New tsunami advisory warning - Japan
More information from http://www.jma.go.jp/en/tsunami/ Andrew
Re: New tsunami advisory warning - Japan
On Sun, 27 Mar 2011 15:46:24 PDT, "andrew.wallace" said: > More information from http://www.jma.go.jp/en/tsunami/ Has expired already, but only predicted a 0.5 meter crest. http://www.jma.go.jp/en/tsunami/info_04_20110328072748.html *yawn*. A foot and a half isn't going to be all *that* bad unless focused by some very strange local geography. pgpYVvBglnztW.pgp Description: PGP signature
Re: New tsunami advisory warning - Japan
On Mon, Mar 28, 2011 at 1:59 AM, wrote: > *yawn*. A foot and a half isn't going to be all *that* bad Remember a wall of tsunami water travels in general at approx 970 kph (600 mph), think about it.
RE: New tsunami advisory warning - Japan
> *yawn*. A foot and a half isn't going to be all *that* bad Sorry to continue off topic: Try to imagine ... a temporary very high tide, rather than a cresting wave. In addition to the "height", it's the wave-length you have to take into account. Tsunami's rarely become towering breaking waves. [That said, tsunamis can form into a bore - a step-like wave with a steep breaking front. Likely if the tsunami moves from deep water into a shallow river / bay] 1 1/2 foot on top of an existing high tide, could easily cause further flooding in the wrong locations (although as mentioned, not to the levels already experienced). > travels in general at approx 970 kph (600 mph) True in the deepest parts of open ocean - upon reaching the shore-line it'll be travelling a lot slower. // Gav
Re: New tsunami advisory warning - Japan
On Mon, Mar 28, 2011 at 11:43 AM, Gavin Pearce wrote: >> travels in general at approx 970 kph (600 mph) > > True in the deepest parts of open ocean - upon reaching the shore-line > it'll be travelling a lot slower. You guys forget a lot of folks on the list are working on cabling ships and off shore platforms, its not all about what happens on shore in this industry. Andrew
Re: New tsunami advisory warning - Japan
Gavin Pearce wrote: *yawn*. A foot and a half isn't going to be all *that* bad Sorry to continue off topic: Try to imagine ... a temporary very high tide, rather than a cresting wave. In addition to the "height", it's the wave-length you have to take into account. Tsunami's rarely become towering breaking waves. Quite right. The other part is that the water becomes a very fast moving river, especially in places where it's not normally one. Watching the footage from the Santa Cruz harbor it wasn't the height that was a particular problem, but the fact that all of a sudden you had a 5-10 knot current. And this happened at low tide, so it would have been far worse if it happened at high tide. There was a pretty spectacular photo of the tsunami that appeared to be around the Emeryville flats. Only about 6 or so inches high, but massive. Had it been at high tide, it could have probably done some nasty things... like, oh for example, the sewage treatment plant next to the Bay Bridge comes to mind. Mike
RE: New tsunami advisory warning - Japan
> You guys forget a lot of folks on the list are working on cabling ships and > off shore platforms, its not all about what happens on shore in this industry. Valid point ... however in deep ocean, these things are pretty imperceptible. The effect on ships on the surface are nominal, and off shore platforms are (generally) built with these things in mind: http://www.msnbc.msn.com/id/27324535/ns/technology_and_science-innovation/ At the other extreme, Lituya Bay is a good example of a Mega Tsunami (1,720 feet): http://en.wikipedia.org/wiki/1958_Lituya_Bay_megatsunami
Re: New tsunami advisory warning - Japan
On Mar 28, 2011, at 10:57 AM, Gavin Pearce wrote: >> You guys forget a lot of folks on the list are working on cabling ships and >> off shore platforms, its not all about what happens on shore in this >> industry. > > > > Valid point ... however in deep ocean, these things are pretty imperceptible. > The effect on ships on the surface are nominal, and off shore platforms are > (generally) built with these things in mind: > http://www.msnbc.msn.com/id/27324535/ns/technology_and_science-innovation/ > Here is a video of the recent Japanese tsunami from a JCG ship in the the open ocean. The waves (@ ~4:20 and 6:40 into the video) caused them no trouble, but they were certainly not imperceptible. Regards Marshall > > > At the other extreme, Lituya Bay is a good example of a Mega Tsunami (1,720 > feet): > > http://en.wikipedia.org/wiki/1958_Lituya_Bay_megatsunami > > > > > > > > > > > > >
Re: New tsunami advisory warning - Japan
