NZ earthquake 14.11.16 - Mag 7.8

[fresh_42]

I know we have members who watch earthquakes and especially in that region.

http://www.bbc.com/news/world-asia-37967178
Potsdam and CNN even report 7.8 in 10 km depth. Tsunami warning set.
Does anybody know more?

 

[Borg]

Here's the USGS info:
http://earthquake.usgs.gov/earthquakes/eventpage/us1000778i#executive

They are also reporting 7.8.

 

[Borg]

Sure the link has been meant?

Oops. Fixed it.

 

[StevieTNZ]

apologies for the sloppy writing

http://www.stuff.co.nz/national/86416304/live-north-canterbury-quake

"A severe earthquake measuring 7.5 magnitude has hit in North Canterbury, near Hanmer Springs.

It was widely felt in both the South and North Islands, as far north as Auckland, causing damage and knocking out power."

I felt it all the way in Wellington. The house shook so much I thought the earthquake was based in Wellington. A few things fell down. Also, lots of aftershocks, some rather big, some small but still noticeable.

Then the tsunami sirens went off so I had to get out of bed and gather a few items. Currently we are all further inland. I believe the sirens have now stopped, but we'll wait a bit more.

I cannot imagine the damage in Christchurch again.

 

[Bystander]

https://www.physicsforums.com/threads/7-4-earthquake-usgs-in-nz.893195/#post-5619024

Edit: @davenn

 

[Greg Bernhardt]

Hope everyone is safe!

 

[Borg]

A minor tsunami did occur in NZ but isn't expected to impact anything beyond the island.

RECOMMENDED ACTIONS
-------------------

* NEW ZEALAND CIVIL DEFENSE HAS ISSUED A TSUNAMI THREAT
MESSAGE FOR THE EAST COAST OF SOUTH ISLAND.

* TSUNAMI THREAT BEYOND NEW ZEALAND IS NOT EXPECTED.

TSUNAMI OBSERVATIONS
--------------------

* THE FOLLOWING ARE TSUNAMI WAVE OBSERVATIONS FROM COASTAL
AND/OR DEEP-OCEAN SEA LEVEL GAUGES AT THE INDICATED
LOCATIONS. THE MAXIMUM TSUNAMI HEIGHT IS MEASURED WITH
RESPECT TO THE NORMAL TIDE LEVEL.

GAUGE TIME OF MAXIMUM WAVE
COORDINATES MEASURE TSUNAMI PERIOD
GAUGE LOCATION LAT LON (UTC) HEIGHT (MIN)
-------------------------------------------------------------
CASTLEPOINT NZ 40.9S 176.2E 1210 0.12M/ 0.4FT 18
WELLINGTON NZ 41.3S 174.8E 1232 0.43M/ 1.4FT 16
KAIKOURA NZ 42.4S 173.7E 1140 1.47M/ 4.8FT 16

 

[fresh_42]

As to why there are varying figures on the scale (USGS changed from 7.4 to now 7.9, Potsdam had 7. 8 and I've heard 6.6 by local reports):
A geology professor on a news channel here said: "It's difficult to determine the exact magnitude because it lasted so long, more than 2 minutes." Aftershocks are still occurring, but the danger of a major tsunami is likely banned.

 

[Astronuc]

Here's the USGS info:
http://earthquake.usgs.gov/earthquakes/eventpage/us1000778i#executive

They are also reporting 7.8.

NZ Geonet reports Mag 7.5 at 15 km depth, 15 km north-east of Culverden, which is about 53 km NNE of Amberley
https://www.geonet.org.nz/quakes/region/newzealand/2016p858000

There are several large quakes toward Kaikoura reported by USGS.

Mag 6.5 - http://earthquake.usgs.gov/earthquakes/eventpage/us10007795#executive,
https://www.geonet.org.nz/quakes/region/newzealand/2016p858055

Mag 6.2 - http://earthquake.usgs.gov/earthquakes/eventpage/us100077aj#executive,
https://www.geonet.org.nz/quakes/region/newzealand/2016p858279

and a few more in the 5 to 6 Mag range.

