NZ, a nice place to visit but... (10 Apr, 2017)

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NZ, a nice place to visit but... (10 Apr, 2017)

Postby aardvark_admin » Mon Apr 10, 2017 8:37 am

This column is archived at: http://aardvark.co.nz/daily/2017/0410.shtml

How long before NZ becomes the disaster tourism capital of the world?

Surely, if we continue enduring natural disasters at the scale and frequency of recent quakes and floods, insurance companies will give us a wide berth and we'll become a nice place to visit -- but nobody will want to stay here.

Are we doing enough to prepare for the proven dramatic effects that climate change is having on rainfall patterns?

Are we prepared for the next big quake which could cause even more damage to infrastructure and population centres?

Or will we remain "reactive" rather than "proactive" when it comes to such things?

Yeah, let's leave it for the next government shall we?

She'll be right mate!

Or will it?
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby GSVNoFixedAbode » Mon Apr 10, 2017 9:54 am

I remember years ago reading about climate change and the author referring to a "Climate Cliff" - I wonder if we're just on that edge now.
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby phill » Mon Apr 10, 2017 10:06 am

in a relatively short period of time my insurance for house only has gone from ~$150 - ~ $700
hence i pick and choose the times i am insured .. and if i could get house insurance for less than a year ( like a month )
it would be even shorter ... i have no risk from flood ( hilly mount on sandy base ) and almost none from earthquake or tsunami ( far north height 60 meters )
so its cyclones only .. when they form on track for nz i get insurance .. other than that i have none
why do i do this
same risk assessment insurance companies should use but haven't .. 1 of the reasons i bought this particular place is because its safe ( er ) from disasters than most of nz
edgecombe was a disaster waiting to happen .. since it is on a flood plain that dropped 1.5 meters in march 1987 .. the we will rebuild bullshit instead of the logical time to move everything out of here ( christchurch / wallytown take note ) ... the original city planners were allowed to be wrong in some of the places they first built .. but you have to be a special form of dickhead to keep compounding it by pretending it wont happen again and again and yet still be surprised each time
some simple rules to think about
dont build a settlement on a flood plain or anywhere with restricted drainage
dont build multistory buildings in an earthquake zone ( hence no cities )
dont put major assets in an active volcanic field
now we can add
start building cyclone compliant dwellings
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby SeeNoEvil » Mon Apr 10, 2017 10:23 am

I live a little way south of Taumarunui and yesterday morning I received an email from a family member in Auckland asking if I'd felt "the earthquake". I had no idea what she was talking about but checked out geonet and found the following:

http://www.geonet.org.nz/quakes/region/ ... 017p263661

This was supposedly centred about 40 south-west of Taumarunui, and very deep. Yet if you look at the felt reports, they are all clustered much further south, including some "extreme" in Palmerston North, and plenty of "strong" further south. I replied to my sister saying it seemed to me that geonet had probably miscalculated the location of this particular quake. Seems more likely (to me at least) that it came from far further south and so might also be linked in some way with the group late last night.

Any geologists here that can put me straight?
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby Logan Savage » Mon Apr 10, 2017 11:26 am

aardvark_admin wrote:When we're at rest on the surface of the earth, we experience an acceleration of 1G
Sorry I don't agree. Acceleration is the rate of change of velocity per unit of time. A free-falling object will accelerate at about 9.78 m/s/s at the equator and about 9.83 m/s/s at the poles, which is called gravitational acceleration. Conversely an object at rest on the surface of the earth is, as you say, at rest. Its velocity is not changing so it is not undergoing acceleration. Instead the object at rest on the ground is subject to a normal force exerted by the ground, and that leads to apparent weight.

Now the so called 'g' forces experienced by eg an aircraft are misnamed. It would be better called the Load Factor which is equal to Lift/Weight where a load factor of 1 indicate lift and weight are identical and results in level flight. Since this is a ratio of 2 forces it is actually dimensionless. The casual use of g eg "a 3G acceleration" is because it feels similar to 3 times the apparent weight of the observer. Its a handy guide, but in physical terms Load Factor is not the same as acceleration of gravity.
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby Screw » Mon Apr 10, 2017 1:20 pm

Agreed Logan. Acceleration is an action of a body in motion not a body at rest. Makes a mockery of the biblical account of Joshua's' Earth standing still story. Josh and his lads were supposedly near the equator, so if the earth suddenly stopped spinning everyone on the surface would travel westwards at 1000Mph. Nasty if there is something in their way! :shock: Splat!! Then when the big fella started it a-spinning again, the opposite would happen. Story is Taurus Excretus!

We need to be aware that with CC we will get more massive storms as the climate balances itself out again.

