CD tsunami warning 30 July

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#3398696 31-Jul-2025 13:10

One of my phones gave me another one at about 9:30 when I had just got off the motorway on the way to work. Wonder if there was a spike in crashes at 6:30 when the needless one went out.

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#3398697 31-Jul-2025 13:14

Looking at Android settings, there are three tiers, emergency alerts , extreme threats , and severe threats.

Given the actual threat to loss of life or injury was low in this specific event, I can't see how CD flow charts for risk management lead them to issue an emergency notification, particularly as a 6.30am alert.

Yes there have been really bad tsunamis before but the science had shown this was not a problem. We had several countries get hit first and all coped fine with minimal impact.

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Mrcutiepatootie

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#3398703 31-Jul-2025 13:23

Getting a lot of responses from my comment so just to clarify my point was more about how alerts are being used especially when the morning alert didn’t add anything new to what was already sent the night before.It feels like over-alerting when the situation hasn’t changed.

MikeAqua

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#3398737 31-Jul-2025 15:16

Are CD able to be a bit more selective where they send the alert. I'm currently about 50m above sea level so I didnt really need to be woken up at 6:30am.

Mike

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#3398739 31-Jul-2025 15:19

Senecio:

As an interesting aside. This is the first emergency notification that has actually over ridden my phone’s silent setting and made a noise. My phone is always on silent and previous notifications have come through without any noise.

Ditto.

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MikeAqua

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#3398742 31-Jul-2025 15:25

xpd:

(Very basic level) Fill your bath with water. Drop a stone in it close to one side. Ripple effect. Just because where you dropped the stone is on the other side of the bath does not mean any part of your bath avoids the ripple.

I'm happy to know that "ripple" could be on its way, rather than have no notification and be out on a boat and have it come along, causing the boat to flip....

I think the scales are a little out of whack in your analogy. The Pacific Ocean is vast, and we're at the opposite end from Russia. Waves reduce in amplitude as they propagate out from a disturbance point. That's because all the energy is being distributed across a lengthening wave front.. With enough distance, they dissipate altogether. A more accurate example would be something like: Throwing a jaffa (a giant jaffa if you're feeling bougie) in one end of a 25m swimming pool and seeing what the ripples are like at the other end.

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#3398745 31-Jul-2025 15:30

I am curious how they select the target area. I can see two possibilities. One is they select the specific cell towers. This I consider highly unlikely with 6000+ towers across all the four networks (if you count RCG separately). Another possibility is they select by LAC/TAC area which the telcos use to group around 50-100+ towers. I suspect it may be some variant of this as this number is more manageable. In some parts of the country LAC/TAC areas are quite large and so I can see why some areas may get alerts that's not very relevant just because they happen to fall into the same LAC/TAC as a high risk area. Stewart Island for example falls into the same LAC/TAC as most/all of Southland so any alerts affecting one or the other may go to all of the towers in that LAC/TAC. Or maybe they do have some way for specific towers to be chosen. I also wonder who decides this -- does NEMA tell the telcos the general area they want and the telcos do the rest to the best of their understanding or is it something NEMA et al has some finegrated control over and telcos just carry out their instructions?

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thermonuclear

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#3398757 31-Jul-2025 16:02

MikeAqua:

A more accurate example would be something like: Throwing a jaffa (a giant jaffa if you're feeling bougie) in one end of a 25m swimming pool and seeing what the ripples are like at the other end.