 

[StevieTNZ]

It was so scary, I was nearly in tears while we drove inland thinking our home could be gone. You hear about this happening overseas, but you really know what it feels like when you're faced with that situation.

A lot of schools and business' will be closed in Wellington and Christchurch. The trouble is NCEA end of year exams are happening.
"NZQA are yet to issue a statement on exams but they have talked to RNZ. A spokeswoman said most schools around the country should be open for business, but others in the quake and tsunami zones may not be. It may be the case at some schools that their practice exam results are used in place of exams, using the standard "derived grades" process."

So far, two people are confirmed dead.

 

[CapnGranite]

Two nice videos on New Zealand tectonics


Pushing New Zealand's Boundaries

followed by:
New Zealand: where two tectonic plates collide

 

[davenn]

As to why there are varying figures on the scale (USGS changed from 7.4 to now 7.9, Potsdam had 7. 8 and I've heard 6.6 by local reports):
A geology professor on a news channel here said: "It's difficult to determine the exact magnitude because it lasted so long, more than 2 minutes." Aftershocks are still occurring, but the danger of a major tsunami is likely banned.

Yes, the initial report from GNS ( in NZ) was 6.6, it was horribly under estimated ... my system was in overload for some 40 minutes and when the USGS report of 7.5 came out I knew that would be much closer to reality.
The really interesting thing about this event and the subsequent ones is that they are very widespread but in a line from the original M7+ and trending NE'wards
The whole area fired up. I have seen this several times over the years around the world but not like this in New Zealand.
And interestingly, almost all of the larger following events were not even in the area of the main shock.

So far 2 people have been reported killed, one when their house collapsed on them Dave

 

[StevieTNZ]

And interestingly, almost all of the larger following events were not even in the area of the main shock.

Yeah! I was checking geonet.org.nz and I saw all these earthquakes after the 12.02am happening around the country... one even by Levin!

But you have scum like this -- http://www.stuff.co.nz/the-press/ne...ghton-family-has-house-ransacked-truck-stolen who take advantage of the situation. Low life scum bags.

 

[Evo]

So happy you and your family are ok Stevie.

 

[StevieTNZ]

So far 2 people have been reported killed, one when their house collapsed on them

http://www.stuff.co.nz/national/86431062/earthquake-the-elms-homestead-flattened-one-dead

Two people have been pulled alive from a home destroyed in the quake.

One person is understood to have died at the Elms homestead near Kaikoura Airport.

The two buildings on the property are piles of rubble, barely recognisable as buildings.

 

[CapnGranite]

I've been watching davenn's observation of the NE trend to the "aftershocks" and they are, indeed, unusual. Until the latest one, a 6.8 near the first quake, they (the later quakes) are moving closer to Wellington. It looks like they are along the offshore projections of the Wellington and Wairarapa faults on the other island. Very interesting and unnerving if I lived in Wellington.

 

[Astronuc]

I took a screen shot of the USGS page of recent earthquakes.

The Mag 7.8 is the blue dot, and the second Mag 6.5 is the red dot. North of Kaikoura, straddling the fault are a Mag 6.5, 6.2 and 6.1 earthquakes. To the northeast is a cluster of Mag 5s near Ward, NZ, Lake Grassmere and Cape Campbell.

Seismotectonics of the Eastern Margin of the Australia Plate
http://earthquake.usgs.gov/earthquakes/eventpage/us100077hw#region-info

 

[StevieTNZ]

This is interesting:

GeoNet says the massive 7.5 earthquake overnight seemed so long was because it was two quakes, not one - lasting a combined two minutes and triggering a swarm of frightening aftershocks.

