Monday, 15 August 2011

13th June 2011 ~ Christchurch's third major earthquake event

I've put off writing about this third major event for some time - it's all been too much.  I'm doing so now to record what happened, as already many of our memories are becoming vague as to details and about what happened in which earthquake. 

Although I moved from Christchurch some years ago it is where I grew up and I am close to people who still live there.  So much of the loss is personal and with each new big shake fresh damage occurs and the nerves of residents are tested yet again. 

The quake event of the 13th June consisted of two big shakes: the first at 1 pm, was Richter magnitude 5.6  (Moment magnitude 5.3), followed by a much more severe one at 2.20pm, which was Richter magnitude 6.3  (moment magnitude  6.0).  Note that the degree of magnitude has been revised a number of times; this set is the final one.
     The use of the two different magnitude scales is confusing.  While there is an intentional degree of similarity between them they do measure different things.  Essentially, the Richter scale measures ground motion whereas the moment magnitude scale measures the amount of energy released.  Here is what the Wikipedia article has to say about them.  Scroll down the article to read comparison of the two.

The eastern suburbs were worst affected, among them Bexley, Bromley, New Brighton and Parklands, where liquefaction sent fresh fountains of water and silt gushing out of the ground.  Further to the east and across the estuary the cliffs of Redcliffs, Clifton and Scarborough suffered major fresh collapses, sending up clouds of dust as they crashed down.  Electricity was lost to large parts of the city and newly laid sewers broke once more.  Many who were standing at the time were knocked off their feet, and those who were sitting were thrown from their chairs.

In Bromley, this footage from a shop's closed circuit television shows the earthquake as it occurred at the Dyers Pass ITM Building Centre.  You might like to mute the sound for this one as it's an odd and distracting choice.  Here we see ordinary people attempting to live life as normal when...

Getting out of shaking buildings wasn't the only concern.  Getting home was another and completely different challenge.  In the clip below we see footage of liquefaction in the eastern suburbs as it happened - I used to live in this area!  You can see how rapidly the water level rises, and holes open up in the ground.  On flooded roads one has no clue as to where these holes may be: 

In the next clip a Tonkin and Taylor spokesman describes the damage to this land. This clip is from the Canterbury Earthquake Recovery Authority site.

The Campbell Live news show which screens at 7pm on weekdays has provided much excellent coverage of earthquake events and difficulties from many angles.  In the following item John Campbell takes us on a visit through earthquake-battered Bexley.  We see exactly what it's been like to live with liquefaction and how the interiors of many houses have been affected, with liquefaction occurring inside as well as outside.
Across the Estuary in the Sumner area we see damage of a different kind - collapsing cliffs: 
This is what the cliffs along Wakefield Avenue looked like just after they had collapsed. The man who filmed them apologizes on YouTube for language used at the time.  I think this can be overlooked under the circumstances!  My sister was standing just metres away and the quake knocked her off her feet.  She said she had no time to grab anything to hold onto, that the ground "just leapt up and hit me".  She said that the cliffs both hissed and roared as the rock faces fragmented, and that thick dust covered everything, making people choke.  

Given the amount of debris that must have been flung long distances, it's not surprising that the authorities had a double height avenue of shipping containers placed along the inside of Wakefield Avenue: 

A selection of photographs taken when I was in Christchurch in late July show more images of this area as well as the central city and will be published in a companion article.
In the clip below we see the state of the collapsed cliff face along Whitewash Head - from the top! I sincerely hope that the person who filmed this never does anything like it again - it's exceedingly dangerous terrain! 

Further round Clifton suffered severe cliff-face collapses as did Redcliffs.  One philosophical home owner whose property is near the edge of a precipice remarked that the Bible cautions us not to build our homes on sand, but on rock; he pointed out that the quakes have proved both to be unsafe!

Central Christchurch, already badly damaged, with much of it still cordoned off, deteriorated further.  This is what remains of the Stone Chamber of the Canterbury Provincial Council Buildings, a highly regarded heritage site:

Christchurch residents are becoming less sentimental.  A handful of heritage buildings will be salvaged or rebuilt, but most will not. 

Aftermath - TV3 footage from around the city:
Note: the cliffs shown are Clifton, at the main cliff top opposite the ocean, and sadly below, on Peacock's Gallop.

The following news stories give an overview of the quake:

    Earthquake aftershock frequency and scientific explanations:
    At the time of writing, Christchurch has experienced 29 earthquakes of Magnitude 5 and above, since 4th September 2010.  You can count them for yourself on the Geonet site which lists these as 'significant Canterbury earthquakes'.  In total there have been 8319 quakes recorded on the Christchurch Quake Map.  The degree and severity of the on-going quakes is most unusual.  Each time there is another major quake event the clock for the pattern of reducing aftershocks is re-set back at the beginning.  Everyone is wondering how much longer this is going to go on.  The answers are uncertain, but scientists give a measure of insight:
    Scientific discussion is always helpful, and the people of Christchurch are becoming experts in their own right.  The forum 'Ask a scientist' hosted by the Press is very helpful.  It's worth scrolling through the articles to look at the different questions put:

    Earthquake stress:
    The people of Christchurch are wearing thin with the stress of continuing earthquakes and the resulting loss of so much: their city centre, community shops and other facilities; significant areas of the city have not had sewer connections since September last year; and many residents have lost not only their homes but their livelihoods as well. 

