Sink holes, cracks, lateral spread, elevation changes and liquefaction

Posted in Personal Finance July 23, 2012 - 09:35am, Janine Starks
By Janine Starks*

When it comes to land claims one large group of homeowners have the most unanswered questions and the most uncertainty; those sitting on liquefied land.

Not enough time has been spent asking EQC and insurers detailed questions about liquefaction. So a few weeks back, I dived into the mucky stuff and tried to clarify a host of questions readers have posed.

As is often the case, the deeper you dig, the more you realise you’ve disappeared down a hole. So with sink holes, cracks, lateral spread, elevation changes and liquefaction in mind, here are the issues we discussed:

What is land damage? Gosh that sounds like an odd question. Don’t most of us think that liquefaction has altered the pre-quake condition of land, therefore it’s damaged?

But we need to take a step back. Our definition of damage might not be the same as EQCs.

Their view is that land damage “means a not inconsequential change in the land, caused by natural disaster, which affects its utility”.

The important word here is “utility”.

Can you still use it? In short, if you can still use it (i.e. there is foundation solution which supports a rebuild), then it’s not damaged.

Surely if you have 10 or 20 metres of liquefied soil beneath your lawn and house, before a solid layer is reached, you have damaged land? No, apparently not.

Concentrate hard on this next sentence. “Liquefaction is a process not an outcome”. As EQC explain “Land will only liquefy and eject sand and silt above the surface, during an earthquake. Once the earthquake has finished, the land resolidifies”. While EQC won’t go so far as claiming that your land is back in its exact pre-quake condition, the fact that the silt goes solid means it is now viewed as useable and undamaged.

EQC see no need to remediate the soils below ground level.

They tell me the vast majority of people will only get the surface damage fixed - that is, sink holes and cracks filled in, silt removed and ponding fixed. This has been well covered in the media as the ‘rake and roll’ technique.

There will be very few people whose land is uneconomic to repair and who will receive the maximum payout under the law (that is, generally a cash payment to the value of the smallest allowable section size in the local area – of which there are 19 different sizes in various areas).

Will EQC fix liquefied land to make it less susceptible to new doses of liquefaction? In short, no.

The solution is restricted to ‘rake and roll’. If land is no more susceptible to liquefaction than it was prior to the earthquakes, they will not ‘better’ it by building it up or strengthening it. Even land that has had repeated doses of mud and silt will not be strengthened.

It seems if your land is ‘more susceptible’ to liquefaction you may have a case for strengthening. This one ties EQC up in knots. How do you prove pre versus post quake susceptibility? Being a fan of simple answers, I quote the obvious example of streets where heavy trucks now cause liquefaction to rise forth.

Pre-quake, a truck could drive on these streets with no side effects. It seems clear that plenty of people could prove they are now more susceptible. EQC explained that a geotechnical engineer will decide on this and their work is being reviewed by experts at Universities such as Canterbury and Berkeley in the US. While that’s admirable, I hope the professors take the ‘truck-test’ into account. Unless ‘susceptibility’ is tested legally, EQC probably don’t have much to worry about. Cantabrians are proving to be rather limp-wristed in their willingness to litigate or form action groups, so I doubt this one will get tested.
Will EQC fix a change in elevation if land has sunk? Again no.

If the ability of the landowner to use the land has not changed, the solution will be restricted to fixing any observable surface damage.

If an elevation change has occurred in the Flood Management Areas (FMA) like Redcliffs, Southshore, Sumner and river suburbs, EQC have obligations. Check on the councils website to see if you are in the FMA as rebuilds are likely to prove a challenge. Rumour has it the council will widen the net and capture more homes in the FMA due to land sinking in the quakes.

Homeowners have ‘existing rights’ for earthquake rebuilds and can skirt around the need for resource consent.

But building consents may catch you, as the floor level must counter a 1 in 50 year flood (your old house may be beneath this).

The new rules mean you have to counter a larger 1 in 200 year flood. Land that has sunk in the earthquakes will need to be raised by EQC or an alternative solution negotiated between EQC and insurers. Sounds messy doesn’t it. Even messier when you consider the volume of homes in these areas.

Will land damage be categorised using a new scale? EQC were unable to offer any comment on this. Reliable sources tell me it will be.

The new categories are likely to be labeled Category 1 through to 9 with 1 being the least damage and 9 requiring more difficult solutions. You can find early evidence of this in the original Tonkin & Taylor reports but the categories were in reverse. The rumor mill says insurers are very wary of carrying out rebuilds in the 8 and 9 categories and these may in some way be linked to the Flood Management Areas around the rivers and coast where land has sunk. Insurers and EQC will need to negotiate higher floor levels versus the practicality of building land back up.

Are insurers beginning rebuilds on liquefied land?