EDIT: also, I think the largest aftershock so far has been 6.2 in the Nelson region. That hit at 1.34pm.
http://www.stuff.co.nz/nelson-mail/...learning-centres-closed-for-earthquake-checks

 

[davenn]

This is interesting:EDIT: also, I think the largest aftershock so far has been 6.2 in the Nelson region. That hit at 1.34pm.
http://www.stuff.co.nz/nelson-mail/...learning-centres-closed-for-earthquake-checks

ohhh man, you just got to love inaccurate media reporting . None of the events have been anywhere near Nelson City,
let alone Nelson Province

But the comment from GNS about it being a double event, is a possibility, it does happen periodically
I'm going to be really interested to see if any visual ground surveys of the region of the main event shows any surface faulting
It may not happen because of the depth.Dave

 

[Astronuc]

Another site for information and interesting maps showing faults.
http://www.canterburyquakelive.co.nz/

http://www.canterburyquakelive.co.nz/Browse/?Index=106
They have the big one at 7.53 Mag, or equivalent to 30 Mt.

Nelson to Kaikoura is about 130 km (80.7 miles). Is it possible Nelson received some P-waves? Possibly from the Mag 6+ group that were 12 to 23 km N to NNW from Kaikoura toward Blenheim?

A number of years ago, I was about 60 miles from a Mag 6.5, and I felt the P-wave then S-wave. I was sitting on a large couch, and all of a sudden, it started shaking like an imbalanced washing machine. Moments latter, it started bouncing.

 

[StevieTNZ]

This is an interesting video to watch, showing the earthquakes and where they occurred.
https://nz.news.yahoo.com/video/watch/33201729/watch-a-days-worth-of-earthquake-data-as-massive-7-5m-hits-new-zealand/#page1

 

[davenn]

Nelson to Kaikoura is about 130 km (80.7 miles). Is it possible Nelson received some P-waves? Possibly from the Mag 6+ group that were 12 to 23 km N to NNW from Kaikoura toward Blenheim?

ohhh yes, indeed the larger events the high 5's, 6's and the 7.5 would have all been felt in Nelson City area starting with the quick pulse of the P followed by the S and surface waves 10 - 15 sec later.

A number of years ago, I was about 60 miles from a Mag 6.5, and I felt the P-wave then S-wave. I was sitting on a large couch, and all of a sudden, it started shaking like an imbalanced washing machine. Moments latter, it started bouncing.

it's a freaky feeling huh.

 

[Astronuc]

Talk about ripping up the ground! 7.8 Magnitude Quake in New Zealand Leaves Cows Stranded on Small Island of Grass

https://www.yahoo.com/gma/video/7-8-magnitude-quake-zealand-084403999.html

 

[jtbell]

 

[StevieTNZ]

Yeah, saw that on the news. Poor animals. :(

Went to bed rather early last night, around 7pm. While I was trying to get asleep two aftershocks occurred. Both were located east of Wellington. The 2nd one was more violent than the first, and I thought that again things would fall down and the sirens would go off.

 

[StevieTNZ]

Somewhat of a sum up:
1. There have been more than 800 quakes since Monday's M7.5 quake in North Canterbury - which was two quakes together.
2. It's likely that smaller aftershocks will continue, but there is close to a 40% chance of another large shake soon.
3. Two people were killed in the quake, in Kaikoura and Mt Lyford.

and 4. Wellington is being hammered with heavy rain and winds. The Hutt River is, unconfirmed at the moment, "bursting its banks with all this rain."

 

[cosmik debris]

I woke just after midnight to my house falling apart again. There was slow rolling with no high frequency component which lasted for 2mins. It was different from the violent jolting of our Christchurch quakes of 5 years ago and I realized the quake was not local and some poor blighters were really in trouble. My first thought was that it was the Alpine fault as we expect this kind of quake from that fault. Luckily it was at night or casualties could have been a lot higher.

 

[StevieTNZ]

I woke just after midnight to my house falling apart again.

Where are you based?

 

[cosmik debris]

Where are you based?

I'm in Christchurch.

 

[StevieTNZ]

Did you feel the two just before?

http://www.geonet.org.nz/quakes/region/newzealand/2016p862338
then 42 seconds later, at a different location,
http://www.geonet.org.nz/quakes/region/newzealand/2016p862339

 

[cosmik debris]

Did you feel the two just before?

http://www.geonet.org.nz/quakes/region/newzealand/2016p862338
then 42 seconds later, at a different location,
http://www.geonet.org.nz/quakes/region/newzealand/2016p862339

No, we only felt the main shake plus one or two of the larger aftershocks. They all seem to propagate NE from the fault.

