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Friday, January 13, 2012

Insurance companies on possible building delays

The Press online has a great little item, New tremors delay rebuilding, repairs, based on interviews with representatives from Lumley and VERO insurance companies.

Both discuss the impact of the most recent weeks of aftershocks, and the extent to which repairs and rebuilding will be affected. Also discussed is the possibility of increased costs, the need for reassessments in some areas (repairs may be reclassified as rebuilds), and determining the areas where work can start first.

The article is here.

Thursday, January 12, 2012

CERA survey on what people want from the rebuilt city centre

CERA are conducting an on-line Christchurch Central City Commercial Property Study of what is needed for the rebuilt city centre.

From the CERA website:
CERA is undertaking an in-depth survey to find out what property and business owners, and their customers, want from the re-built city centre.  This survey is designed to capture property owners' and users' intentions so CERA can help the government and council put the draft Christchurch Central City Plan into action.
As well as seeking input from property and business owners there is also a survey for customers.

A wide range of issues are covered including where you would like to to see retail and business premises located, inner city safety, the highest level building you would be prepared to work in (and presumably be a customer in), and lots else.

The survey starts here. Give it a go.

Community Forum - meeting agenda and notes

CERA have put the agenda and notes for Community Forum meetings on their website. The notes are a bit cryptic but show that real issues are being considered. They are here.

NOTE ADDED 12 FEB 2012: At some time in the past few weeks CERA blocked access to the page with the Community Forum material mentioned above.

Wednesday, January 11, 2012

Earthquake basics - Liquefaction

While on the topic of liquefaction, the EERI (Earthquake Engineering Research Institute, California) have published a pamphlet called: LIQUEFACTION: What it is and what to do about it. A detailed and intelligible explanation of liquefaction, and the hazards it poses, is provided in eight pages of text and diagrams.

The purpose of the pamphlet is descibed as:
"... The authors hope that the information presented here conveys, to policymakers in particular, that better understanding of the risk from liquefaction at a particular site or area leads to better decisions regarding mitigation options, response planning, and preparedness strategies. With good liquefaction opportunity and susceptibility maps as a starting point, public officials and private property owners can make informed decisions about how to concentrate limited resources to manage and reduce the risk."
Another good read for anyone living in a TC3 zone (and Wellington!). The topics covered are:
  • Liquefaction Process
  • Effect of Liquefaction on the Built Environment
    • Flow Failures
    • Lateral Spreads
    • Ground Oscillation
    • Loss of Bearing Strength
    • Settlement
    • Increased Lateral Pressure on Retaining Walls
  • Can Liquefaction Be Predicted?
  • What Are the Options for Mitigation?
  • How Is the Choice of Mitigation Options Made?
  • Does Mitigation Work?
  • Is It Possible to Prepare for Liquefaction?
  • What Are the Implications for Response?
  • What Are the Implications for Recovery?
A copy can downloaded from here.

The EERI also produced, in May 2011, a special report on the effects of the February 22 earthquake. It is a very good summary of the damage that occurred, and some of the lessons to be taken out of what happened. The report can be found here.

Tuesday, January 10, 2012

The REAL Dirt on Liquefaction

Yesterday's post showed how earthquake damage to a small town could be carefully, and usefully, described. Knowing what happened is important for many reasons, and provides a context for all that follows.

That, in itself, is not sufficient to ensure that towns or cities are as safe as possible. While it is often heard that the liquefaction risk in Christchurch was well known, it seems to have been well known to only a small number of people. In addition to this limitation, hindsight also suggests there was little desire to commit to gaining more information, and ensuring it was widely available. The Earthquake Royal Commission will establish the extent to which this was true for the inner city, but no credible investigation seems likely on the same issues for urban areas.

Once again this is an issue better handled overseas. In 2001 ABAG (Association of Bay Area Governments, in the San Francisco Bay Area) published a document The REAL Dirt on Liquefaction: A Guide to the Liquefaction Hazard in Future Earthquakes Affecting the San Francisco Bay Area. Written for Bay Area residents, it sets out the hazards that arise from liquefaction, earthquake scenarios, the conditions under which liquefaction is expected to occur, the areas most likely to experience liquefaction, the damage to be expected, and what preparations can be made.

For those in a TC3 zone, Table 5 on pages 23 and 24 is of interest. It discusses techniques for liquefaction hazard mitigation, when they work best, and when the technique is probably inappropriate. A useful little checklist for whatever methods are proposed by EQC or the Department of Building and Housing.

The ABAG website is here and The REAL Dirt on Liquefaction here.

Parts of the publication don't tell Cantabrians what we don't already know. What it does do is put in one place a detailed and intelligible explanation of what has been learnt, and what can be anticipated. This is important as there is a risk that, in the name of business as usual, what has been experienced and discovered will be allowed to quietly disappear to avoid the city being seen in a bad light.

While some in the east will have long memories, many of the thousands of newcomers to Christchurch will not understand, and be oblivious to the hazards they may face if they choose to live in some parts of greater Christchurch.

Careful documentation of earthquake hazards is another area where the Council, ECan, and EQC need to be encouraged to emulate those who have done better to inform their citizens.

Monday, January 9, 2012

Describing earthquake related land damage - how the Americans do it.

The Americans, as is often the case, lead the way in sharing and explaining information. This seems to be especially so with material relating to earthquakes. In New Zealand there appears to be a mixture of reluctance to make information available, and a lack of understanding of the need for doing so.

A good example of how it could be done is a report prepared by the Unites States Geological Service (USGS) relating to earthquake damage experienced by the township of Ocean, San Luis Obispo County, California. Oceano suffered an unanticipated high level of damage as the result of a 6.5M earthquake 80km away. The major effect of the earthquake was liquefaction induced lateral spreading.

After their investigations the USGS produced a report: Liquefaction-Induced Lateral Spreading in Oceano, California, During the 2003 San Simeon Earthquake. Starting with a substantial Nontechnical Summary the report then provided detailed coverage of what happened, how, what was investigated and where, the results of the investigations, significant issues relating to the land under the town, how these produced the extent of liquefaction and lateral spread that occurred, the implications for the town in the event of future earthquakes, and a discussion on the mitigation of the hazards identified.

For a number of people this is the level of information we want. It is not necessarily too technical for non-specialists, as some skills can be acquired to make sense of what is being described. It ought not be EQC, CERA, or the government's decision whether the public can understand technical information. If written appropriately it can be understood.

The report is here.