EQNZ Strikes Again

Yeap, it happened again:

A deep fault system in North Canterbury region has left rip just after midnight NZ time, resulting in minutes of strong, rolling, shaking felt through much of NZ at magnitude 7.5, and 16km deep. This then triggered multiple severe aftershocks in the Kaikoura Fault Zone, ranging from 5.0 to upper 6’s, along with smaller quakes across either side of the Cook Strait.

Damage reports thus indicate some building damage, no loss of life reported as of yet, but multiple reports of roading damage have come in and State Highway 1 is likely blocked in multiple places by landslips, cracks and rockfall. Hamner is presently cutoff, as are other inland towns/settlements. A minor tsunami warning has been issued, but waves appear to not be enough to top high tide levels. Evac warnings are however in place for areas immediate

As for what it felt like in Christchurch - I thought, at first, the Alpine Fault had finally let rip, since the shaking lasted for upwards of 4 minutes and was strong enough to make me lurch side to side. Checked geonet to see it was to the north of me.

And of course, it’s still bloody shaking while I’m writing this: http://www.geonet.org.nz/quakes/felt

Here’s hoping it doesn’t put stress on the big surface faults in that area though, as The Hope Fault is big enough to cause some serious damage.

When I first read this, I thought you mean some company messed up and did something that caused earthquakes. Reading the links, seems like it is just a series of natural quakes causing havoc over there?

Good luck and stay safe, really bizarre.

Heh, well I did write this while extremely tired so didn’t realise that not everyone would get the EQNZ bit, which is off the twitter #EQNZ/#eqnz that started up after the prior quakes that struck Christchurch.

And thanks - so far it looks like only 2 people have died, though thousands are stranded by slips and fault movements (there’s been some epic geology porn) that have destroyed state highway 1 in multiple places. Relatively few buildings collapsed too, mainly due to the peak ground acceleration only being 1.2G. With one house thrown 6m off it’s foundations as it was built on a fault line that ruptured in the aftershocks, though it was built before the fault was discovered.

As for aftershocks - the whole fluffing Marlborough Fault System and offshore faults that comprise the complex boundary interactions of the Pacific and Indo-Australian plates is popping off smaller quakes. Which has resulted in some major vertical and lateral movements. Case in point, parts of the Kaikoura coast seem to have been up lifted by ~4m, while GPS measurements picked up 2m lateral northwards movement at Cape Campbell (east of Lake Grasmere). With numerous other faults contributing in the area to land deformation.

And it’s still rolling as I write this, with aftershocks hitting every 1-2 minutes or less: http://www.geonet.org.nz/quakes/felt


Some more info:

  • scroll down for a video that shows all the after shocks, beware the auto-playing video’s Stuff stupidly has in place though, as long as you don’t get your mouse pointer on them they wont auto-play.
  • bits and pieces, but the most important bit is the video further down that shows the extent of lateral movement on the Kekerengu Fault. Hasn’t been measured yet, but the estimate is 10m of lateral movement.

From: https://www.reddit.com/r/newzealand/comments/5cy025/deformation_produced_by_the_m78_new_zealand/
As you can see, the whole NE of the South Island of NZ has moved considerably.

And here’s some of that uplift: http://imgur.com/a/xx6JV
These rocks are now 2m above the low tide line, possibly more in other areas due to local faults causing more uplift, like at the southern edge of the flats of Kaikoura. Basically any purple you see in pics of slips on the Kaikoura coast is from uplifted rocks. Heck, SH1 was basically built in many places on that coast on land created by similar uplift. While much of the downtown of our capital Wellington is built on similarly uplifted land.