 

[StevieTNZ]

I woke just after midnight to my house falling apart again. There was slow rolling with no high frequency component which lasted for 2mins. It was different from the violent jolting of our Christchurch quakes of 5 years ago and I realized the quake was not local and some poor blighters were really in trouble. My first thought was that it was the Alpine fault as we expect this kind of quake from that fault. Luckily it was at night or casualties could have been a lot higher.

When I woke up because of the quake (I'm in Lower Hutt), I thought it would stop. But it got more intense and once I heard things falling down in other rooms, I thought 'this isn't good'. I expected that the quake was located quite near Wellington. It did go through my mind that the house could collapse, once I heard things falling. I -cannot- imagine what it was like down in Christchurch 2010 and 2011.

 

[StevieTNZ]

This is scary: http://www.stuff.co.nz/national/86497605/Concerns-over-building-stability-in-central-Wellington

Police have cordoned off an area of central Wellington over fears a large building is structurally unsafe.

Emergency Services rushed to Molesworth St, near Parliament, where the road has been blocked off.

And the building which houses staff for Statistics NZ is declared unsafe, and it may be a year before they could re-enter. Little detail has been shared about how it is inside, they believe some concrete beams have fallen.

 

[davenn]

My first thought was that it was the Alpine fault as we expect this kind of quake from that fault.

When the Alpine Fault unzips it will be a M8 + ... going on historical data that research unveiled about offset amounts etc ( remembering the last event was pre European settlement) It would be safe to estimate a M8.5 or so. Something in the order of ~ 10 times the amplitude of this latest event and there won't be anyone anywhere in NZ that won't feel it.

It's really interesting to note all the major events over the last 150 - 200 yrs have been have been to the south and north of the main central section of the AF.
I haven't seen any recent stress field data for the central section, it must be quite significant.

Dave

 

[Vanadium 50]

I was just shown a plot of the LHC beam excursion during the event. Of course the beam didn't shake - it was the reference point attached t the earth.

 

[CapnGranite]

Continent-scale strike-slip on a low-angle fault beneath New Zealand's Southern Alps: Implications for crustal thickening in oblique collision zones
http://onlinelibrary.wiley.com/doi/10.1002/2015GC005990/full

This site summarizes what's in the paper. Most of the research on the Alpine fault has been south of the area of the recent quakes, but this newish study might help explain the seemingly odd distribution of aftershocks.
http://blogs.agu.org/geospace/2015/...-for-rethinking-of-new-zealands-alpine-fault/

Of general interest:
http://www.victoria.ac.nz/news/2016/03/new-zealands-alpine-fault-biggest-mover-in-the-world

 

[CapnGranite]

Because of similarities to the San Andreas Fault, the Alpine Fault has been studied by geologists studying the SAF and the the larger transform system that it is part of. In the past week I've come to appreciate just how much more complicated the Alpine Fault is in relation to the plate boundaries compared to what's going on in California.

 

[cosmik debris]

When I woke up because of the quake (I'm in Lower Hutt), I thought it would stop. But it got more intense and once I heard things falling down in other rooms, I thought 'this isn't good'. I expected that the quake was located quite near Wellington. It did go through my mind that the house could collapse, once I heard things falling. I -cannot- imagine what it was like down in Christchurch 2010 and 2011.

It was pretty bad in 2010 - 11, the G forces, because the epecentre was almost directly below the city were very high which caused a lot of damage. The quakes were short but very violent. The lack of high frequency components this time were a good indicator that the quake wasn't local. I feel for you people because it is the months of aftershocks that wear you down, the lack of sleep makes the whole population irritable and in our case lasted for a good 18 months. You walk into a new building or room and immediately look for anything that could kill you. And then there is the insurance companies to deal with...

