Canterbury Earthquake Clearinghouse

Quake city needs army of rebuilders

Above is a link to an article that touches on the many aspects of what it will take to rebuild Canterbury. The construction and engineering industries in Canterbury are experiencing a surge in demand over the past year. In addition, as a result of earthquake recovery activities, Canterbury has been experiencing the strongest growth of any region. For more information, click the above link to access the article.

In June, the New Zealand government zoned housing lands into several categories, depending on whether the land was appropriate for reconstruction. The maps for these zones can be found at the Canterbury Earthquake Recovery Authority (CERA) announcement 6430 orange zone properties turned green. Below are the 3 main categories for these zoned housing lands:

1) where repair/build process can begin (green zone)
2) where further assessment is required (orange zone)
3) where land repair will be prolonged or uneconomic (red zone)

A fourth (unzoned and mapped white) zone contains hillside and CBD land that is currently still being assessed. The orange zones have decreased as geotechnical assessments are being performed and completed. Most lands in the orange zone have been rezoned to be green. In the red zones, the New Zealand government has offered to purchase properties from land owners, and this move has been met with both eager acceptance and bitter opposition.

In the green zones, the New Zealand government has announced subdivisions into 3 technical land categories depending on what types of foundations the new housing will require:

1) TC1 – where future land damage due to liquefaction is unlikely
2) TC2 – where liquefaction could cause minor to moderate land damage in future large earthquakes; and
3) TC3 – future large earthquakes could cause moderate to significant land damage due to liquefaction.

The Guidance on house repairs and reconstruction following the Canterbury Earthquake published in December 2010 is currently under revision, and a preview summary of the updated guidance is now available on the DBH web site.

–Courtesy of Bruce Deam from the University of Canterbury

Dear Colleagues,

We are pleased to announce the posting of the GEER preliminary report on the geotechnical effects of the 2010 Darfield (New Zealand) Earthquake:

http://www.geerassociation.org/GEER_Post%20EQ%20Reports/Darfield%20New%20Zealand_2010/Cover_Darfield_2010.html

On 4 September 2010, a Mw 7.1 earthquake struck the Canterbury region on the South Island of New Zealand. The epicenter of the earthquake was located in the Darfield area about 40 km west of the Central Business District (CBD) of Christchurch. Extensive damage occurred to unreinforced masonry buildings throughout the region during the mainshock and subsequent large aftershocks. Particularly, extensive damage was inflicted to lifelines and residential houses due to widespread liquefaction and lateral spreading in areas close to major streams, rivers and wetlands throughout Christchurch and Kaiapoi. Despite the severe damage to infrastructure and residential houses, fortunately, no deaths occurred and only two injuries were reported in this earthquake. From an engineering viewpoint, one may argue that the most significant aspects of the 2010 Darfield Earthquake were geotechnical in nature, with liquefaction and lateral spreading being the principal culprits for the inflicted damage.

Many individuals participated in the GEER-NZ effort, to include three researchers from Japan. The main funding for the US contingent for the reconnaissance effort came from the NSF (via GEER), with partial support coming from PEER and EERI. The Team was led by Russell Green (Virginia Tech) and Misko Cubrinovski (University of Canterbury). Other Team members included: John Allen (TRI/Environmental, Inc.), Scott Ashford (Oregon State University), Elizabeth Bowman (University of Canterbury), Brendon Bradley (University of Canterbury), Brady Cox (University of Arkansas), Tara Hutchinson (UC San Diego), Ed Kavazanjian (Arizona State University), Rolando Orense (University of Auckland), Thomas O’Rourke (Cornell University), Mick Pender (University of Auckland), Mark Quigley (University of Canterbury), Liam Wotherspoon (University of Auckland), Thomas Algie (University of Auckland), M. Jawad Arefi (University of Canterbury), John Berrill (University of Canterbury), William Godwin (Fugro William Lettis & Associates, Inc.), Takashi Kiyota (University of Tokyo), Tam Larkin (University of Auckland), Mitsu Okamura (Ehime University), Kelly Robinson (University of Canterbury), Merrick Taylor (University of Canterbury), Hirofumi Toyota (Nagaoka University of Technology), and Thomas Wilson (University of Canterbury).

