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M8.7 earthquake in Western Pacific, tsunami warning issued

earthquake.usgs.gov

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Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#131

Post by bonzini »

andoando wrote: post #108
VintageCool wrote: post #95

Earlier quoted context omitted.

I remember in 2015 watching this great tsunami video at a harbor. It was about 11 minutes long. At the start, there's just a white line at the horizon. Then the fishing boats in the harbor start rocking and jangling. Then water starts pouring over some walkways and sea walls. Eventually the cameraman backs away and starts climbing a concrete tower; water starts to flood over the area where they had been standing. I t…

It never got above the boats, cant be more than a few feet tall

The port's wall slow down the entry of the water and the boats can float. The "tide" caused by the tsunami was several meters.

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#132

Post by bee_rider »

ninetyninenine wrote: post #114
crystal_revenge wrote: post #98

Earlier quoted context omitted.

I'm surprised so many people don't understand what tsunamis are. It's a "wave" created by a sudden shift in the Earth's crust. Imagine, suddenly, water on each of side of that split is now at different heights and has to equalize. It's much closer to just removing a dam that is holding back water equal in height to the new difference between the sea floors. What you get is not a "wave" but a wall of water.

This doesn't make sense to me intuitively. It must be a wave. Imagine you have a fault line. There is a left side and a right side to the fault line. If the left side lowers with a shift then that shift MUST be localized to the area around the fault. Because if it wasn't then that means there's an elevation change across the board for everything to the left of the fault. You see how that doesn't make sense? So if the…

Yeah, they are waves I think. Just, really incredibly big waves with lots of mass behind them. I think people want to say “not a wave” to emphasize the fact that they are much bigger than the waves that the local environment is used to, so they can be really surprising.

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#133

Post by sugarpimpdorsey »

derefr wrote: post #128
timr wrote: post #123

Earlier quoted context omitted.

That makes sense, though. To do otherwise would be pretty dumb for a tsunami situation. But yeah, the handheld telephoto zoom from a safe location is definitely on the Japanese Disaster TV bingo card. That said, I appreciate that they just keep repeating the same warnings and data, rather than the ridiculous speculation that the US news media engages in when they get bored.

I mean, they could at least fly some drones over to the beach for some B-roll.

It would take too long to fax back the Ultra HD footage taken with optics we can't even comprehend exist.

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#134

Post by throwaway290 »

ninetyninenine wrote: post #114
crystal_revenge wrote: post #98

Earlier quoted context omitted.

I'm surprised so many people don't understand what tsunamis are. It's a "wave" created by a sudden shift in the Earth's crust. Imagine, suddenly, water on each of side of that split is now at different heights and has to equalize. It's much closer to just removing a dam that is holding back water equal in height to the new difference between the sea floors. What you get is not a "wave" but a wall of water.

This doesn't make sense to me intuitively. It must be a wave. Imagine you have a fault line. There is a left side and a right side to the fault line. If the left side lowers with a shift then that shift MUST be localized to the area around the fault. Because if it wasn't then that means there's an elevation change across the board for everything to the left of the fault. You see how that doesn't make sense? So if the…

> If the left side lowers with a shift then that shift MUST be localized to the area around the fault. Because if it wasn't then that means there's an elevation change across the board for everything to the left of the fault. You see how that doesn't make sense

Yo heard of fluid dynamics? Good luck localizing this;) maybe you can build a wall or something real quick

Obviously it is all technically waves. Even if EVERYTHING to the left lowered we would be talking about waves caused by it. But it don't need to be all lowered because waves propagate. And point is these particular waves, tsunami are not the waves you think about because you saw some on the beach. It's an ocean rising for a while. Watch some vids to get a vibe for it.

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#135

Post by MPSimmons »

andoando wrote: post #108
VintageCool wrote: post #95

Earlier quoted context omitted.

I remember in 2015 watching this great tsunami video at a harbor. It was about 11 minutes long. At the start, there's just a white line at the horizon. Then the fishing boats in the harbor start rocking and jangling. Then water starts pouring over some walkways and sea walls. Eventually the cameraman backs away and starts climbing a concrete tower; water starts to flood over the area where they had been standing. I t…

It never got above the boats, cant be more than a few feet tall

I feel like you're making a bad joke. Did you drop your /s?

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#136

Post by [deleted] »

timr wrote: post #123
decimalenough wrote: post #116

Earlier quoted context omitted.

Also, the very first thing they say when the camera cuts to them is that they are standing in designated evacuation zone X that's Y meters above sea level. Then the cameraman zooms at the ocean, which is blurry and shaky because they're in the designated evacuation zone Z km away from the coast.