 

[cosmik debris]

This is scary: http://www.stuff.co.nz/national/86497605/Concerns-over-building-stability-in-central-Wellington
And the building which houses staff for Statistics NZ is declared unsafe, and it may be a year before they could re-enter. Little detail has been shared about how it is inside, they believe some concrete beams have fallen.

This is a very worrying state of affairs for a city that in many ways is more susceptible to a bad quake than many. I hope questions are asked. The deaths that occurred in Christchurch need not have happened if the buildings had been designed and built properly, and there is no reason why a relatively modern building should not be safe.

 

[StevieTNZ]

It appears that the earthquake on Monday at 12.02am has been upgraded from 7.5 to 7.8

"GNS Science has revised the magnitude of the large earthquake that struck at 12:02am on Monday from a 7.5 to a 7.8."

Live updates can be found here -- http://www.stuff.co.nz/national/86416304/live-north-canterbury-quake

 

[StevieTNZ]

@jtbell and all those concerned: the cows are now safe.

 

[davenn]

Yeah! I was checking geonet.org.nz and I saw all these earthquakes after the 12.02am happening around the country... one even by Levin!

GeoNet says the massive 7.5 earthquake overnight seemed so long was because it was two quakes, not one - lasting a combined two minutes and triggering a swarm of frightening aftershocks.

.

As I noted in an earlier comment this is a possibility, but it isn't the only cause of long duration shaking.
Once the chaos has died down a bit in the Seismo Obs at GNS, I would really like to query them on that statement and hopefully get a response as to why they think that?. I really think it may have been made in haste, considering at the time, they estimated a magnitude much smaller than what it really was. This meant the smaller size couldn't account for the shaking time that a larger event would have and they had to come up with a reason.

The other common cause is by the rupture mode. The 2 main ones are uni-lateral and bi-lateral. The significant difference is that a uni-lateral rupture will produce twice the shaking period as a bi-lateral rupture
Uni-lateral --- Rupture on the fault starts at one end of the rupture zone and propagates primarily in a single direction
Bi-lateral ----- Rupture on the fault starts roughly in the middle of the rupture zone and propagates roughly equally in both directions

Lets initially ignore the cluster of events up of the Cape Campbell area as they are associated with different fault(s). We will look at the main shock, SE of Hanmer Springs and the following aftershocks that trend to the NE through the Kaikoura region and then offshore. In the case of this event, neither the seismograms, nor the aftershock sequence suggest a multiple event. Rather they both suggest a single event and most likely a uni-lateral rupture.
It can be seen from the aftershock distribution that there are very few events to the SW of the main event. The vast majority of them are to the NE, up to and off the coast beyond Kaikoura.
The rupture has most likely to have occurred on the Hope Fault that I have high-lighted in yellow. Don't be too put off by the designated locations of the events relative to the fault, there is going to be a reasonable error in their location and also, since they were a little deeper (~ 25 - 35km), some of them ( including the main event) could well have been down dip on the fault plane to the south east.

At this time, I am pretty confident that the Hope Fault will be the nominated source of the event. It's the only obvious major fault in the area. I would suggest that, tho it is possible that the event occurred on some hidden fault line, it would be highly unlikely.
Considering the size of the event, it is...
1) likely that wouldn't have been the first event throughout history
2) would require the presence of a major fault that is unlikely to have remained hidden for millions of years.more to come ...

 

[CapnGranite]

This article seems to put the seismic activity into some perspective:
http://thespinoff.co.nz/science/16-...-at-least-six-ruptured-in-the-kaikoura-quake/

 

[davenn]

This article seems to put the seismic activity into some perspective:
http://thespinoff.co.nz/science/16-...-at-least-six-ruptured-in-the-kaikoura-quake/

There are problems with some of that

specially the fact that none of those smaller faults could produce a M7.8 event ... that requires a larger fault like the Hope Fault

I am pleased that they confirmed my uni-lateral rupture mode

I have no issue with the multiple minor faults activating and even rupture hopping between several more significant faults.
That isn't unheard of, a classic example is the Southern California, M 7.3, Landers quake of 1992 ...
This event was a uni-lateral rupture that jumped across several faults as it propagated to the NW.

here's another article on the NZ event

http://blogs.agu.org/tremblingearth...w-zealand-earthquake-part-1-seismology-night/

 

[StevieTNZ]

This is really really shocking http://www.stuff.co.nz/national/nz-...ngs-cordoned-off-over-earthquake-safety-fears

The amount of buildings off limits is going to bring the city to a stand-still.

