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Saturday, 30 March 2013

Maps of lateral spreading and other earthquake effects in Avonside

Courtesy of a blog reader I have discovered a Tonkin & Taylor report on lateral spread in the Avonside Area. The full title is Appendix M: Avonside study area – lateral spreading. The EQC website is currently closed however you can download it from here.

On the same website, but this page here, is more geotechnical information arising from the Liquefaction Vulnerability Study (mentioned on the blog earlier in the month here). There is a huge range of stuff however, as Avonside is the only suburb for which there are detailed maps, possibly nothing informative for those in other Red Zoned areas.

The report is a collection of maps that show measured changes in height, and ground surface observations of liquefaction, ground cracking and lateral spread throughout Avonside. The time period of the maps is from September 2010 through to at least the June earthquakes in some cases, and December 2011 in others. The report itself is undated.

For those who have some doubts about what happened this is a good set of maps to check what you observed against what was recorded by Tonkin & Taylor. If you are stuck for a place to start try Map 6. This map shows the amount of land movement over the period. The longer the arrow the more movement there was (there is a scale for the arrows at the bottom of the map). If my eye-balling is correct then the land under Cowlishaw Street moved about half a metre and the land under Bracken Street moved well over a metre. Land under Dallington by the Gayhurst Bridge moved close to two metres.


Thursday, 28 March 2013

Chief Executive of the Insurance Council on various things

On Tuesday Tim Grafton, chief executive of the Insurance Council of New Zealand (ICNZ), gave an address to the Canterbury Branch of The New Zealand Insurance Law Association.

His address is available on the ICNZ website here, and is an interesting insight into how insurers see the world. As is his role, he puts the obligations, role and responsibilities of insurers in a positive light. Very positive indeed.

Towards the end a significant amount of time is given to what seems like special pleading on the issue of government’s Consumer Law Reform Bill, with a view to having the unfair contracts provisions removed. These provisions apparently represent a threat to the way insurers prefer to do business and there is no evidence of a need for legislation dealing with unfair insurance contracts.

For more on unfair contracts legislation there is an Avonside Blog post here.

Wednesday, 27 March 2013

Wastewater injection caused a 5.7 earthquake in the USA

Injection of water into the ground by the oil industry has been considered a threat to land stability by many. It is dismissed by those who benefit from the oil extraction associated with fracking, and the disposal of waste fluids by injection back into the ground.

In the USA a 2011 series of earthquakes (the maximum 5.7) in central Oklahoma have been attributed to the injection of wastewater deep underground. The wastewater was produced as a result of oil extraction in the area:

The water linked to the Prague quakes was a by product of oil extraction at one set of oil wells, and was pumped into another set of depleted oil wells targeted for waste storage.

A media release from a study involving Columbia University and the US Geological Survey has drawn attention to this connection. As the media release explains, the presence of faults near to where these processes occur are at risk of earthquakes. Part of a scientific media release is below. The full release is on the website Science News here.

The magnitude 5.7 quake near Prague (Oklahoma) was preceded by a 5.0 shock and followed by thousands of aftershocks. What made the swarm unusual is that wastewater had been pumped into abandoned oil wells nearby for 17 years without incident. In the study, researchers hypothesize that as wastewater replenished compartments once filled with oil, the pressure to keep the fluid going down had to be ratcheted up. As pressure built up, a known fault -- known to geologists as the Wilzetta fault--jumped. "When you overpressure the fault, you reduce the stress that's pinning the fault into place and that's when earthquakes happen," said study coauthor Heather Savage, a geophysicist at Columbia University's Lamont-Doherty Earth Observatory.

The amount of wastewater injected into the well was relatively small, yet it triggered a cascading series of tremors that led to the main shock, said study co-author Geoffrey Abers, also a seismologist at Lamont-Doherty. "There's something important about getting unexpectedly large earthquakes out of small systems that we have discovered here," he said. The observations mean that "the risk of humans inducing large earthquakes from even small injection activities is probably higher" than previously thought, he said.

