28 March 2011
The tsunami at Kesennuma
Video of the sequence of events at Kesennuma changed my entire conception of how a tsunami works. The link discussed at this Reddit thread is now dead, but I think the one I have embedded above is a duplicate; please view today, since I'm not sure whether it will be pulled.
My views of tsunamis had been most strongly influenced by the one in the Indian Ocean in 2004. A memorable video of that event is backed by haunting Breton music by Denez Prigent and Lisa Gerrard. In the Indian Ocean tsunami, the images were of the sea pulling back from the coastline, a giant wave crashing ashore, and then the water retreating and sucking debris and people out to sea.
The Japanese tsunami is different. It's not a giant wave so much as it is the entire ocean moving ashore. In the video above, the water hits - but then it keeps coming and keeps coming and keeps coming. The relentless nature of the onrushing water is jaw-dropping. It seems to me that when the fault line shifted, the seabed offshore from this region must have lifted up (not just shifted horizontally, which might cause a single concussive wave as in the Indian Ocean), and after the seabed rose, the several ?hundred square miles of ocean above the plate must have spilled off to the side and headed outwards, including towards shore.
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That was my reaction, too. That five-minutes-plus-some video starts after the inrush begins and ends before it reverses direction. That's not what I think of when someone ways "wave."
ReplyDeleteHere's a view from a helicopter that shows the sea just deciding to come inland a few miles: http://www.youtube.com/watch?v=eLvuLSeZcp0 Note the highway overpasses that people are running and driving to - I wonder if they were deliberately built as high ground in case of a tsunami.
ReplyDeleteI saw a better version of this same footage a couple of weeks ago, with the original Japanese voice-over. Shock and grief transcend language barriers. I'll try and find it again, but I'm not sure if I can.
I believe this is the one: http://www.youtube.com/watch?v=SWEIOCqYccI There's an annoying number of graphics on the screen, but it's fifteen minutes of unbroken helicopter footage showing water take over a semi-agricultural area. The number of people (in cars and on foot) visible on the footage is frightening, they obviously didn't have time to evacuate everywhere.
ReplyDeleteThat one is also very impressive, Mel.
ReplyDeleteWatching the video that Mel V. provided: I have to say that the disaster presents a more graphic and tradgic presentation when you see cars and people fleeing from what is essentially a wall of water that keeps coming and coming. I don't want to scream censorship here, but most of the footage of the tsunami I have seen in the states, aside from a MSNBC Caught on Camera special show the tsunami going through agricultural lands, not really showing cars or people fleeing from the on-coming wave. I don't know if it's for sensitive reasons, but there's a marked difference in seeing the impact of the tsunami in that video as oppose to some of the other videos I have seen so far.
ReplyDeleteI think my whole concept of a tsunami has changed with the images of the 2004 and 2011 tsunamis. Before then, I was mostly influneced by the look of tsunamis in movies like Deep Impact and other disaster films. In the wake of the tsunami in 2004, I expected filmakers to take from reality, but from 2012, it still looks like a wave rather than what I have seen of tsunamis. As of this moment I have not seen Hereafter, but it does contain a scene related to the 2004 tsunami and earthquake in the Indian Ocean, possibly the first American representation of that event in film to my knowledge. And as I say that, Hereafter has been pulled from Japanese theaters because of this particular scene for sensitive reasons.
My apologies Minnesotan - I was writing up my comments in a hurry at work, I'm afraid they may have come across as one-upmanship, which was not my intent.
ReplyDeleteThe sheer ability of the water to pick up buildings, or crumple them up like corrugated tissue paper, is truly frightening. I've never been comfortable with the idea of living on the shore of a lake, due to irrational fears of the water rising up and swallowing my (theoretical) house. I guess that fear has its roots in some very real events. Odd that my subconscious applies it to lakes instead of oceans, though.
Absolutely no apologies necessary, Mel. I just meant to say the one you found is impressive, but not the one I had seen before. I'm glad you posted it. Thankx.
ReplyDeleteThe seabed did lift up: fifty feet, which is an extraordinary shift for an earthquake. And over a fault line rupture of at least 200 miles, that displaces a Whole. Lot. Of. Water.
ReplyDeleteAnother good video that shows the speed at which everything got overwhelmed.
ReplyDeletehttp://www.youtube.com/watch?v=ijuwl1Zw7s0
Didn't the coast drop several feet as well?
ReplyDeleteAt any rate, those videos were terrifying.
I used to teach a class on wave dynamics, and tsunamis were by far the most fascinating aspect. What confuses people is that Hollywood always shows the same type of tsunami: the towering, single wave event. But tsunamis are extremely variable, depending on the cause (side slip earthquake, upthrust earthquake, undersea landslide, meteorite, etc), the distance traveled, and the topography/bathymetry of the coastal areas it hits. Most tsunamis, like most earthquakes, aren’t even detectable without precision instruments. They’re just tiny rises in sea level that blend in with normal tide fluctuations. And they are almost never single waves, but a series of them, in which the first is not necessarily the largest.
ReplyDeleteTsunamis can indeed occur in lakes, if the lake lies on a fault line or if it’s surrounded by towering mountains that can generate a big enough rock fall. The biggest tsunami ever recorded did not come from the ocean, but was generated inside an Alaskan bay. Google “Lituya Bay tsunami 1958” to get your mind blown -- the wave reached a top height of 1,720 feet. The measurement was easy to make, because that was the highest point at which the surrounding mountains were stripped of all trees and vegetation.
Stan, you’re right about the nature of the Japan tsunami -- it was indeed a huge section of ocean sliding off a sudden upthrust. Water is self-leveling, and that is the underlying principle of all tsunamis. The other aspect of tsunamis that most people are unaware of is their long periods. For instance, a strong winter storm wave on the Oregon coast can easily be 40 feet high. But once it arrives to the shore, it crashes, runs up a bit and immediately retreats as the next one comes in. That distance between two consecutive wave troughs is called a period, and wave periods are normally measured in seconds.
But a tsunami wave has a period measured in tens of minutes, and often more than an hour. That is why a 40-foot storm wave is no big deal, while a mere 9-foot tsunami can cause astonishing destruction. Because the water just keeps coming.
Thank you, Fletcher, for a very informative comment. I'll take this opportunity to let other readers know that Fletcher maintains his own interesting blog at "Oregon Expat" -
ReplyDeletehttp://oregonexpat.wordpress.com/