves speed depends on the depth of the water in the open ocean. They travel at high speeds often reaching nearly 500 miles (800km) per hour. As the wave reaches shallower water, they slow down to around 20 – 30 miles (32 – 48 km) per hour. This is when the waves increase in height.
The visual appearance and behavior of a tsunami wave as it approaches largely depends on the underwater topography of the shoreline.
Generally though, tsunami waves look less like a cresting ocean wave surfers so belove and more like a surging wall of water.
A tsunami does not consist of merely one wave but rather of a series of waves, that reach the shoreline at intervals over many hours. Often the first waves are not the largest of the series.
Tsunami’s effects include:
- Rapid flooding of low-lying land
- Dangerously strong ocean currents
As the wall of water travels inland, it picks up large debris, which gives the wave even more destructive force.
Tsunami Risk Areas
According to NOAA Center for Tsunami Research. Tsunami’s often take place in the pacific ocean. The pacific rim which surrounds the ocean, has a large number of active submarine earthquake zones.
Countries immediately affected are:
- West Coast USA
- New Zealand
How to Survive a Tsunami
Step 1 – Be Aware and Prepare
If you live within 10 miles (16km) of the coastline, particularly in one of the tsunami risk areas mentioned above, be aware of any earth tremors (earthquakes).
Some communities living in tsunami risk areas have maps with evacuation zones and routes, make yourself familiar with these routes. Check out this example of a tsunami evacuation drill.
Inform yourself and your family, practice community evacuation plans and map out your routes from home to be prepared in any event. Preparedness can mean the difference between life or death.
Ensure that your family has the essential emergency supplies. I recommend checking out this emergency family preparedness kit for a family of four.
The kit will keep you and your family going for 72 hours until help arrives.
Step 2 – Know The Signs
Learn the early warning signs of an impending tsunami. One of the main signs of a tsunami is if you experience a strong earthquake that lasts for more than 20 seconds.
A more immediate and ominous sign that a tsunami may be approaching, is if there is a fast unexpected recession of water levels below the expected low tide mark.
Witnessing this however means there could be minutes before the shoreline is struck by a tsunami. It is however the only immediate warning sign for areas located too far from the earthquake epicentre to have felt the shaking.
An approaching tsunami will often create a roaring sound similar to that of a train or jet aircraft.
Step 3 – Get to Higher Ground
Once you’ve been alerted to the signs of an approaching tsunami, the best thing to do is get to higher ground as quickly and efficiently as possible (even if you have not yet been alerted by an official warning). This is where your tsunami evacuation drill comes in handy.
If higher ground is near, it’s recommended to evacuate on foot, doing this will avoid gridlock caused by too many cars.
Head for any sort of higher ground, ideally 100 feet (30 meters) or higher. As you head for high ground, make sure to stay away from rivers and streams. Tsunami’s can move up river incredibly fast, many people have been caught by surprise by this.
If you can’t get to higher ground quickly, get in your car and drive away from the coast. From 5 miles 8 (km) onwards you should be safe, but to be extra sure, travel as far as 10 miles (16km) plus.
What if you can’t escape in time?
The general rule of thumb is if you can see a tsunami wave it’s unlikely you’ll be able to outrun it. If this is the case you should look for any immediate signs of shelter.
Try to find a sturdy, reinforced concrete building. Climb as high as you can—ideally to the third floor— head for the roof.
If there are no buildings, climb to the top of the sturdiest looking tree.
If all else fails, hang onto some floating debris, go with the flow. Survival at this stage is simply a matter of luck.
Step 4 – Stay on High Ground
If you’ve managed to escape to higher ground, STAY THERE.
Many people have perished by assuming that the first wave was the entire extent to the disaster. Remember there will always be follow-up waves (in the same way that when you throw a pebble into a puddle there’s a series of ripples).
Make sure to wait on higher ground until you get the clear from emergency personnel, this could take anywhere between 2 – 5 hours.
It’s possible that cell phone service could fail during the disaster, that’s why I always recommend packing the lightweight Kaito KA500 solar powered radio into your preparedness bag.
Ten Tsunami facts
- 1720 feet (524 meters) was the size of the biggest tsunami wave ever recorded. It hit Lituya Bay, Alaska in July 1958.
- Around 80% of tsunamis happen within the Pacific Ocean’s “ring of fire”.
- The first wave of a tsunami is usually not the strongest, the series of waves following get bigger and stronger each time.
- Tsunami’s can reach speeds of up to 500 miles (805 km) per hour in the deep ocean. That’s as fast as a jet plane.
- The states in the U.S at greatest risk for tsunamis are Hawaii, Alaska, Washington, Oregon and California.
- If caught inside a tsunami wave it is better not to swim but rather hold onto a floating piece of debris.
- Tsunamis retain their energy which means they can travel across entire oceans within hours with limited energy loss.
- Tsunami is Japanese which translates to harbor wave, (tsu = harbor + nami = wave).
- Scientists are able to accurately determine the time at which a tsunami will make landfall almost anywhere in the world. They use calculations based on the depth of water, distances from place to place and the time at which the earthquake occurred.
- Hawaii gets about one tsunami every year and a severe one every 7 years.
- In 2004, a total of 283,000 people was killed around the world by killer waves radiating out from the epicenter of a massive earthquake (equivalent of 23,000 atomic bombs) in the Indian Ocean.