Hours after the first magnitude 5.0 quake on Nov. 5, 2011, University of Oklahoma seismologist Katie Keranen rushed to install the first three of several dozen seismographs to record aftershocks. That night, on Nov. 6, the magnitude 5.7 main shock hit and Keranen watched as her house began to shake for what she said felt like 20 seconds. "It was clearly a significant event," said Keranen, the Geology study's lead author. "I gathered more equipment, more students, and headed to the field the next morning to deploy more stations."

Keranen's recordings of the magnitude 5.7 quake, and the aftershocks that followed, showed that the first Wilzetta fault rupture was no more than 650 feet from active injection wells and perhaps much closer, in the same sedimentary rocks, the study says. Further, wellhead records showed that after 13 years of pumping at zero to low pressure, injection pressure rose more than 10-fold from 2001 to 2006, the study says

The full release is here.

The scientific journal reference is: Katie M. Keranen, Heather M. Savage, Geoffrey A. Abers, and Elizabeth S. Cochran. Potentially induced earthquakes in Oklahoma, USA: Links between wastewater injection and the 2011 Mw 5.7 earthquake sequence. Geology, March 26, 2013 DOI: 10.1130/G33909.1


Tuesday, 26 March 2013

How our insurance policies are going to change, get more complicated, and likely to cost much more.

As this year progresses insurers are changing all existing house insurance policies from “full replacement” to “sum assured”. The change means no one will automatically have a “like for like” insurance policy.

The change will require each home owner to work out how much it would cost to replace their house, and insure it for that amount.  It won’t just be the quality of your house that affects the cost of rebuilding it, there are also factors such as the land it is on (e.g. on a slope or a hillside, access ways, retaining walls).

Replacement cost will be totally separate from rateable value or market value. If the amount you insure your house for is too little, you won’t get it rebuilt the way it was (and you might even be penalised for being underinsured). Insure for too much and you will being paying too much money and only get what you had.

Year after year the sum will need to be adjusted for increasing building costs (they never come down). Do you get the house re-valued each year, or accept the recommended increase provided by your insurance company? Get this wrong and again you may be underinsured.

The vicious underside of this new policy approach is that in a falling housing market building costs may still rise while market values decrease: your policy payments will continue to increase while the value of the house drops. Invariably cost inflation increases are far ahead of wage and salary increases, which mean insurance policies will become less and less affordable.

Against this background you can visit IAG’s brand new insurance website (here). The website is designed to help policy holders from all companies understand how the new approach will affect them.

The following is an extract from IAG’s guide to the changes which can be downloaded from the website:

What is the cost of rebuilding?

An estimate of the cost of rebuilding a home should be based on what it could cost to rebuild the house on its current site and based on its present size, standard and type of construction. It should include other structures such as decks, driveways, sheds, garages and fences.

While building costs will be a significant portion of the estimate, it should also take into account the demolition and removal of debris, site preparation, professional fees and compliance costs. The** calculator provides some allowance for these factors when estimating a home’s likely rebuilding cost.

The estimate should also include any retaining walls, Recreational Features (tennis courts, permanent swimming pools, and spa pools), and features defined in our home policy as Special Features. Check your policy wording for details about the level of cover you have (if any)

Visiting IAG’s website (here) could be very important to your financial and emotional health.

Other issues associated with the house insurance policy changes were recently blogged here.

Monday, 25 March 2013

Remembering and giving thanks for life in Avonside


You are cordially invited
to join us for the opening of a
Remembering and giving thanks for life in Avonside
Easter Sunday 31 March 2013 at 2pm
Hosted by
the Church of the Most Holy Trinity Avonside
168 Stanmore Road
Outdoor service led by Bishop Victoria Matthews
Followed by afternoon tea
Supported by
The Anglican Diocese of Christchurch
Christchurch City Council
Alexander Turnbull Library

All enquiries to the Parish office 389 6948