Some insurers have started planning rebuilds in Green-blue areas (TC3) on the basis they have been in the 1-7 categories, with no elevation change and are not in the Flood Management Areas. We can only guess that these categories will become more evident as land assessments are revealed to homeowners by EQC. For now they are silent on the matter. The new categories can’t come soon enough. There has been too much confusion over TC2 and TC3 land. These labels only reflect how susceptible land is and what foundation solution is required. They don’t tell us the real level of physical damage.

When will land assessments be completed for those who have suffered liquefaction? They are complete. All the work is done and has been for some time.

EQC have completed over 56,000 land inspections in the hardest hit flat-land areas. Inspectors have gone door to door – if you didn’t see one, you will have been at work (or you owned a big dog that scared them off). While there are engineers currently carrying out drilling all over the Eastern suburbs, this data is not required for land assessments – it’s solely to determine foundation solutions.

EQC are sitting on all the data they need. They’ve done aerial flyovers and have previously completed 2000 drillings to give the elevation changes. Combine that with the visual house-to-house visits and it’s all done. The missing link is they haven’t yet designed a model that determines how remediation and compensation will work. This will be available at roughly the same time as the completion of the drilling for foundation solutions, so the two elements will roughly run in tandem.

What are insurers doing regarding carrying out their own GeoTech reports?

Insurers have been very slow to move in TC3 areas. On one hand it’s because of the continued seismic activity making the risks too high. On the other hand they could get off their chuffs, send in their own GeoTechs and start the planning phase. I’ve asked insurers what is causing the stalling and they tell me it has nothing to do with a lack of resources. At the drop of a hat they can get as many GeoTech rigs and people as they need. Instead, they prefer to wait for EQC to release their area wide land assessments in the hardest hit suburbs.

On digging a little deeper there seem to be a couple of reasons. First, on some sites where shallow foundations and light-weight cladding can be used, they believe there will be no requirement to individually drill those sections. On other sites where heavy brick veneer is being rebuilt, or deep pile foundations are needed, they will need individual GeoTech reports.

If insurers wait for EQC to release their results, they can concentrate on drilling only those sections that require it. Second, they are very concerned about category 8 and 9 land damage and want to work closely with EQC on this. Just to be clear, this is the insurers point of view – whether it’s contractually acceptable to delay is another matter.



Let the CCC know if your house is demolished for rates reduction

Make sure your rates bill is up to date by letting the Christchurch City Council know if your house has been demolished.

The Council will have your property revalued if a house is demolished, and adjust next year's rates bill accordingly - this can mean a significant reduction in rates. Current legislation and Council policy do not allow the Council to adjust rates within the financial year.

Council's General Manager Corporate Services Paul Anderson says that many demolitions occurred without consent immediately following the earthquakes and the Council may not be aware if a house has been knocked-down or removed from a property.

"If we don't know about it, we can't update your rates account," Mr Anderson says. "By calling the Council and letting us know about residential demolitions, we can ensure you are paying the correct amount of rates.

"We are doing a lot already to keep ourselves as up-to-date as possible on demolitions, such as collecting demolition information from CERA and through the Council's call centre. However, there may be a large number we still don't know about.

"While the Council can adjust rates retrospectively, it is easier for residents and for our staff if we get it right the first time," Mr Anderson says.

Residents can call the Council Call Centre on 941 8999 or 0800 800 169, and ask for the rates team, to let the Council know if a house has been demolished.

In addition to adjusting the capital value of properties where a building has been demolished, the Council is also seeking permission from Central Government through an Order in Council to further change the way rates are levied throughout the year. The aim is to allow the Council to adjust rates throughout the year to reflect when a new house is completed, as well as reducing rates levied to land value only once a building has been demolished. Rates are calculated on the combined value of the land and any structures on that land (the capital value). At the moment, the rates can not change throughout the year even if structures are built that would increase the capital value.

While the Council is waiting for the Government's approval for this Order in Council, which would allow us to change rates throughout the year, the Council is using the Rates Remissions Policy it put in place to provide rates relief to the most affected ratepayers. This policy provides for:
  • 40 per cent rates remission for residential properties that are unable to be occupied.
  • 30 per cent rates remission for businesses located within the cordoned Red Zone.
  • 30 per cent rates remission for businesses outside the Red Zone that can not be occupied because they are adjacent to dangerous buildings.
  • 100 per cent rates remission to owners of Port Hills properties at risk of rockfall, cliff collapse, unsafe access and who have been instructed by the Council to leave their properties under section 124 (1) (b) of the Building Act Source


If I have to demolish a property, is there anything I need to do regarding my wheelie bins?

The kerbside collection wheelie bins belong to the property they were allocated to. Each bin has an address label on the side with the property's address and a serial number linking the bin to the property.

Contact the Council's Call Centre (03) 941 8999 or 0800 800 169 and advise when the dwelling on the property will be demolished and when the wheelie bins need to be removed.

