Tsunami Warnings

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#1691967 18-Dec-2016 23:29

frankv:
blakamin:

But anything over a 6 in the pacific region pretty much "automatically" gets a tsunami warning from civil defence... WHY?

Because it's new science. Remember that before the Indian Ocean tsunami, there was *no* warning system anywhere. People hardly even knew the word.

So they've built a new system which generates warnings where there is some threshold probability of an actual tsunami. Someone has fairly arbitrarily decided what level of risk should generate a warning. And, naturally, they've erred on the side of caution. As time goes by and the risk factors are better understood, and more and better instrumentation is put into place, the quality of the data will improve, and so will the reliability of warnings.

Exactly. There was an interesting interview on radio nz about exactly this topic recently. Can't find it again sorry. Anyway, long story short it requires a fair bit of analysis to be accurate about tsunami. We dont have that capability on tap in our current system.

USA for instance has multiple teams around their continent and around the clock and when an event occurs they can assemble a multidisciplinary team of teams and perform an analysis fairly quickly and get a result.

NZ system is something like
1. all events over x size issue a warning
2. wake up one person to have a look at it and perform a quick assessment.
3. If it is looking a bit serious, wake up a couple more people to add their expertise
4. no issues? withdraw the warning.

That was my takeaway from the 10 minute item, it's worth a listen if you can find it. It didn't have my full attention but almost exactly the same questions raised in this topic raised by the interviewer as I recall.

Edit: found it:

http://www.radionz.co.nz/national/programmes/saturday/audio/201826327/kevin-furlong

"Kevin Furlong is Professor of Geoscience at Penn State university and an authority on tsunami alert monitoring. Part of his work includes understanding the many methods of monitoring employed in earthquake prone areas and countries around the world,"

^podcast format pop it in the car for tomorrow. well worth a listen. (23 minutes)^

k1wi

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#1693044 21-Dec-2016 04:07

Not a geoscientist, but I wouldn't mind a graduated response - tsunami watch (be alert, avoid beaches etc), upgraded to a tsunami warning (evacuate) if necessary.

dickytim

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#1693046 21-Dec-2016 06:19

I know someone who worked for civil defence in BOP, I was talking to him about it. The problem is, If they crunch all the data etc. it takes an hour or so to get an accurate idea, by that time any close tsunami is already on us. If they issue a warning every time there is also the risk that people become complacent. They are looking at implementing a better system, and the advise has always been that a quake over a certain magnitude go to higher ground until a you hear it is safe.

blakamin, the answer is actually Y E S there has been quite a few that have hit NZ, they have been quite small for the most part, 30cm high etc. but yes they have regularly hit.

MikeB4

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#1693053 21-Dec-2016 07:34

In my life time I have experienced maybe a dozen warnings and only ONCE had the sirens go off. I do not believe that is too often.

I wonder how long a subject thread would be here if a tsunami struck and EMO had not issued warnings. These alerts and warnings are to try and save lives not annoy people.

Pumpedd

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#1693066 21-Dec-2016 08:23

MikeB4: In my life time I have experienced maybe a dozen warnings and only ONCE had the sirens go off. I do not believe that is too often.

I wonder how long a subject thread would be here if a tsunami struck and EMO had not issued warnings. These alerts and warnings are to try and save lives not annoy people.

I still want to know what we are supposed to do when we do get a warning???

Gridlock will happen within a few minutes, so whats the point?..and where do people think they will drive to??...it will be utter mayhem and confusion.

Fred99

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#1693071 21-Dec-2016 08:44

I've heard them go off (in anger) only once - on 14 November, when they were started at about 2AM.

The earthquake was at 12:02am. The first waves had already long arrived before the alarms were activated.
There was a tsunami threat. The waves with ~2m height had been showing on the Kaikoura gauge shortly after the quake.
The view from my window showed people were trying to evacuate at risk areas, but apart from the warning being a couple of hours late, the roads were gridlocked.

If there had been a serious tsunami in Chch, then people would not have been able to be evacuated in time. Not even close.

PaulBags

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#1693074 21-Dec-2016 09:02

The the sirens started as we were evacuating, about 2:10AM before they started, and roads were already full/gridlocked. There were police about with sirens, but none directing traffic at round abouts and with one round about with traffic from two directions one direction was perpetually giving way - madness.

Anyway I'd read the warning/alert an hour earlier on social media (note I did not hear it on the radio, radio nz our offical national station, which I was listening to). There's been so many false alarms it took that hour to convince my parents to evacuate - and I don't know what'll happen next time since nothing happened :/.

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Talkiet

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#1693086 21-Dec-2016 09:18

MikeB4: In my life time I have experienced maybe a dozen warnings and only ONCE had the sirens go off. I do not believe that is too often.

