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Earthquake — Parallax Forums

Earthquake

PublisonPublison Posts: 12,366
edited 2016-11-13 23:21 in General Discussion
As everybody has heard by now, the has been a significant earthquake in New Zealand.

I have been trying to email our friend, Hanno Sander, (creator of VeiwPort and 12 Blocks). My email to hannoware.com kicked back. Just tried onerobgot.org and it seemed to go throgh.

Hope everything is good down there. This is the third earthquake he has gone through.

Comments

  • User NameUser Name Posts: 1,451
    What about evanh? Have you heard from him?
  • PublisonPublison Posts: 12,366
    User Name wrote: »
    What about evanh? Have you heard from him?


    That's right. He is NZ.
  • ercoerco Posts: 20,256
    Wow, sorry to hear that. That is a ridiculous amount of activity. And I live in LA. Likewise, I hope Hanno & evanh and others are minimally affected.
  • evanhevanh Posts: 15,916
    Thanks for concern. I'm fine in Christchurch, we are maybe 100 km from the epicentre.

    I'm only just finding out myself how bad it really was. On the night, I turned on the radio to find out any details and one thing that was notable even then was that there was no one calling the station from the affected area. It feels more scary now in hindsight.

    7.5 is certainly getting up there! But it's also on one of the main fault lines so was always part of the predictions. I believe a mag 8+ along the alps is still due.
  • evanhevanh Posts: 15,916
    edited 2016-11-14 08:53
    Detail: There is a spread of aftershocks running up that fault line another 200 km or so, reaching up to the top right corner of the island. Some were big ones in their own right. Because of their location I think those did more damage to human dwellings that the initial quake.
  • PublisonPublison Posts: 12,366
    Got an email from Hanno. Good news is that they felt a gentle roll for about 2 minutes, but the tsunami sirens kept them up most of the night.

    No damage.
  • RS_JimRS_Jim Posts: 1,764
    Thanks Jim , hat is great news,
    Jm
  • ercoerco Posts: 20,256
    Incredible. Hope things calm down over there ASAP so help can get where it needs to go.
  • PublisonPublison Posts: 12,366
    Military is all out to rescue tourists who are stranded.

    http://sanfrancisco.cbslocal.com/2016/11/14/new-zealand-plans-rescue-of-tourists-stranded-by-earthquake/


  • geo_leemangeo_leeman Posts: 190
    edited 2016-11-17 13:04
    Interesting earthquake. The first part of my graduate work involved looking at electrical charge separation on faults during slip and if it could possibly explain anything about the phenomena of "earthquake lights" that have been observed during several major subduction zone earthquakes. The whole idea was thought of as a bit crazy until photos were taken by a scientist in the 60's during an earthquake sequence in Japan. This even had several recordings of them as well. Fascinating stuff. For the record we could create pretty large potentials from our lab earthquakes, but the conduction and coupling mechanism never got worked out and I moved on to work on the pure frictional dynamics of such systems.
  • Tracy AllenTracy Allen Posts: 6,664
    I spoke with a kiwi friend in Wellington, and he said he felt it more there than his sister did in Christchurch, despite the epicenter being closer to Christchurch. My wife and I passed through Kaikoura earlier this year. That is where the earthquake caused landslides from the coastal cliffs both north and south of town and cut it off so they had to do evacuations by helicopter and by sea. It's a pennisula famous for whale watching and rich marine life.
    Kaikoura.png
    1409 x 520 - 1M
  • evanhevanh Posts: 15,916
    Christchurch isn't feeling any aftershocks beyond day one. There must be a decent cushion between us and the main fault line.

    There is some head scratching going on over the amount of high-rise damage in Wellington given there wasn't a single aftershock in the area. And it was meant to be NZ's most quake resistant City.
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2016-11-18 02:22
    "There is some head scratching going on over the amount of high-rise damage in Wellington given there wasn't a single aftershock in the area" .... Hmmm ...

    ... an interesting side note, we have a fair amount of Earthquakes here in Oklahoma on a daily basis. A few things I have noticed that seem to be uncommon with a typical California earthquake is that you can sometime hear the earthquake before the ground shakes ... this sort of defies what I thought to be true in that the sound came after the ground moved... <-- Anyway it is what it is. Another observation which might apply to the high-rise is that many Earthquakes go undetected unless you are on the second floor or more of a house or building. I believe this might be caused when most of the ground motion is along the Z-axis and not so much along the X and Y axis. Just a theory. Fracking related quakes may cause more Z-motion in our particular case.
  • evanhevanh Posts: 15,916
    edited 2016-11-18 03:49
    Beau Schwabe wrote: »
    ... this sort of defies what I thought to be true in that the sound came after the ground moved...

    It's called the 'P' wave. The closer the epicentre the more you'll hear and feel the P wave. And the sharper the overall shake will be. It gives the first fright and often separates those that run from those that hide.

    Another observation which might apply to the high-rise is that many Earthquakes go undetected unless you are on the second floor or more of a house or building.

    That's also proximity based. The further away the epicentre the more it's just a rolling sensation. The edgy violence is totally lost. This recent 7.8 quake was quite the ride in Chch, in that it felt just like an ocean liner on a gentle long wave rolling sensation. It grew and I could feel the acceleration then deceleration in each direction. The ground under Chch must have been moving quite a number of metres back and forth. That's why I decided to check the radio.
  • TorTor Posts: 2,010
    Beau Schwabe wrote: »
    Another observation which might apply to the high-rise is that many Earthquakes go undetected unless you are on the second floor or more of a house or building
    That's exactly what I observe from my site in Japan. That area hasn't had a big one for ages, but we often feel earthquakes from farther away, but I've only ever noticed them when on the upper floor. And I remember the big one in Italy in 1997, I was on the sixth floor up from the ground floor in a big, square office building in Rome. The essentially cube-shaped bulding swayed like a pendulum up there. Quite a sensation.

  • Tracy AllenTracy Allen Posts: 6,664
    edited 2016-11-18 20:01
    Pendulum indeed. The shock and the wave excite natural resonance modes in structures. Like driving a tuned circuit or a compound pendulum. Our house is basically a box but has a smaller addition tacked on at the back. During the 1989 Loma Prieta quake the plaster cracked in the wall and ceiling next to the line where the addition attaches to the house, also at the opposite end of the house, at the antipode. I believe the addition has a different resonant frequency from the rest of the house, so it had its own response to excitation from the ground. The worst damage from Loma Prieta came in the San Francisco Marina district, which is basically a bowl full of jelly setting against bedrock, years and years of mud landfill. It is like a resonant amplifier of ground motion.

    Here is the video of three cows caught on a small steep mesa from the landslide near Kaikoura NZ.



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