On Mar 28, 2011, at 11:28 AM, Marshall Eubanks wrote: > > On Mar 28, 2011, at 10:57 AM, Gavin Pearce wrote: > >>> You guys forget a lot of folks on the list are working on cabling ships and >>> off shore platforms, its not all about what happens on shore in this >>> industry. >> >> >> >> Valid point ... however in deep ocean, these things are pretty >> imperceptible. The effect on ships on the surface are nominal, and off shore >> platforms are (generally) built with these things in mind: >> http://www.msnbc.msn.com/id/27324535/ns/technology_and_science-innovation/ >> > > Here is a video of the recent Japanese tsunami from a JCG ship in the the > open ocean. The waves (@ ~4:20 and 6:40 into the video) caused them no > trouble, but they were certainly not imperceptible. > With the video : http://www.youtube.com/watch?v=4XSBrrueVoQ&feature=player_embedded#at=19 Marshall > Regards > Marshall > >> >> >> At the other extreme, Lituya Bay is a good example of a Mega Tsunami (1,720 >> feet): >> >> http://en.wikipedia.org/wiki/1958_Lituya_Bay_megatsunami >> >> >> >> >> >> >> >> >> >> >> >> >> > > >
RE: New tsunami advisory warning - Japan
> JCG ship in the the open ocean. Impressive video. The wave height and speed would suggest shallower waters, and that likely the ship was close to land mass when the video was filmed rather than open ocean (in the sense of being far out to sea). Not being there of course I could easily be incorrect. Anyway we digress :) Gav On Mar 28, 2011, at 11:28 AM, Marshall Eubanks wrote: > > On Mar 28, 2011, at 10:57 AM, Gavin Pearce wrote: > >>> You guys forget a lot of folks on the list are working on cabling ships and off shore platforms, its not all about what happens on shore in this industry. >> >> >> >> Valid point ... however in deep ocean, these things are pretty imperceptible. The effect on ships on the surface are nominal, and off shore platforms are (generally) built with these things in mind: http://www.msnbc.msn.com/id/27324535/ns/technology_and_science-innovatio n/ >> > > Here is a video of the recent Japanese tsunami from a JCG ship in the the open ocean. The waves (@ ~4:20 and 6:40 into the video) caused them no trouble, but they were certainly not imperceptible. > With the video : http://www.youtube.com/watch?v=4XSBrrueVoQ&feature=player_embedded#at=19 Marshall > Regards > Marshall > >> >> >> At the other extreme, Lituya Bay is a good example of a Mega Tsunami (1,720 feet): >> >> http://en.wikipedia.org/wiki/1958_Lituya_Bay_megatsunami >>
Re: New tsunami advisory warning - Japan
On Mar 28, 2011, at 1:03 PM, Marshall Eubanks wrote: > > On Mar 28, 2011, at 11:28 AM, Marshall Eubanks wrote: > >> >> On Mar 28, 2011, at 10:57 AM, Gavin Pearce wrote: >> You guys forget a lot of folks on the list are working on cabling ships and off shore platforms, its not all about what happens on shore in this industry. >>> >>> >>> >>> Valid point ... however in deep ocean, these things are pretty >>> imperceptible. The effect on ships on the surface are nominal, and off >>> shore platforms are (generally) built with these things in mind: >>> http://www.msnbc.msn.com/id/27324535/ns/technology_and_science-innovation/ >>> >> >> Here is a video of the recent Japanese tsunami from a JCG ship in the the >> open ocean. The waves (@ ~4:20 and 6:40 into the video) caused them no >> trouble, but they were certainly not imperceptible. >> > > With the video : > > http://www.youtube.com/watch?v=4XSBrrueVoQ&feature=player_embedded#at=19 Didn't show much and they were near the epicenter. My friend was on her 44' sailboat about halfway between Galapagos and Easter Island went Chile's earthquake happened which caused a 10' tsunami in the Galapagos. They never noticed a thing. Tom Tom
Re: New tsunami advisory warning - Japan
On 03/28/2011 01:22 PM, Gavin Pearce wrote: >> JCG ship in the the open ocean. > Impressive video. The wave height and speed would suggest shallower > waters, and that likely the ship was close to land mass when the video > was filmed rather than open ocean (in the sense of being far out to > sea). Not being there of course I could easily be incorrect. > > Anyway we digress :) > > Gav > > On Mar 28, 2011, at 11:28 AM, Marshall Eubanks wrote: > >> On Mar 28, 2011, at 10:57 AM, Gavin Pearce wrote: >> You guys forget a lot of folks on the list are working on cabling > ships and off shore platforms, its not all about what happens on shore > in this industry. >>> >>> >>> Valid point ... however in deep ocean, these things are pretty > imperceptible. The effect on ships on the surface are nominal, and off > shore platforms are (generally) built with these things in mind: > http://www.msnbc.msn.com/id/27324535/ns/technology_and_science-innovatio > n/ >> Here is a video of the recent Japanese tsunami from a JCG ship in the > the open ocean. The waves (@ ~4:20 and 6:40 into the video) caused them > no trouble, but they were certainly not imperceptible. > With the video : > > http://www.youtube.com/watch?v=4XSBrrueVoQ&feature=player_embedded#at=19 Thanks for the link... Very impressive, though strong storm waves get higher. This is not an open-ocean tsunami, it is probably either direct from the quake source or reflected from the nearby coast (I'm fairly sure it is the latter, though there isn't a good time reference in the video, since