I wonder how long a subject thread would be here if a tsunami struck and EMO had not issued warnings. These alerts and warnings are to try and save lives not annoy people.

You're missing my point.

My point is that by the warnings and alerts being consistently overstated people will stop paying attention to them and when there is a REALLY serious threat we may not react with the appropriate urgency because we've been trained into believing that the alerts and warnings not being serious.

You literally (thinks for a second about the word...) couldn't find a better real world analogy for crying wolf unless you were living in an area with wolves and had small children playing outside and pranked them regularly by shouting "WOLF!" when there in fact was not a wolf in sight.

It's all well and good to say "Well people should just pay attention to them and react to all of them as if they were real" but here's the problem.

I promise you, it's going to be harder to change group human behaviour, especially in response to temporally sparse stimuli, compared to doing a better job of issuing more appropriate warnings.

It's like the scientists that do the numbers have never spoken to any social scientists or behaviourists.

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

dickytim

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#1693092 21-Dec-2016 09:36

So we don't want the warnings until the data is crunched, but by the time the data is available the tsunami has been and gone?

On the other hand we don't want preventative warnings unless the data suggests there is a real danger coming.

This is the rock and the hard place.

MikeB4

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#1693099 21-Dec-2016 09:53

Pumpedd:

MikeB4: In my life time I have experienced maybe a dozen warnings and only ONCE had the sirens go off. I do not believe that is too often.

I wonder how long a subject thread would be here if a tsunami struck and EMO had not issued warnings. These alerts and warnings are to try and save lives not annoy people.

I still want to know what we are supposed to do when we do get a warning???

Gridlock will happen within a few minutes, so whats the point?..and where do people think they will drive to??...it will be utter mayhem and confusion.

Visit the Get Thru site or GNS they have valuable information as to what you should do.

MikeB4

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#1693100 21-Dec-2016 09:54

Talkiet:

MikeB4: In my life time I have experienced maybe a dozen warnings and only ONCE had the sirens go off. I do not believe that is too often.

I wonder how long a subject thread would be here if a tsunami struck and EMO had not issued warnings. These alerts and warnings are to try and save lives not annoy people.

You're missing my point.

My point is that by the warnings and alerts being consistently overstated people will stop paying attention to them and when there is a REALLY serious threat we may not react with the appropriate urgency because we've been trained into believing that the alerts and warnings not being serious.

You literally (thinks for a second about the word...) couldn't find a better real world analogy for crying wolf unless you were living in an area with wolves and had small children playing outside and pranked them regularly by shouting "WOLF!" when there in fact was not a wolf in sight.

It's all well and good to say "Well people should just pay attention to them and react to all of them as if they were real" but here's the problem.

I promise you, it's going to be harder to change group human behaviour, especially in response to temporally sparse stimuli, compared to doing a better job of issuing more appropriate warnings.

It's like the scientists that do the numbers have never spoken to any social scientists or behaviourists.

Cheers - N

There is a big difference between not getting a point and not agreeing with a point.

PaulBags

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#1693112 21-Dec-2016 09:57

The assumption here is that it can be predicted more accurately and that it's the warnings that need to change. More accurate prediction to eliminate warnings of unlikely events would be great, but what do we do in the mean time? If 1000 events are, by our current understanding, exactly as likely as each other to lead to loss of life but only one does - what do you do if you can't narrow it down? Remember never warning means people will die, you just don't know which time.

People are happy with much longer odds on lotto, I don't think we should be taking them with our lives.

Pumpedd

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#1693125 21-Dec-2016 10:20

Isnt there a Pacific Tsunami warning centre based in Hawaii that issues most if not all warnings?

frankv

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#1693211 21-Dec-2016 12:50

dickytim: So we don't want the warnings until the data is crunched, but by the time the data is available the tsunami has been and gone?

On the other hand we don't want preventative warnings unless the data suggests there is a real danger coming.

This is the rock and the hard place.

Personally, I don't believe the story of it taking an hour to crunch the numbers. With modern computers and well-designed software (especially multi-threaded), there's very little analysis that will take an hour. I suspect the number-crunching story is a convenient myth, and that the actual time is spent on getting people to verify the results and decide what to do with it.

MikeB4

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#1693214 21-Dec-2016 12:56

frankv:

dickytim: So we don't want the warnings until the data is crunched, but by the time the data is available the tsunami has been and gone?

On the other hand we don't want preventative warnings unless the data suggests there is a real danger coming.

This is the rock and the hard place.

Personally, I don't believe the story of it taking an hour to crunch the numbers. With modern computers and well-designed software (especially multi-threaded), there's very little analysis that will take an hour. I suspect the number-crunching story is a convenient myth, and that the actual time is spent on getting people to verify the results and decide what to do with it.

My brother in law is an engineer working in the field and he confirms the time and complexity

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