    People react and cope in very different ways:
    It has been observed that the people of Christchurch have been drinking more in an effort to cope.  This group manages to keep it positive:
    • Christchurch neighbours in good spirits after quakes - the residents of Arnst Place in Dallington keep up their good cheer with get-togethers over a tot of rum - Campbell Live, screened on 22nd June 2011. All houses in their street have since been scheduled for demolition.
    Here is the remarkable story of Raewyn Iketau, who embraced the difficulties of living in abandoned central Christchurch - until after the 13th June:

    Time delays in repairing and rebuilding have been immensely frustrating for many residents.  Delays have occurred for many reasons.  Some of these are:
    • Nearly 600 buildings in the central business district have been approved for demolition with dumped material expected to be approximately two million tonnes.  A large portion of central Christchurch remains cordoned off until these are cleared and others are made safe.  
    • The sheer volume of waste needing to be removed from around the city is massive, and all this takes time.  The Christchurch City Council media release Recovery park to sort earthquake waste of 18th July gives these figures - Christchurch City Council media release of 18th July gives these figures for earthquake waste:
    Currently earthquake demolition waste received at Burwood Resource Recovery Park:
    • 200 – 300 trucks a day each carrying approximately 25 tonnes of waste.
    • This equates to 5000 – 7500 tonnes of construction and demolition waste being received each day.
    Estimated total demolition waste created by the 22 February earthquake:
    • Central Business District – two million tonnes.
    • Residential and suburban commercial zones – two million tonnes.
    • Repair of roads and water and sewer pipes – four million tonnes.
    • Sand and silt collected from streets and properties – 500,000 tonnes.
    • The owners of buildings scheduled for demolition may have protracted negotiations with insurers as well as EQC (The Earthquake Commission), and the buildings then take time to be cleared away.  It is expected that The Grand Chancellor Hotel may take up to a year to take down, floor by floor.  It is in the midst of a heavily built up city area so it can't just be pushed over.  Until this and other high rises are taken down the smaller businesses surrounded them are ham-strung. 
    • Insurance difficulties are emerging as the top stymie to the city's rebuild, with builders as well as home owners being unable to get further insurance:
    • Land that has suffered severe liquefaction or other severe damage has to be stabilized by a process termed 'remediation' before it will be suitable for building on once more.  This cannot be done while buildings remain on sites.  Remediation is expected to take years.  
    • Those whose homes are on or at the foot of the hills within rolling distance of unstable rocks must wait for these to be removed or secured, an enormous task which is likely to take a very long time.  As many as 150 homes which have suffered rock damage may have to be demolished.  
      • Big boulders hard to budge - this article from The Press describes the work being down in the Sumner hillside area, published on 30th June 2011.
      • Earthquake update for Port Hills reserves - Christchurch City Council posting of 5th August 2011. This article describes the process of dealing with loose rocks, and the scale of the task.
      • Rockfall threatens 150 homes - Article from The Press published on 11th August 2011
      • 250-tonne rock sent crashing - article from The Press published on 24th August 2011. This includes a video clip of a massive rock being dislodged by experts from the cliff-top behind Sumner's Marine Tavern.
    •  The sheer number of assessments being handled by the EQC is mind-boggling: 128,000 as at the 22nd July!
    • Legal issues are likely to be an additional source of complexity for many property owners.
    • With such a large proportion of buildings across the city needing attention this represents a massive amount of work for tradesmen who are already in high demand. Rebuilding will continue for years.

    Related news articles:

    The way we were: 
    Oh, for the good old days, and an orderly city where everything worked.  This delightful video is a unique contribution to Christchurch's pre-earthquake memorabilia, for which many thanks go to 'lukaskaupenjohan'

    The new draft plan for the city was announced on the 11th August:
    We all look forward to better times ahead.

    Living with uncertainty: 
    New Zealand is a land on the move.  Severe earthquakes in heavily populated areas are rare, but always a possibility.
    • Great Alpine Fault Earthquake - an article posted on the Otago Regional Council website gives a summary of a talk given by Tim Davies, Associate Professor from Canterbury University, 8 - 10 October 2007.
    • Ask an expert: Alpine fault fears - Forum for questions answered by scientists hosted by The Press - last updated 6th July 2011

    All my articles about the Christchurch earthquakes and aftermath can be found via the page linked to below, or at the upper right of this screen:


    Grace Dalley said...

    Regarding the magnitude, it's kind of complicated. GNS has been reporting Richter values (I can't imagine why!), which are 5.6 and 6.3. But the Moment Magnitude values for these 13 June quakes are 5.3 and 6.0, respectively. and

    Grace Dalley said...

    That TV3 item on quake rubble gives a figure different to that provided by the council in this press release:

    The relevant passage: "Estimated total demolition waste created by the 22 February earthquake:

    Central Business District – two million tonnes.
    Residential and suburban commercial zones – two million tonnes.
    Repair of roads and water and sewer pipes – four million tonnes.
    Sand and silt collected from streets and properties – 500,000 tonnes."

    Leigh said...

    Many thanks for clarifying these points, Grace - just the sort of info I've spent hours looking for! :-)

    Leigh said...

    Thanks once more to Grace Dalley for
    clarification of the above points. These have now been incorporated into the text of the article. :-)