That makes sense, though. To do otherwise would be pretty dumb for a tsunami situation. But yeah, the handheld telephoto zoom from a safe location is definitely on the Japanese Disaster TV bingo card. That said, I appreciate that they just keep repeating the same warnings and data, rather than the ridiculous speculation that the US news media engages in when they get bored.

[deleted]

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#137

Post by nessex »

crystal_revenge wrote: post #98
hsbauauvhabzb wrote: post #54

Earlier quoted context omitted.

Is height the only thing that matters? Presumably 1x 2m wave is less impactful than 10 x 1m waves spread 20 seconds apart?

I'm surprised so many people don't understand what tsunamis are. It's a "wave" created by a sudden shift in the Earth's crust. Imagine, suddenly, water on each of side of that split is now at different heights and has to equalize. It's much closer to just removing a dam that is holding back water equal in height to the new difference between the sea floors. What you get is not a "wave" but a wall of water.

Not true. As the news reporters here in Japan are repeating every few minutes, there will be many waves and they can get bigger over time. They already have, 20-30cm initial waves had 40-60cm later waves.

Waves can get bigger due to earthquakes not being instantaneous or necessarily a single movement, due to amplification by geography, by reflections, by aftershocks, and many other things. The news is suggesting waves lasted about a day for a previous event in a similar area.

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#138

Post by K0balt »

ninetyninenine wrote: post #130
TylerE wrote: post #79

Earlier quoted context omitted.

Despite the common vernacular calling them "waves" they're really more like really really high tides. You're talking about something that happens over, say, 10-90 minutes, not seconds.

These things are 100% waves. It's not a misnomer. It fits the scientific definition of waves and it fits our intuition of what waves are. These are NOT tides. https://www.noaa.gov/explainers/science-behind-tsunamis

Yes, they are waves, but they are often very long waves. A typical 1m wave might be 20m long. A tsunami wave might be a kilometer long or longer. That is why people say they are like a tide. The wave arrives, then does not recede for several minutes. So, while a 4m wind driven wave might break over a seawall and even wash a car off the road, a 4m tsunami washes ships over that same seawall and floods the city.

It’s a wave, but it is often not at all like a regular ocean wave. I’ve been at sea when a 3m tsunami passed, we barely felt it. If it had been a 3m wind wave in that otherwise calm sea, it would have knocked dinner off the table.

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#139

Post by K0balt »

tracerbulletx wrote: post #129
TylerE wrote: post #79

Earlier quoted context omitted.

Despite the common vernacular calling them "waves" they're really more like really really high tides. You're talking about something that happens over, say, 10-90 minutes, not seconds.

They are very literally long wavelength waves though.

Yes, they are waves, but they are often very long waves. A typical 1m wave might be 20m long. A tsunami wave might be a kilometer long or longer. That is why people say they are like a tide. The wave arrives, then does not recede for several minutes. So, while a 4m wind driven wave might break over a seawall and even wash a car off the road, a 4m tsunami washes ships over that same seawall and floods the city.

It’s a wave, but it is often not at all like a regular ocean wave. I’ve been at sea when a 3m tsunami passed, we barely felt it. If it had been a 3m wind wave in that otherwise calm sea, it would have knocked dinner off the table.

Re: M8.7 earthquake in Western Pacific, tsunami warning issued

#140

Post by K0balt »

ninetyninenine wrote: post #114
crystal_revenge wrote: post #98

Earlier quoted context omitted.

I'm surprised so many people don't understand what tsunamis are. It's a "wave" created by a sudden shift in the Earth's crust. Imagine, suddenly, water on each of side of that split is now at different heights and has to equalize. It's much closer to just removing a dam that is holding back water equal in height to the new difference between the sea floors. What you get is not a "wave" but a wall of water.

This doesn't make sense to me intuitively. It must be a wave. Imagine you have a fault line. There is a left side and a right side to the fault line. If the left side lowers with a shift then that shift MUST be localized to the area around the fault. Because if it wasn't then that means there's an elevation change across the board for everything to the left of the fault. You see how that doesn't make sense? So if the…

Yes, they are waves, but they are often very long waves. A typical 1m wave might be 20m long. A tsunami wave might be a kilometer long or longer. That is why people say they are like a tide. The wave arrives, then does not recede for several minutes. So, while a 4m wind driven wave might break over a seawall and even wash a car off the road, a 4m tsunami washes ships over that same seawall and floods the city.

It’s a wave, but it is often not at all like a regular ocean wave. I’ve been at sea when a 3m tsunami passed, we barely felt it. If it had been a 3m wind wave in that otherwise calm sea, it would have knocked dinner off the table.

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