Crikey! If only RJ's had known about this wave experiment we might have saved the round orange confectionary treat!

fearandloathing

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#3398813 31-Jul-2025 16:29

KiwiSurfer:

I am curious how they select the target area. I can see two possibilities. One is they select the specific cell towers. This I consider highly unlikely with 6000+ towers across all the four networks (if you count RCG separately). Another possibility is they select by LAC/TAC area which the telcos use to group around 50-100+ towers. I suspect it may be some variant of this as this number is more manageable. In some parts of the country LAC/TAC areas are quite large and so I can see why some areas may get alerts that's not very relevant just because they happen to fall into the same LAC/TAC as a high risk area. Stewart Island for example falls into the same LAC/TAC as most/all of Southland so any alerts affecting one or the other may go to all of the towers in that LAC/TAC. Or maybe they do have some way for specific towers to be chosen. I also wonder who decides this -- does NEMA tell the telcos the general area they want and the telcos do the rest to the best of their understanding or is it something NEMA et al has some finegrated control over and telcos just carry out their instructions?

your answer was here:

https://www.tvnz.co.nz/shows/seven-sharp/clips/the-great-emergency-alert-test

the episode does not seem to be available now. Maybe someone else has a link.

Aucklandjafa

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#3398859 31-Jul-2025 17:44

KiwiSurfer:

I am curious how they select the target area. I can see two possibilities. One is they select the specific cell towers. This I consider highly unlikely with 6000+ towers across all the four networks (if you count RCG separately). Another possibility is they select by LAC/TAC area which the telcos use to group around 50-100+ towers. I suspect it may be some variant of this as this number is more manageable. In some parts of the country LAC/TAC areas are quite large and so I can see why some areas may get alerts that's not very relevant just because they happen to fall into the same LAC/TAC as a high risk area. Stewart Island for example falls into the same LAC/TAC as most/all of Southland so any alerts affecting one or the other may go to all of the towers in that LAC/TAC. Or maybe they do have some way for specific towers to be chosen. I also wonder who decides this -- does NEMA tell the telcos the general area they want and the telcos do the rest to the best of their understanding or is it something NEMA et al has some finegrated control over and telcos just carry out their instructions?

pretty sure they can zone down to sectors. Ie, industrial fires in Auckland’s suburbs. Martinborough also had an alert for months when they had the E.Coli outbreak - the alert would only come through when you got to the outskirts of the town.

They must know every site/sector, and if said site/sector falls within the area they want to alert - then alerts only go to those respective sites.

mentalinc

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#3398860 31-Jul-2025 17:45

Seems this is the guidance document CD should have been following: https://www.civildefence.govt.nz/assets/Uploads/documents/publications/guidelines/directors-guidelines/DGL-21-18-Assessment-and-Planning-for-Tsunami-Vertical-Evacuation.pdf

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Aucklandjafa

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#3398861 31-Jul-2025 17:45

MikeAqua:

Are CD able to be a bit more selective where they send the alert. I'm currently about 50m above sea level so I didnt really need to be woken up at 6:30am.

Yeah, this is only a recent addition. Whilst absolutely punishing, if it’s gonna save a life then I guess it’s a good thing??

DS248

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#3398865 31-Jul-2025 18:01

Gurezaemon:

Mrcutiepatootie:

I get that it’s an emergency and I’d appreciate if I lived in Japan or close to where it happened, but they’ve sent out these alerts as if the tsunami’s going across the pacific to get here. More of a nuisance than an emergency if anything.

The 1960 Valdivia earthquake in Chile killed 138 people in Japan, 61 in Hawaii, and 32 in the Philippines.

Distance from an earthquake is no guarantee of safety from a tsunami.

...

Correct, but comparison with the 1960 Chile earthquake is a bit misleading. The 1960 Chile earthquake (M9.5) was an order of magnitude larger than the recent Kamchatka event (M8.8) in terms of energy and seismic moment. Hugely different, as illustrated in the tsunami simulations below for the 1960 (M9.5) and 2010 (M8.8) earthquakes (images ex NOAA, https://www.noaa.gov/jetstream/tsunamis/tsunami-propagation)

kiwifidget

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#3398870 31-Jul-2025 18:10

I'm not sure I got the alerts.

How do I check?

Samsung S20.

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DS248

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#3398871 31-Jul-2025 18:11

Re those images, also note that for these types of events, directionality is also very relevant, not just distance from the fault source. That is due to the orientation of the fault source, the fact that the faults are hundreds of km long (not point sources = jaffa!), the curvature of the earth, and other factors

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