We hope that you find this GEER report on the 2010 Darfield Earthquake useful.

Russell A. Green (US-Lead) and Misko Cubrinovski (NZ-Lead)

You may view more reports and observations on our ”Reports from the field” page at http://eqclearinghouse.org/20100903-christchurch/reports-from-the-field/.

On Saturday, 9/11, I walked the Central Business District of Christchurch using prior reports of severe damage and references to retrofitted buildings as a guide. By the end of the week, 19 previously retrofitted buildings were observed in greater Christchurch and one in Lincoln. The retrofitted portions of these buildings performed quite well in comparison with similar unretrofitted buildings nearby. The retrofits ranged in age with most taking place over the last several decades. Information that may eventually become available could help clarify the criteria to which these buildings were retrofitted. In several cases, retrofits appear to have consisted only of parapet braces and wall anchors to floors and roofs. In addition, several buildings had been partially retrofitted. In some of those buildings, the unstrengthened portions suffered severe damage in sharp contrast with retrofitted portions. Access to the interiors of these buildings were generally not sought, so additional information about the retrofits and their performance from others will hopefully help our understanding. Many of the unretrofitted buildings appeared to have relatively low mortar strength and often unfilled collar joints, so gaining information about the design of retrofits of similar buildings in the vicinity will be an important benchmark of performance for regions of the world with similar strengths, configurations and hazards. A notable variety of techniques were used for retrofitting unreinforced masonry including throughbolts, screen anchors, glass fibre reinforced polymer, and the addition of external steel vertical and horizontal elements. Buckling restrained braced frames and eccentric braced frames were observed in retrofits of institutional buildings. These methods did not exhibit systematic vulnerabilities as a result of this particular sequence of earthquakes.

Many modern and relatively undamaged buildings and their occupants in older commercial districts were also indirectly impacted by the disruption caused by nearby severely damaged buildings. Falling hazards generally tended to stem from unreinforced masonry that experienced failures of unbraced parapets and inadequate between upper walls and roofs.

Glass breakage was prevalent in many midrise commercial and institutional buildings, some from the mid-20th century and newer.

Over 15,000 chimneys have been estimated by the New Zealand Earthquake Commission to have suffered severe damage. In the past, Christchurch has prohibited most uses of chimneys and have encouraged homeowners to replace the use of chimneys for heat with more efficient and less polluting sources. As a result, a significant number of homeowners had removed the tops of chimneys frome their homes prior to the earthquake.

Some wood frame buildings utilize brick masonry walls as fire separations near property lines. Incompatibility of deformations between the more flexible wood frame systems and the more rigid masonry walls caused severe damage in the walls in several buildings.

Many low-rise unreinforced masonry buildings utilized cavity wall construction with wire ties connecting wythes of brick. Severe damage due primarily to out-of-plane response and instability occurred in some of these wall systems.

Severely damaged unreinforced masonry buildings have created challenges for barricading and disruption to keep the public from being exposed to loose elements that could fall, particularly on streets and intersections with busy pedestrian and auto uses.

Reportedly only one fire occurred in the Central Business District of Christchurch when electricity was restored.

Preliminary Report on Bridge Damage from the Darfield (New Zealand) M7.1 earthquake of September 4, 2010 – Draft of 2010-09-13 by by Michel Bruneau, Myrto Anagnostopoulou, and Alessandro Palermo may be viewed here: http://eqclearinghouse.org/20100903-christchurch/reports-from-the-field/preliminary-report-on-bridge-damage-from-the-darfield-new-zealand-m7-1-earthquake-of-september-4-2010-%E2%80%93-draft-of-2010-09-13/

Here is a link to photos of nonstructural damage from the University of Canterbury:
http://www.canterbury.ac.nz/photos.shtml