 

[Astronuc]

From a related article - The Kaikoura earthquake lifted long strips of coast out of the sea on Monday morning, in parts as high as two metres.
http://thespinoff.co.nz/featured/17...es-out-of-the-ocean-coastal-uplift-explained/

Much of the northeastern coast of the South Island was uplifted during the 14 November earthquake. We know this from photos of rock platforms covered in seaweed and marine animals such as crayfish and paua stranded above tide levels. Our records measured the tide gauge at Kaikoura was lifted up by one metre, and continuous GPS monitoring sites at Kaikoura and Cape Campbell were also raised by 0.7-0.9 m. At this stage we can estimate that the coast was raised between 0.5 m and 2 m from about 20 km south of Kaikoura all the way north to Cape Campbell.

That's impressive!

Of course, it's better than the opposite.Possibility of another large earthquake in future - but where?

Geonet has released newly calculated aftershock probabilities that put the chance of one or more M6-6.9 quake in the next day at 37%.
http://thespinoff.co.nz/society/15-...t-probabilities-of-major-eqnz-in-coming-days/

A few of NZ's larger earthquakes involve jumping from rupture on one plane to another in a complex sequence. It was first seen with the Darfield September 2010 quake where multiple segments ruptured together as a single earthquake. It appears to have been the case in the Kaikoura earthquake.

Some probabilities of future quakes are given.

 

[cosmik debris]

This is really really shocking http://www.stuff.co.nz/national/nz-...ngs-cordoned-off-over-earthquake-safety-fears

The amount of buildings off limits is going to bring the city to a stand-still.

Yes, and it isn't as though nobody knew this. I mean if Christchurch wasn't a big enough hint. An earthquake closer to Wellington than this will not only destroy the infrastructure but will kill a lot of people. Wellington will be totally isolated, there aren't many roads in or out, the airport will definitely be out of action and probably the port as well. All that realized land is a real hazard too.

 

[StevieTNZ]

https://www.tvnz.co.nz/one-news/new-zealand/strong-magnitude-5-quake-strikes-kaikoura-region

A strong magnitude five earthquake struck the Kaikoura district shortly before 8pm tonight (yesterday evening).

I was walking along the beach front at that time and didn't feel anything. Luckily it seems not much, if any, damage was done by it.

I've yet to go into Wellington and see first hand what the state of the city is like. I know that the ports have been quite damaged compared to damage done by the Seddon earthquakes back in 2013.

 

[Astronuc]

As if Christchurch has had enough http://www.stuff.co.nz/national/86758316/christchurch-shaken-by-severe-earthquake

GeoNet has it at 5.69 Mag - http://www.geonet.org.nz/quakes/region/newzealand/2016p881669

Universal Time November 22 2016, 5:13:34
NZ Daylight Time Tue, Nov 22 2016, 6:13:34 pm
Depth 7 km
Magnitude 5.7
Location 15 km south-east of Culverden
Latitude, Longitude -42.88, 172.99

Canterbury Quake Live describes it as: 7 km north-north-east of Scargill, Canterbury, New Zealand; The distance from central Christchurch is 78.24km.
http://www.canterburyquakelive.co.nz/Browse/?reference=quake.2016p882664

5.7 quake closes Inland Road to Kaikoura for assessment
http://www.stuff.co.nz/national/nz-...closes-Inland-Road-to-Kaikoura-for-assessment

There's already a lot of damage to repair.

 

[StevieTNZ]

The low level of aftershocks following the 7.8 magnitude Kaikoura earthquake is "unusual" according to GNS Science.

https://nz.news.yahoo.com/top-stories/a/33288786/kaikoura-aftershocks-unusual-gns-science/