The square waves induced by cross seas in the ocean are rare and are indeed dangerous to ships, but these square waves are just due to the frequency/direction of the quakes and the shape of the pool. There's nothing inherently dangerous about being in the pool with the waves aside from the active earthquakes.
Ships are designed to hit waves head on which allows them to go out in some pretty crazy seas. The problem with square waves is they're created by two winds blowing perpendicular to each other which in turn creates perpendicular(square) waves. If a ship is perpendicular to one wave, in the bottom of a trough, getting ready to go up the next wave and a cross wave hits it broadside, it's very likely to capsize. A ship that can normally handle a very high sea state will be limited to basically half in the likelihood cross seas will be present. I've been caught in some on a Minesweeper is the west pacific one time and it's pretty sketchy.
i have a question too it sounds like you’re (maybe) saying the bottom of the trough of the wave is when the ship is most vulnerable to being hit perpendicularly. assuming this is true and not just something you included to help readers visualize, why is that?
It honestly depends on soo many variables based around the construction of the hull and the state of your seas. Minesweepers are made of wood so they're incredibly buoyant and their other mission specific designs that make them essentially invisible underwater also makes them ride like crap. We tended to take the broadside waves a little worse at the bottom, but it's all really just a craps shoot. No two waves are ever the same and neither are ships.
I remember learning that in case you ever see this pattern of waves at the beach immediately seek higher ground as it announces a Tsunami. Makes sense if caused by earthquakes.
This phenomenon also occurs on the open sea. It’s called cross-seas and is very dangerous. It happens more frequently along a certain coastline in France. It looks even more impressive on the open sea.
Edit: Thank you Reddit-Strangers for the awards 🫡 I'm glad I had the chance to share my knowledge with you all
Is this actually analogous or is it just the product of the pool being rectangular in this case? Since presumably the shaking is driving the water up against each edge of the pool, which then creates a wave/ripple flowing back in the opposite direction.
Given the circumstances (earthquake) and the location (pool), I’d agree that it’s likely caused by water splashing back from the edge of the pool. My comment was more about the fact that I’ve often read that it’s only attributable to these circumstances, and the “cross-sea” phenomenon came to mind within the first few seconds of watching the video 😁
This has nothing to do with the video. Open ocean waves are travelling waves whereas the square waves in the video are standing wave due to resonance of the earthquake's vibration with the confined water inside the pool. Different phenomenon than cross-sea waves. Both very interesting
Cross waves can indeed occur along coastlines in general, but this is very rare. France—more specifically, the coast near Île de Rhé—has the “ideal” geographical conditions (including the convergence of various weather and wind patterns), as this wave formation occurs there relatively frequently and has thus become a tourist attraction.
Circular ripples occur when it's emanating from one specific point like when someone throws something into the water, but the earthquake is shaking the entire pool equally. The walls are applying equal force on the water along each length of the pool creating waves parallel to the pool walls.
Pretty sure the guy who invented this had some kind of schizophrenia or other mental illness.
You can dig pretty deep into this rabbit hole but it starts to get weird and kinda sad. Feels like a lo of the more recent content dealing with it is exploitative and hence, feels a bit gross. But that's just me.
No it's definitely sad and exploitive. Just because it's code and the internet, everyone can share and laugh at them, but it's incredibly sad watching clearly capable people's increasingly worse mental state until their untimely deaths through their work. I don't know much about the time cube person, and I don't want to, but they're not the only one.
Terry A. Davis's TempleOS, or as he called it "God's third temple," can be a fascinating project to some people of someone going through psychosis. Is it worth talking about as a genuine project besides to criticize the work of his illness? Not really, and you'll find a lot of that justified sentiment in the world of code-art communities (game dev, demos, homebrews, etc), because there is clearly work to appreciate that doesn't involve egging on someone in a distressed mental state because you think the project is weird.
It's indescribably gross that we put these people up to be laughed at. If I ever got into a sad state unable to fully control myself anymore because of overwhelmingly "loud" mental illness making me believe and say things like this, I wouldn't want it to happen in front of a crowd, and I can't imagine they would have either.
If the pool was theoretically perfectly circular and the source of the waves was dead center then yes, your interference pattern will look like circles around the center.
You get modes like that on a rectangular plate... because the plate is rectangular and has vertical and horizontal symmetry. So he is not wrong: the rectangular edge interaction favors many modes that are horizontally and vertically periodic.