Sad that John Clarke (Fred Dagg) has shuffled off too.
Last edited by Screw on Mon Apr 10, 2017 1:22 pm, edited 1 time in total.
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby SeeNoEvil » Mon Apr 10, 2017 1:21 pm

My rough calculations (and checking of timing against youtube videos of airliners accelerating, rotating, and climbing out) indicate average horizontal acceleration before starting to rotate is something in the order of 2 m/s/s, and average vertical acceleration from start of rotate to established climb is around 1.5 m/s/s. The latter is based on climbing out at 10 degrees relative to level, and taking about 10 seconds to get to that angle from start of rotate, and a speed of about 300 kph.
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby Perry » Mon Apr 10, 2017 1:33 pm

Bruce wrote:We've had a succession of really strong earthquakes which have stretched the insurance industry to breaking point. How long before the quakes and floods push insurance premiums even higher than they already are and make housing even less affordable for young Kiwis?

Doesn't this border on that most popular of topics right now: fake news?

You think that was fake news! How about this fake insurance news item, from last week. (Proof readers are not a dying breed - they're extinct!) Or maybe NZ young male drivers should emigrate?

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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby Kiwiiano » Mon Apr 10, 2017 9:04 pm

First thought re aircraft takeoff: passengers experience 1G vertically and XG horizontally. Re the acceleration with the Waiau seismograph, the reporter may be getting confused by the logarithmic scale of earthquake energies??
Re learning to live with disaster....welcome to the new normal. What we are seeing has been predicted since the 1800's (Note the one of the first scientists to raise a warning flag was Fourier, who was scientific advisor to Napolean Bonaparte, so we can hardly claim it's all a big surprise.) More energy trapped in the atmosphere means that evaporation is faster (provoking droughts) leading to more water in the atmosphere (heavier rainfall and more floods). Meanwhile, particularly in the northern hemisphere, the Arctic amplification is pushing temperatures 30°F above normal, reducing the thermal gradient southward, which is causing the circumpolar jet streams to slow and form bigger loops that precess even slower than usual hence weird weather lingers longer.
We're seeing slightly different effects here in the Southern Hemisphere but unusual rainfall is clearly increasing.
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Re: NZ, a nice place to visit but... (10 Apr, 2017)

Postby SeeNoEvil » Tue Apr 11, 2017 1:04 am

Kiwiiano wrote:First thought re aircraft takeoff: passengers experience 1G vertically and XG horizontally. Re the acceleration with the Waiau seismograph, the reporter may be getting confused by the logarithmic scale of earthquake energies??


I feel we are getting into that 3% where you aren't right Kiwiano! I don't think logarithmic scales have anything to do with this particular issue. :)

The article is pretty consistently in using acceleration for starters, except for the paragraph Bruce already highlighted where it says:

"Readings taken at the North Canterbury town of Waiau during the November event proved a new record for vertical ground acceleration, reaching 3g, or 30 times the force an airliner passenger feels at take-off."

If it had said "vertical acceleration" instead of "force" then it would have been okay.

Have a look at the diagrams from this geonet article: http://info.geonet.org.nz/display/quake ... Earthquake

Notice that many of the vertical accelerations are shown as less than 1g. This is because they are using 1g to represent the acceleration due to gravity at the earth's surface if you were also in freefall - in other words 1g is talking about an acceleration of just under 10 m/s/s.

Gravity is exerting a downwards force on your body as you accelerate down the runway, and that force is about 9.8 Newtons per kg of mass. We feel and generally refer to this as "weight", as there is usually also the ground or similar creating an equal and opposite force. In this case you have essentially zero vertical acceleration. But when the aircraft rotates and its velocity vector changes direction from parallel to the ground to some reasonable angle up, up and away, then you also accelerate (even if your speed might stay the same). This brief period of vertical acceleration will make you feel a little heavier, and is roughly what I calculated earlier. Presumably this small vertical acceleration is what the reporter was also trying to compare with the approximate 3g vertical acceleration measured at some points during the quake.

So, saying the earthquake's vertical acceleration was about 30 times the vertical acceleration experienced by passengers leaving the runway during take-off in an airliner would have been acceptable in my book, although perhaps also not a very "useful" way of comparing things. The feeling of weight for a person during take-off (more precisely as the aircraft rotates nose up and starts to climb away from the ground) will briefly be a little higher than when trundling along the runway, but it's not a huge change, or for very long.

The upward force from the floor and the seat on their body will be around 1.1 or 1.2 times what it was just before take off, with the extra coming from the effect of the vertical acceleration. Gravity is still pulling them towards the centre of the earth but now we also have the aircraft accelerating upwards over a few seconds. Your felt weight will increase a little as a result, but this is still only a little more than a third of what their apparent weight would have been if they were at the spot during the earthquake where the 3g vertical acceleration is supposed to have happened.

In other words, for most people a more useful and accurate statement would have been that your body would have felt about three times it's usual weight if you were standing at the spot where the ground underwent maximum vertical acceleration during the earthquake.

You'd also experience that "3g" feeling of tripled weight if you were in an aircraft executing a tight level orbit with an a bank angle of about 65 to 70 degrees.

Phew! :oops:
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