Hikurangi Subduction zone

Forums › Off topic › Hikurangi Subduction zone

1 | 2

MikeAqua

7616 posts

Uber Geek

#1968886 6-Mar-2018 13:41

frankv:

Wellington CBD and Hutt Valley is a special case, being situated on a harbour with a narrow entrance. The rate at which the water level in the harbour will rise will be limited by how fast water can get in through the harbour entrance. My wild-ass guess would that you would have more than 15 minutes after Seatoun was inundated before the CBD was endangered.

That is somewhat heartening. 15 minutes should be enough.

Mike

Pluralsight

Learn cloud, mobile, security, data and web technologies with Pluralsight (affiliate link).

wellygary

7380 posts

Uber Geek

#1968933 6-Mar-2018 14:19

tdgeek:

Interesting piece, a potential 9.0 with a tsunami that is the real danger

https://www.stuff.co.nz/national/nz-earthquake/101989915/megathurst-quake-could-bring-12mhigh-waves-to-nzs-east-coast

You have gotta love Stuff, a quick google shows that the ran a similar story twice in the last 6 months.

November 2017

https://www.stuff.co.nz/national/98878426/when-hikurangi-subduction-zone-megathrust-triggers-tsunami-think-japan-2011

October 2017

https://www.stuff.co.nz/national/nz-earthquake/97652592/hidden-megathrust-fault-could-hammer-new-zealand-with-84-quake

tdgeek

28601 posts

Uber Geek

Trusted

Lifetime subscriber

#1968957 6-Mar-2018 14:37

wellygary:

tdgeek:

Interesting piece, a potential 9.0 with a tsunami that is the real danger

https://www.stuff.co.nz/national/nz-earthquake/101989915/megathurst-quake-could-bring-12mhigh-waves-to-nzs-east-coast

You have gotta love Stuff, a quick google shows that the ran a similar story twice in the last 6 months.

November 2017

https://www.stuff.co.nz/national/98878426/when-hikurangi-subduction-zone-megathrust-triggers-tsunami-think-japan-2011

October 2017

https://www.stuff.co.nz/national/nz-earthquake/97652592/hidden-megathrust-fault-could-hammer-new-zealand-with-84-quake

Yep! When I googled for more info, I saw Herald ran a few too

They could do a Netflix and have "Stuff Originals", would save time for us consumers each and every day, Stuff webpagelet

MaxLV

656 posts

Ultimate Geek

#1970015 6-Mar-2018 16:31

Fred99:

Here you go:

Paleotsunami database map

As well as the Hikurangi, there's also the Kermadec Trench.

There's also some scary Paleotsunami evidence with large run up on the SE coast of Australia. Problem with all this is that unless there's some other evidence dating an event (ie quake) that might have been responsible, there's no way of knowing where or what the event was that set off the tsunami - local or distant quake, volcanic, or even asteroid strike etc.

There's this history...

Evidence of multiple quakes, tsunami at ancient NZ settlement

The authors said there had been at least four earthquakes at the bar large enough to have changed the landscape – transforming the site from an island to part of a boulder bank – as well as the surrounding area.

The site had also been ravaged by three tsunamis – including one 1855 event that was large enough to have knocked down several buildings, stranded fish and lowered the land and nearby lagoons by one to two metres.

https://www.odt.co.nz/news/national/evidence-multiple-quakes-tsunami-ancient-nz-settlement

MaxLV

656 posts

Ultimate Geek

#1970019 6-Mar-2018 16:45

frankv:

MikeAqua:

This an interesting one for us. We are in a 10th floor apartment in Welly, on the flat a couple of blocks from the harbour.

I tried it one day walking down all the stairs and up the street to a safe height and it took me just over 10 minutes. In a real evacuation with stair and street congestion I think it would take a little over 15 minutes to exit the building and get to a safe elevation. I know that exiting our 7th floor office in a fire drills takes about 5 minutes.

That puts me in a real dilemma. A tsunami could arrive during that time and catch us on the flat.

Assuming the building is still intact: Should I stay or go?

Bear in mind that the predicitions are for earthquakes centred somewhere between Cape Turnagain and East Cape... lots of Wairarapa coast would be flooded long before the tsunami reached Wellington.

As well, Wellington CBD and Hutt Valley is a special case, being situated on a harbour with a narrow entrance. The rate at which the water level in the harbour will rise will be limited by how fast water can get in through the harbour entrance. My wild-ass guess would that you would have more than 15 minutes after Seatoun was inundated before the CBD was endangered.