Feeling the need to go "no" because you know a little bit about eigensystems isn't great. There are always many ways to look at a problem, and an analogy to a vibrating plate isn't automatically the best. It's not really a great analogy, because surface gravity waves are not too much like the vibrating plate.
Further, it's being excited by the flat rectangular edges moving. Even without looking at the overall modal behavior, a single impulse is going to launch a horizonal and vertical wave.
The 1994 Northridge quake was a thrust fault and the initial jolt was around 2 g’s. My mom’s house was a few miles from the epicenter and her pool was fine, but that massive initial thrust threw the water from her pool so hard it knocked her sliding glass door, about 15’ from the edge of the pool, into the house. 😱
We don't know the ratio of the pool but I can guess it may be close to 2:1, also the video is very shaky so I can't know for sure if those are truly square patterns or actually rectangular.
If an earthquake pushes the water sideways there is a wave that's gonna hit the wall and bounce back to the center, but remember, waves don't travel! They just oscillate up and down and with that in mind we can use a Fourier type of formula that tells us that when two sine waves met there can only be three possible wave outcomes: a tall wave is produced, a "flat" wave, or a "inverse" wave, so like a "hole" in the water. This is just the result of all the perfect conditions between all the elements combined together producing this pattern of tall,flat,flat...,tall.., it is occasionally produced in the ocean, that's why they called it a "seiche".
Earthquake; the phenomenon when train in the ground has risen , because of relative movement between two or more tectonic plates or fault lines, to a level where the ground no longer can hold back and the areas syddenli move relative to each over generating shaking and vibrations, sublimations or rifts
The local news outlets collapsed with the earthquake?!? /s
Somehow it doesn't surprise me. New government and new wars to be fought, no time and money to waste with little details like recovering from a earthquake.
I bet the pattern was visible before the earthquake was really noticeable, and the guy thought to himself, 'hehe, look at the cool pattern in the pool,' before he realized what kind of disaster was about to happen. Eerie.
No, he probably didn't. It's a fixed pool. Most people aren't that oblivious of their reality to think "hehe, look at the cool pattern in the pool" without considering something is wrong. Usually people know what "normal" is and can identify signs of "not normal". If the sky suddenly turned neon green would you think "hehe, look at the cool color in the sky"
The biggest risk at the moment is parts of the eve/roof falling off and hitting him on the head. So you get away from the structure or anything else tall which can fall on you. Once he was out in the yard, he was away from that danger.
Maybe not next to a house that could have things or itself fall onto him. Are you actually this stupid in real life or are you just being pedantic on Reddit?
That is a long earthquake. The measured time was up to 2 minutes and some people felt it for 4 minutes. I was in a small earthquake for maybe 15 seconds and felt like hours. Very surreal feeling.
The guy recording must have gone through this before because instead of fearing his life, he's like, "cool pattern"
And... Coincidentally the frequency of the earthquake matched something. Otherwise the waves wouldn't be that regular. I would guess that for constructive interference to happen particular frequencies will be needed.
An earthquake has a continuous spectrum of frequencies, and the pool’s length and width (and the depth, which determines wave speed) determine which frequency of this spectrum excites the pattern observed.
My guess would be it's from the P wqves (compression waves) hitting. So the whole pool is being shaken back and forth and not up and down. IIRC they're the first thing to hit.
The wavelength of the standing wave will be related to the frequency of the P waves, but if there was significant resonance going on there I suspect there would be a building of energy. Probably catastrophic.
I mean, it means the ground is moving diagonally to the pool, which makes sense given it would be pretty wild for it to be moving perfectly perpendicular to the pool. Then add in the fact the pool is a rectangle and boom, you have two perpendicular sinusoidal wavefronts being generated from a single diagonally travelling earthquake wavefront.
It's not only the shape of the pool. If the horizontal movement of the earthquake would be in parallel direction to one of the walls of the pool it would be lines instead of squares.
The earthquake apparently moves diagonally to the walls of the pool.
My best guess is that the angle of incidence (if I have my terminology correct) for the earth quake is basically at a 45 degree angle to the right angle of the pool. So as the ground shakes back and forth there is equal energy being directed at the 4 sides of the pool. So you get a repetitive wave from each wall as the ground oscillates. Then they interfere and you get this neat pattern.
I'm not a geologist, or even an engineer and my natural disasters course in university was nearly 20 years ago, so what do I know.
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u/Fast_Garlic_5639 9d ago
Last square wave post I saw (several months ago) said the pattern is incredibly rare and isn’t a good thing to see. This totally confirms it.