As a lifelong resident of the Gulf Coast, I’ll be the first to say, I don’t know much about earthquakes. As a consequence, you’ll find my name absent from this whole section. Still, I have to edit, and a good editor has to ask questions, and if need be, check facts. When I noticed we had a Tsunami section, I scratched my head. I think it’s fair to ask, “Are tsunamis really a credible threat to the United States?”
First let me say, that I have no doubt places like Hawaii and US possessions in the Pacific are vulnerable, and no offense to those you there, but that doesn’t mean much to East, West, and Gulf coast residents.
As it turns out, I was…wrong.
2004 Indian Ocean Tsunami
On December 26, 2004, an earthquake off the coast of Sumatra, Indonesia created a Tsunami responsible for the loss of nearly a quarter of a million people. The quake was measured at a magnitude between 9.1 and 9.3 (the second largest ever recorded) and set off smaller quakes as far away as Alaska. The earthquake itself was felt as far away as Oklahoma.
The total energy released on the earth’s surface was estimated at 1.1×1017 joules or 26.3 megatons worth of TNT, or if I can put this crudely, more than 1502 times that of the bomb dropped on Hiroshima.
Bare in mind, we are only talking about the earthquake, not the energy from the waves themselves, which were far greater. The waves moved from 300 to 600 mph, and while that barely registered on the surface of the water as little more than a small bump (and did not threaten deep sea shipping in any way) the waves themselves swept as high as 100 feet and a mile and quarter inland. Then they traveled out again, at 300 mph or more, and back, often bigger than before. Sometimes again, and yet again.
According to Dr. Tad S. Murty, professor of Civil Engineering and Earth Sciences at the University of Ottawa, the total energy of the waves themselves were 5 megatons of TNT (20 petajoules). That is more than twice the entire explosive output of the Second World War, including the two atomic bombs.
Sixteen hours after the quake, two unfortunate souls knee deep in water in faraway South Africa, suddenly found themselves in deep water and swept out again, never to be seen again. Hollywood couldn’t write a disaster movie more horrific.
Now, I know I’m late to the game asking, “can it happen here.” Scientists all over the word asked the same thing, and shortly after the incident, under UN supervision, upgraded the tsunami warning system all over the Pacific.
The conclusion was, that not only was the west coast vulnerable to a similar sized tsunami, the possibility exists that it could face one that is even more catastrophic. In fact, the most vulnerable area on earth to a repeat performance is, wait for it, the Pacific Northwest.
A Blast From the Past
In 1964, a 9.2 Earthquake off the coast of Alaska sent a tsunami hurtling down the western coast of North America. While the quake “only” killed 131 people, property damage was felt all the way from nearby Anchorage, surrounding Alaskan villages, and the British Columbia coast (where means homes were simply washed away), all the way down to Los Angeles, where several boats were damaged. Property damage was seen even in Hawaii and Japan.
The most unfortunate however, was the small community of Crescent City, California, which insurance adjustors estimate saw more damage than even Anchorage. The waves took three hours to reach the sleepy California town and four more arrived a few hours later. In the end 12 people were dead, 100 injured and scores missing. The waves crashed on 60 city blocks, destroying 30 outright, and were responsible for 289 buildings, 1000 cars, and 25 fishing vessels.
As recently as November 15, 2006, the city saw a tsunami warning after magnitude 8.3 hit the faraway Kurile Islands (Japanese or Russian depending on whom you ask). The warning was rescinded, but shortly after a wave hit the city. While no casualties were reported, the damaged forced Governor Arnold Schwarzenegger to declare a state of emergency for the entire county.
West Coast Worries
According to Alex Molina, our resident expert on earthquakes, tsunamis are not caused by earthquakes themselves, but rather, earthquakes near subduction zones cause them. Subduction zones are places where tectonic plates rub under or above another (as opposed to side to side).
In the Pacific, and especially the Pacific Northwest, there are many subduction zones near both each other, and the coastline. What’s more, these subduction zones are in shallow water, relatively speaking. Shallower water means slower tsunamis, but much larger wave height, which means much more potential for destruction.
The most troubling of all of these, is the Cascadia Subduction Zone. Cascadia is a mere 50 miles from the Oregon coast, and stretches from the British Columbia Coast, all the way to Northern Canada. In theory, a large earthquake near Cascadia could mean a tsunami could wipe out the Oregon coast in less than 15 minutes.
The last “major” tsunami in the region, say experts, was in 1700. Researchers have found evidence of tsunamis in tree rings far inland in Northern California, from approximately 300 years ago. Researchers in Japan have found mention in several surviving records from the era and they even specify an exact date: January 26, 1700.
Most experts agree that the long look at seismic activity in the region points to another event on this scale happening soon (give or take a hundred years).
The Good News
The good news is, both sides of the Pacific are well aware of the risks and have done much to address the potential danger, even before the 2004 Tsunami brought the term back into common currency.
The Pacific Ocean is much better equipped than the Indian Ocean to give an early warning should a an underwater earthquake, no small thanks to the work of the Japanese and U.S. governments. The early-warning tidal buoys have also all been upgraded since the scare in 2004.
Communities especially vulnerable, such as the coastline of Oregon have “tsunami drills” for schoolchildren and community sirens and emergency blue sirens have been installed in many areas to alert locals to the incoming waves.
In addition, building codes have been upgraded in the Pacific Northwest, both in the U.S. and Canada to accommodate the threat of earthquakes. While it’s questionable how much this can help a structure withstand a 100-foot wave, however is something no one would like to test.
While some scientists claim that certain areas of the West Coast have no more than 15 minutes to escape a tsunami coming from the Cascadia Subduction Zone, a person who is at least aware of the threat and prepared, has enough time to rush inland to the hills and escape to safety, a few miles inland.
Conclusion
Without a doubt, the west coast of the United States and Canada, and the Pacific Northwest in particular, is one of the most likliest regions on earth to see a future catastrophic tsunami. While the likelihood is rare, the precedent exists, and those living in these coastal areas should take the threat of a tsunami very seriously.
However, it would be very careless of me to needlessly panic anyone. It’s important to add that the west coast of the United States is not India or Indonesia or Thailand. It is geographically different, and it is not nearly as densely populated. Our early-warning detection and notification system is far more advanced, and our mobility is far superior. So yes, a tsunami as powerful or even greater could hit the west coast, but the likelihood for the same scale of catastrophe, especially measured in lives lost, is extremely unlikely.
The risk in for a tsunami on the Gulf and Atlantic coasts is much smaller, due to a much-lessened presence of seismic activity, but they are by no means immune. Ray Gibson, staff writer and native Floridian, will discuss that in part two of our special on the risk of tsunamis in the United States.
