Thailand Tsunamis

[claymore]

Probably a very dumb question but did the waves only go northish with this thing or was something felt on the Australian coast. I was thinking about whether or not Ellen Macarthur or the Vendee fleet might have felt the effects of it. I suppose they are beyond its reach?

 

[Joe_Cole]

I was wondering the same. In deep water though it would pass by unnoticed (Particularly in the conditions she has been sailing in)

 

[webcraft]

I think that if you are in deep water you won't even notice it as it is a pure wave motion with no 'sideways' forces associated with it. It is also likely to only be a foot or so high and with a long wavelength. It is only when the wave hits shallow water that it becomes dangerous.

I see the Scotsman today has an article calling for an early warning system for the Atlantic. If the predicted Las Palmas volcanic landslip happened the S. Coast could expect 30ft waves.

- Nick

 

[Ships_Cat]

Apparantly 20cm was recorded on NZ's western coastline - that is if the news media reported it correctly, which is always a worry. We live right on that coast and, of course, did not notice a thing.

As far as I know tsunamis are not noticable by normal means from a boat in deep water.

John

 

[BrendanS]

The waves will go out in a circle from the epicentre, same as the ripples from a stone dropped in a pond. Only a rough circle though, as the epicentre was a long line, not a point. Ellen is in deep water, so effects would be minimal - she's probably not totally beyond it's reach, as even African shore line has been affected

 

[longjohnsadler]

Assume that as the epicentre was off the northern tip of Sumatra, anything further to the south ie Australia was effectively in the 'shadow' of Sumatra and therefore didn't experience the same effect?

 

[jonjo]

CNN TV showed a video clip of the wave pattern flowing across the Indian Ocean, it had enough random features to indicate it was taken from space i.e. not a computer model.

The wave pattern was not regular or circular. The strongest wave front was linear and moved due west.

 

[Bergman]

I would suggest that the Scotsman had a good point

There is a fault line runs roughly N-S down the Atlantic and a history of volcanic activity from Iceland southwards.

Also worth mentioning that the Eastern Atlantic is well monitored by sonar sensors so a warning system should be relatively easy to set up.

Exactly what one would do if there was a warning is another matter. Thinking back to the floods of 2000 in my area, the performance of local authority emergency planners was not impressive, how they would cope with something on this scale is anybodies guess.

 

[Mahi]

Deep water sailors would not typically notice any effect from a tsunami. Though I am sure that I did once observe a very strange shaped swell while crossing the N. Pacific some years back, but no solid proof there.

Here is a link of a model showing propagation of the Asian Tsunami

I have just heard a radio bulletin which said that a plane had flown over N.Sumatra and there is 'nothing left' of the towns - at all.....

 

[Ships_Cat]

Has been confirmed by the marine sciences people here that the remnants of the tsunami were recorded on NZ's western coastline tidal gauges and varied between 10 and 30 cm. They say the tsunami had to travel around 8,000km to get here and did so in 17 hours (470 kilometers per hour).

There is a well established tsunami warning system in the Pacific Ocean and many are now jumping in and saying the same should be set up for the Indian Ocean. However, scientists here are saying that would not be of much use as the Indian Ocean is too small - the most warning that could be gotten would be a couple of hours which is not long enough to get warnings out to people and evacuate. I suspect that would also be so for other vulnerable areas such as the Med.

Whereas in the Pacific the distances are large enough for countries well away to get useful warning. Even as a child (many moons ago and we lived on the coast) I can remember us being taught what the town's warning siren signal was. Today, inside cover of every copy of the telephone yellow pages is a "what do do" if there is a tsunami warning. In my lifetime here I have only experienced one tsunami warning, and while the effects were observable it was a "fizzer" luckily.

John

 

[Mahi]

[ QUOTE ]
However, scientists here are saying that would not be of much use as the Indian Ocean is too small - the most warning that could be gotten would be a couple of hours which is not long enough to get warnings out to people and evacuate.

[/ QUOTE ]

How sad that some scientists are talking this way already. Any warning is surely better than no warning at all. Coupled of course with education about what and what not to do.