It's not just earthquakes that could cause a Tsunami in the Wellington region:

Landslides in deep canyons in Cook Strait can set off 10-metre high tsunamis

Landslides in offshore canyons could cause tsunamis more than 10 metres high along parts of the Cook Strait coastline, scientists have calculated.

Niwa and GNS Science researchers spent four years assessing the risk of tsunamis generated by landslides in the Cook Strait Canyon.

It was estimated a 1m landslide-generated tsunami could be expected somewhere along the greater Cook Strait coastline every 140 years, Niwa hydrodynamics scientist Dr Emily Lane said.

https://www.stuff.co.nz/national/72778250/landslides-in-deep-canyons-in-cook-strait-can-set-off-10metre-high-tsunamis

MaxLV

656 posts

Ultimate Geek

#1970021 6-Mar-2018 16:49

Interesting...

There are suggestions a very large tsunami in the past 7000 years carried whales to an elevation of around 35m on Wellington's Miramar Peninsula. The theory is based on early 20th century reports of whale skeletons being found preserved in sand in the area.

https://www.stuff.co.nz/national/72778250/landslides-in-deep-canyons-in-cook-strait-can-set-off-10metre-high-tsunamis

alasta

6232 posts

Uber Geek

Trusted

Subscriber

#1970155 6-Mar-2018 20:38

I wonder what would happen to the Cook Strait ferries in a major tsunami. I guess you'd be buggered if you're on one.

frankv

5582 posts

Uber Geek

Lifetime subscriber

#1970158 6-Mar-2018 20:46

MaxLV:

It's not just earthquakes that could cause a Tsunami in the Wellington region:

Landslides in deep canyons in Cook Strait can set off 10-metre high tsunamis

Right. But in a geologically unstable area, what is most likely to trigger an underwater landslide? An earthquake. And surely an entirely underwater landslide will mostly be a local place-swap between some dirt/rocks and some water? There won't be a really big wave generated like a massive uplift of the ocean floor.

Incidentally, my variant on Betteridge's Rule.... The word "could" in a headline is a synonym for "probably won't".

frankv

5582 posts

Uber Geek

Lifetime subscriber

#1970163 6-Mar-2018 20:53

alasta:

I wonder what would happen to the Cook Strait ferries in a major tsunami. I guess you'd be buggered if you're on one.

Probably depends where it was at the time... in the mouth of Wellington Harbour or Tory Channel, I'd say you'd be in deep strife. Further out in deep water, not so much.

ResponseMediaNZ

518 posts

Ultimate Geek

ID Verified

Trusted

Subscriber

#1970169 6-Mar-2018 21:10

tdgeek:

wellygary:

tdgeek:

Interesting piece, a potential 9.0 with a tsunami that is the real danger

https://www.stuff.co.nz/national/nz-earthquake/101989915/megathurst-quake-could-bring-12mhigh-waves-to-nzs-east-coast

You have gotta love Stuff, a quick google shows that the ran a similar story twice in the last 6 months.

November 2017

https://www.stuff.co.nz/national/98878426/when-hikurangi-subduction-zone-megathrust-triggers-tsunami-think-japan-2011

October 2017

https://www.stuff.co.nz/national/nz-earthquake/97652592/hidden-megathrust-fault-could-hammer-new-zealand-with-84-quake

Yep! When I googled for more info, I saw Herald ran a few too

They could do a Netflix and have "Stuff Originals", would save time for us consumers each and every day, Stuff webpagelet

Yip its not new to Emergency Managers... Nor is the modeling. Yes its been refreshed but that's just because as we all know technology evolves and so does science and how we look at Tsunami's

We live in one of the most Hazardous places on earth when it comes to disasters so we just need to start being more prepared.. I bet the majority on here would be more parepared for a technology failure than they would be for the next natural disaster...

BlinkyBill

1443 posts

Uber Geek
Inactive user

#1970276 7-Mar-2018 03:41

Wellington will be fine - the council painted some blue lines on the roads.

MikeAqua

7616 posts

Uber Geek

#1971097 8-Mar-2018 10:48

So it turns out that our apartment building in Welly is only about a block from the blue lines (according to the tsunami zone map). The blue lines are the supposed start of the safe zone in the event of a WCS Tsunami from a 9.0 quake on the Hikurangi fault.

I've never actually noticed the blue lines so I'll have to go for a wander and check it out.

Mike

1 | 2