The bins will be removed by the Council's kerbside collection contractor and returned once the property has been rebuilt. There is no cost for this service.

Green Recycle Bin
We have large green bin - cost $174 per year this is up for renewal in March 2012. We have just signed papers for Demolition and rebuild of our property in TC3 Blue. 

Q.    Can we suspend our contract for 6 mouths during demolition and rebuild?

A.    No.    You can take bin with you or give it to someone else.

Q.    These are different times, this is extremely inflexible, we will not be the only people in this position.

A.     Pay in full or return the bin.


Foundation checks in blue-green zone

Technical assessments on foundation damage will begin for the more than 8000 homes in Christchurch's residential blue-green zone in the next six to eight weeks, the Earthquake Commission [EQC] says.

EQC customer services general manager Bruce Emson said yesterday all TC3-category properties with confirmed foundation damage would be assessed, which could result in customised foundation solutions being required.

The technical assessments were part of the commission's joint efforts with private insurers to advance settlement of claims.

They would help the commission and private insurers determine the cost of foundation repair or replacement as part of customers' building claims for quake damage, Emson said.

The assessment will include on-site drilling and an off-site geotechnical analysis.

"The drill results will require analysis by a geotechnical engineer in order to establish the best foundation solution for the property. Once analysis is completed, a structural engineer may be required to design the foundation solution on a case-by-case basis."

The process would take time, but the aim was to provide some certainty for TC3 landowners.

"EQC, private insurers and the Department of Building and Housing are all moving . . . quickly . . . to work out the best repair or rebuilding solution for customers in the blue-green zone," Emson said. Source


Brookhaven residents meeting - 31 January 2012

Over 500 people came again. Most I spoke to thought it was very good.

After intros Ivan Lafeta from Cera opened talking about TC3 and doing a recap on how the land zoning was worked out using Lidar. We then had Jan Kupec Cera's land guru who was incredible. Best I have ever seen on explaining the differences between our land and that which was redzoned and why. He was a highlight of the meeting for me.

Reid Stiven from EQC then talked on the Cash Settlement process should you be unable to rebuild on your land (this is different from the Red Zone one). We were also given an update on how the geotech is expected to work.

John McSweeney (AMI) and Dean MacGregor (IAG) then tag teamed to cover the submitted questions for insurers. To close we had Patrick Schofield from CCC give a very detailed rundown on Variation 48.

The above was an hour and a half so really covered alot. There was then half an hour of question time and the meeting closed at 8.05pm when people were able to talk to the speakers (and the huge number of welfare support staff Cera had made available at the rear of the room).  Source


Canterbury's Seismic Activity - What You Need To Know
Watch this YouTube video with Bob Parker Mayor of Christchurch interviewing
GNS scientist Kelvin Berryman and Professor Jarg Pettinga, from Canterbury University's geological sciences department after the earthquakes on 23 December 2011. Click Here


Earthquake Recovery and Rebuild Update
Nicky Wagner, National MP for Christchurch Central - 9 January 2012

Hi Everyone,

Happy New Year….although we have been rocking and rolling ever since before Christmas I do believe that 2012 is going to be a much better year for all of us in Canterbury!

I have had a ‘on again’ and ‘off again’ break and was back in Christchurch to get the latest update from the Geo-Tech scientists. Here are the details for your to mull over.

Christchurch is likely to experience more magnitude five or six earthquakes during the coming months but larger earthquakes are likely to be further away from the city causing less damage, experts say.

The latest earthquakes which have been occurring off the coast in Pegasus Bay are also unlikely to produce a large earthquake of magnitude seven, resulting in a life threatening tsunami.

GNS Science and Tonkin and Taylor experts today briefed the city’s elected members, local Members of Parliament and media about the latest seismic information at a meeting in the Christchurch Events Village in North Hagley Park. Mayor Bob Parker called the meeting following the latest aftershocks which began on 23 December 2011.

GNS Science Earthquake Scientist Kelvin Berryman said, “Our expectation is that the current sequence of earthquakes will start to decrease over the coming months and certainly we believe that a lot of the stress has already been released on the fault lines closer to the city. We believe we are progressing into a period similar to after the February and June 2011 earthquakes. They will go on for some time but they will become undetectable over time.”

He also said that the risk of tsunami had not changed as a result of the recent earthquakes. “From the information we have, a local source tsunami from an earthquake fault in Pegasus Bay is thought to be unlikely.”

Other key points made at today’s briefing include:

  • The magnitude six earthquake that occurred on 23 December was only slightly above what scientists had predicted. Scientists have previously said that there was a 50% chance of a magnitude 5-5.9 earthquake occurring in the coming year.

  • The probability of a magnitude seven earthquake is low.