Ironic too, because there are plenty of other kinds of natural hazards (large and small scale), which have a very short warning time (< 1 hr or so). There are many examples, but one that immediately comes to mind is a 'lahar' (volcanic mud-flow). There are warning systems for lahar hazards in NZ and elsewhere and they would in most cases give far less warning time than 1 hr. Yes, a lahar event would be on a smaller scale, but I still find it dismissive of anyone to say that a tsunami warning system would not be worth installing for the Indo/Asian region /forums/images/graemlins/frown.gif.

 

[ShipsWoofy]

How deep?

Would you have to be off the continental shelf or would 100m be ok. In another thread we heard the family of one forumite headed out into deeper water and survived.

Does anyone know where the cut off would be?

An example, a tidal wave is on its way toward Cornwall from the Canaries, so as many Cornish boaters start heading towards the Atlantic, would they get deep enough to be out of danger if they had say 3 - 4 hours?

Do you get a wind with a tidal wave, that much water shifting must bring with it strong winds, surely?

 

[Ships_Cat]

I'll leave it up to you as to how once you have detected (how? in deep water) or assume that there is a tsunami travelling at 500+ km/hour you effectively determine who will be in its path and warn them and then have them evacuating all within an hour (or minutes for those closest).

The two hours for the Indian Ocean is to the likely affected countries from a tsunami originating on the "ring of fire" side and for beyand that travelling to Africa is far enough away for a warning to likely not be needed. For a tsunami originating in the "ring of fire" the time from the earthquake to the tsunami hitting populated areas of S and SE Asia was from within much less than an hour up to an hour according to the link you posted. Beyond the hour travel distance there was not much damage. (Although news media say 2-1/2 hours to Ceylon which is contrary to the link model).

Sounds all superficially caring and wishy washily nice to have the system but I would suggest that it would be of little worth.

As you say there are lahar warning systems but they are very localised systems serving small highly controlled areas with low populations (or as in NZ no habitation at all) in the path of a lahar - they only cover of order of a few 10's of miles at most. There is obviously no lahar warning system that covers an area anything comparable at all in extent to the shores of even a small sea and across diverse nations, many with poor communication facilities or little uptake of those by the population.

As I said, NZ is a partner in the Pacific warning system, however that only provides comfort if the initiating earthquake is thousands of miles away. Even though we personally live in an exposed position, I would doubt that we would get to even hear of any tsunami before it hit if it originated 2 hours away (especially so as there is no significant land within 2 hours propagation distance of NZ).

Your design of the system will be interesting.

John

 

[Mahi]

Clearly not everyone will receive a warning in time; many 1000's of lives will still no doubt be lost. But scientists at the USGS (US Geological Survey) or some similar organisation attempted desperately to alert authorities, but were frustrated by the lack of any emergency communication system. There are already systems in place for the Pacific using data buoys, satellite data plus a communications system. But in this case, the geophysicists involved, very quickly had all the info they needed to know that a tsunami was inevitable - they were right. Their (USGS geophysicists) sense of humanity took over. Sadly they were frustrated by a lack of a communication system.

Had a communication system been in place to a network of civil defence agencies, then perhaps, *some* (certainly not all!) lives could have been saved. Perhaps, if the one life that was saved was your relative you might view matters differently. We live in the era of fast telecommunications - such a system would cost but would surely not be impossible economically or strategically.

Of course it won't save everyone, but any effort is surely worth it and anything but 'wishy-washy'!

On behalf of the 10's of 1000s who have died or been injured and displaced I would, (if it were me), be looking at all possibilities before dismissing it so soon after the event. Thank goodness not all scientists take such a pessimistic viewpoint.

 

[Ships_Cat]

I think you are overwhelmed by public misinformation. You should do a Google and look for the Pacific Tsunami Warning System internet site in Hawaii (operated by NOAA).

You will find nothing about satellites, data buoys, etc there. You will find that they say that they cannot (and is not possible to) detect a Tsunami until the first surge reaches land with a monitored tidal station or similar. By then it is obviously too late for that location but not for land still in the path of the Tsunami but far enough away to enable a useful warning time before the wave propagates there.

They try to predict tsunamis by analysing the P, S and Love and Raleigh surface waves of large earthquakes picked up at a number of observatories. So, first the waves travelling through the earth surface have to propagate to several observatories (some take chordal shortcuts), during which time the tsunami is also racing out at 500 to 1,000 km/hr, about 1/30th or so of the speed of the P wave and maybe 1/10 -1/15 the the speed of the surface waves.