there appears to be land visible in the frame; if the white mass is really land, this definitely does not qualify as open-ocean, which for tsunami purposes has to be an open-ocean wavelength or so from the nearest land or shallow water (600-800 miles; you wouldn't see the land...) Cable damage from tsunamis mostly comes from bulk motion up or down a sloping ocean bottom, or from primary or secondary turbidity currents (basically an underwater avalanche) (unless you are unlucky enough to have the fault break itself cut the cable; this isn't too likely but with this fault geometry it could have happened.) Also, this quake (the 8.9 "main" one, not either the foreshocks or aftershocks, several of each were strong enough to trigger a tsunami watch in Hawaii by themselves) had a very extended energy-release time; the ground motion went for several minutes (see the graph in http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/finite_fault.php). That can complicate wave generation a lot. Various mechanisms contribute to tsunami generation; the majority of wave generation in the 1960 Chile event came from landslides secondary to the main earthquake (which was very deep and centered under land...) My memory of papers about the 1964 Alaska quake involved both ground motion and landslides as contributors. Note that in this case, the resulting waves can go different directions from the same quake. Aside: I worked for the U of Hawaii tsunami reasearch program in the 1960's for a while, we were mainly working on very early prototypes of the deep-ocean pressure sensors that are now deployed. Decent embedded microprocessors didn't exist then (for that matter, *any* microprocessors, even the 1802 or 8008, either of which would have been a grand luxury :-( Those finally made these sensors practical. (ours was set up with a write-only 7-track tape drive, using discrete-transistor logic modules (no practical ICs yet either). It was to be placed on Ocean Station November (about 2/3 of the way from San Francisco to Honolulu), kicked overboard on request from the research people (after a "suitable" earthquake), then retrieved using a low-power radio beacon a few days later when the cable release timer tripped.) Modern electronics has improved things :-) -- Pete > Marshall > > >> Regards >> Marshall >> >>> >>> At the other extreme, Lituya Bay is a good example of a Mega Tsunami > (1,720 feet): >>> http://en.wikipedia.org/wiki/1958_Lituya_Bay_megatsunami This one lists landsliding (or perhaps calving) as the generation mechanism, and both the source and the bay outlet were small enough that the wave probably didn't propagate too far once in the open ocean. > > >
Re: New tsunami advisory warning - Japan
Michael Thomas wrote: Gavin Pearce wrote: *yawn*. A foot and a half isn't going to be all *that* bad Sorry to continue off topic: Try to imagine ... a temporary very high tide, rather than a cresting wave. In addition to the "height", it's the wave-length you have to take into account. Tsunami's rarely become towering breaking waves. Quite right. The other part is that the water becomes a very fast moving river, especially in places where it's not normally one. Watching the I don't underestimate the power of even a small tsunami. I have friends rendered homeless by the Santa Cruz tsunami (their boat being their only home). Though I can understand one is underwhelmed by a mag 6.x earthquake in that region considering I believe more than 20 6+ ones happened there since the first mag 7.2 earthquake that happened 2-3 days before the mag 9 one. Most recent ones: http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/145_40_eqs.php -- http://goldmark.org/jeff/stupid-disclaimers/ http://linuxmafia.com/~rick/faq/plural-of-virus.html
Re: [v6z] Re: New tsunami advisory warning - Japan
On Sun, Mar 27, 2011 at 6:28 PM, andrew.wallace < andrew.wall...@rocketmail.com> wrote: > On Mon, Mar 28, 2011 at 1:59 AM, wrote: > > *yawn*. A foot and a half isn't going to be all *that* bad > > Remember a wall of tsunami water travels in general at approx 970 kph (600 > mph), think about it. > That's in deep water, where the height of the wave might be a few inches at most. Once it reaches shallow water the speed drops significantly and the height increases. Scott
Re: [v6z] Re: New tsunami advisory warning - Japan
And then you can have lens effects, where the waves reflections on the coast, focus unto a point on the coastline. On 3/28/11 14:34 , "Scott Howard" wrote: >On Sun, Mar 27, 2011 at 6:28 PM, andrew.wallace < >andrew.wall...@rocketmail.com> wrote: > >> On Mon, Mar 28, 2011 at 1:59 AM, wrote: >> > *yawn*. A foot and a half isn't going to be all *that* bad >> >> Remember a wall of tsunami water travels in general at approx 970 kph >>(600 >> mph), think about it. >> > >That's in deep water, where the height of the wave might be a few inches >at >most. > >Once it reaches shallow water the speed drops significantly and the height >increases. > > Scott