  • The peak ground acceleration (a measurement of how hard the ground shakes) is decreasing. The peak ground acceleration during the 23 December aftershocks was less than the 13 June aftershocks and significantly lower than that experienced during the 22 February earthquake, which caused significant building and ground damage.

  • It is difficult to predict how long the region will continue to experience earthquakes but it could last for up to several decades. However, they will become undetectable except on sensitive instruments over time.

Earthquake activity since September 2010

The seismic activity has occurred across the Canterbury region and is not isolated to Christchurch city.

Refer to the ‘most recent aftershock map’ at  which shows the distribution of earthquakes since 4 September 2010. See map below:

It is important to consider seismicity across the whole Canterbury region. As can be seen in the map above, the earthquakes have migrated since September 2010across the region, generally from west to east (refer to map key for time sequence).

The initial earthquakes were located along the Greendale Fault and within Christchurch city, but since February 2011 the location of the earthquakes has moved southward (June events) and east December and January events. GNS Science advise that this migration pattern is expected and they predict that the location of the earthquakes may continue to move further east and out to sea.

The probability of a magnitude 5.0 – 5.9 earthquake is likely to have increased slightly after the earthquakes of December 2011 and January 2012. GNS Science will provide details of the updated modelling by the end of January and will release this information to the public. GNS Science predict that the probability of a magnitude 7.0 earthquake or above is low.

GNS Science predict that the likelihood of a tsunami as a result of an earthquake in the Canterbury region has not changed since modelling was completed in April 2011. A tsunami is unlikely unless an earthquake is located offshore, close to Canterbury and measures 7.0 magnitude or above. Any tsunami would result in the maximum of a one to two metre high wave, except in bays on Banks Peninsula where some increase can be expected, and where residents have been individually advised.


Why are the earthquakes located in different places in Canterbury?
Seismic activity has occurred across the Canterbury region and is not isolated to Christchurch city.

Refer to the ‘most recent aftershock map’ at  which shows the distribution of earthquakes since 4 September 2010. It is important to consider seismicity across the whole Canterbury region.

The initial earthquakes were located along the Greendale Fault and within Christchurch city, but since February 2011 the location of the earthquakes has moved east. GNS Science advise that this migration pattern is expected and that the location of the earthquakes may move further east and will be located out to sea.

Most of the recent earthquakes seem to be located at a depth of eight to 10 km. What does that mean?

In the Canterbury region, Greywacke rock is located at a depth of eight to 10 km and is over 100 million years old. This rock is very old and fractured and this is where most of the earthquakes are located.

The earthquake on 23 December felt different to the earthquakes in February and June 2011. Why is this?
There are a number of factors which affect how an earthquake feels, but one key change was the decrease in ground shaking levels. This decrease is expected because they were deeper than earlier events, were smaller in magnitude than February in particular, and were at greater distance from populated places. There are also some preliminary indications that the recent earthquakes have contained less energy at their source. GNS Science expect that the levels of ground shaking will continue to decrease, especially if the earthquakes are more distant and have similar 8-12 km depth..

Are we likely to have another ‘big one’ – an earthquake over 6.0 magnitude?
GNS Science predict that we are most likely to experience further earthquakes of 5.0 to 5.9 magnitude, but there is a low probability that we will experience further earthquakes of magnitude 6.0 and above.

GNS Science advise that the energy which has been released to date is now in line with what would be expected at this time so that ‘we have caught up’ on the level of energy which was expected to be released following the Darfield earthquake of September 2010.

However GNS Science predicts that we will have an ongoing but slowly decreasing level of seismicity for several decades. While the earthquakes will not suddenly stop, the events felt by residents will reduce in frequency progressively from the levels experienced over the last 12 months. They will become undetectable over time.

GNS Science predict that events will continue for some years and if there is a magnitude 6.0 earthquake, then it is unlikely to be located within Christchurch city due to the trends to date.

For further information regarding seismicity in the Canterbury region since September 2010 visit 


What is the local tsunami risk in Christchurch and Pegasus Bay?
The risk is low in Christchurch and Pegasus Bay and has not changed as a result of the recent earthquakes.

From the information that GNS Science has, a hazardous local source tsunami from an earthquake fault in Pegasus Bay is thought to be unlikely.

However it cannot ruled it out completely. If you are near the coast and feel strong ground shaking that lasts for a minute or more and it is hard to stand up, then an excellent precaution is to move inland or to higher ground as quickly as you can, using the safest route that you can.

So, that is the latest. Probably nothing too new but it was good to get an update and I felt reassured that we are through the worst of this seismic episode. It’s amazing how much information we have all absorbed about earthquakes over the last year or so.

I know that there are people who are in still in limbo and are very stressed because they can’t make decisions about their homes, or their futures. But we are slowly making progress, and I promise we are doing everything we can to get certainty for everyone as fast as humanly possible.

All the best

National MP for Christchurch Central, 222 Bealey Ave, CHRISTCHURCH