Then they have to be analysed to determine the earthquake's location (from the P and S waves) and strength (from the surface waves) and then determine if the earthquake was a shallow uplifting one or not (the uplifting ones may cause tsunamis), and if there is a risk of tsunami.

Obviously all that takes time.

One may say to short circuit all that and just shout "run" everytime there is a biggish earthquake. I do not know where you live, but if that approach was taken where we live then we would be evacuating our house here very frequently (there have been 2 earthquakes with magnitudes greater than 7 within about 1,000 km over the last 5 weeks or so and we regularly have smaller ones out to sea within a few hundred km of here).

Despite the system in the Pacific and the long propagation distances allowing greater warnings for many, I doubt whether there is much useful warning for most tsunamis unless of sufficient magnitude to be of Pacific wide influence as the large earthquakes mainly occur along the "rim of fire" and up the Americas - so tsunamis will inundate the countries close by with little or no warning (as happened in Chile, 1960), and then in most instances the distances are so great across remaining ocean to other land masses that the tsunami is attenuated.

The last Pacific wide one was in 1960 which originated in Chile and that is the one I can remember the warnings as a kid for. There were deaths as far away as Japan (couple of hundred and 17,000km away) and Hawaii (60 odd and 10,000km away) - as in the Indian Ocean one, most deaths were close by and for which no warning was possible.

They are very rare events and public education cannot be easily sustained between them, even in a small country with good communications like here in NZ. There is no way many would know or react in time to evacuate from most tsunamis here in NZ despite the system, but there would be many that would recognise the first surge signs if on a beach but by then it is probably too late unless they have immediate access to higher land.

It may be that through public opinion some sort of Indian Ocean wide region system will be put in, but it will be in the main ineffectual, and because of the low frequency of significant region wide events would be unlikely to be tested severely in our lifetimes. It certainly will not make any difference to the more frequent deaths from non region wide tsunami events such as those over the last decade in Japan, New Guinea, etc.

I think that maybe you do not appreciate what these things are like. It is dismissive of you to accuse scientists trying to give a realistic understanding of the merits as just being pessimistic.

John

 

[Mahi]

Hello John, sorry, but I am certainly not 'overwhelmed by public misinformation', neither my location (not too far from you probably), nor my background allow this.

As previously mentioned, scientists from several agencies (including Pacific Tsunami Warning Center and the USGS etc) knew very quickly everything they needed to know to make an educated assessment of the reality of the situation.

link # 1 as an example.

and also this

link # 2

I do very much understand a scientist's need for factual information. Obviously you are entitled to your viewpoint. However, it would appear that I am looking at the matter from a different point of view to you. A viewpoint that is apparently shared by the Director of the USGS, Waverly Person as well as those from the Pacific Tsunami Warning Center as shown by the quote below and the links above.

......"A warning center such as those used around the Pacific could have saved thousands of lives, Waverly Person of the U.S. Geological Survey's National Earthquake Information Center, told Reuters".....

 

[claymore]

Its really funny watching the pattern of this conversation. There is considered opinion with researched, scientific verification, justifying and supporting the stated facts. Reasoned counter argument follows, then in the very last paragraph of each response comes the zapline! 'Obviously you don't consider scientists are worth their morning egg'..... 'It is unfortunate that scientists are pragmatic to the point of hating their mothers'

I'm marking some Degree exams just now - you bring me welcome relief, don't stop!

 

[jonjo]

> you bring me welcome relief, don't stop!

How about a Tsunamis expert called Mr Waverly Person? In any other context I would suspect a wind-up.

 

[Mahi]

You lot are funny /forums/images/graemlins/smile.gif! Now, I am all out of puff and will have to go away and re-stoke my boiler! However, may I add that I would insert the word 'some' before 'scientists' in both your rather well put summary statements Claymore. /forums/images/graemlins/grin.gif

As for Waverly Person...., definitely not a wind up - promise! /forums/images/graemlins/tongue.gif

 

[Ships_Cat]

I think if you look at the locations of big earthquakes, the times those you refer to are talking about (assuming they are correctly quoted) and add the time for mobilisation to get the first warnings out (30 minutes here), and then for those hearing the warnings to mobilise, I think you will see exactly what is meant by those scientists saying the Indian Ocean is too small for a warning system to be of much use (there again, you probably will not so I won't persevere).

John