The M 6.3 Christchurch, New Zealand, Earthquake of February 22, 2011

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EERI Special Earthquake Report — May 2011

Learning from Earthquakes The M 6.3 Christchurch, New Zealand, Earthquake of February 22, 2011

From February 22 to March 19, 2011, Technology, and the U.S. Geological deaths. Widespread liquefaction in a team organized by the Earthquake Survey. Air New Zealand generously the CBD and the eastern suburbs Engineering Research Institute provided reduced fares for EERI caused foundation movement in (EERI) and the Pacific Earthquake team members. housing and office buildings alike. Engineering Research (PEER) The publication and distribution of Two reinforced concrete office build- Center investigated the effects of this report were funded by the EERI ings and one parking garage col- the Christchurch earthquake. Led grant from NSF. lapsed, as did hundreds of unrein- by Mary Comerio, UC Berkeley, and forced masonry buildings, including Ken Elwood, University of British Introduction a number of heritage structures. Columbia, the team included Russell Many other buildings in the CBD Berkowitz, Forell/Elsesser; Michel At 12:51 pm local time on February were severely damaged, and some Bruneau, University at Buffalo; 22, 2011, an M 6.3 earthquake required demolition, which neces- James Dismuke, ARUP Australia; shook the city of Christchurch, New sitated careful controlled access to Henri Gavin, Duke University; Na- Zealand. It was an aftershock of the the CBD in the weeks following the than Gould, ABS Consulting, Inc.; M 7.1 Darfield earthquake of Sep- earthquake. The total losses are Kishor Jaiswal, U.S. Geological Sur- tember 4, 2010 (see the November estimated over NZ $20 billion. vey; Thomas Kirsch, Johns Hopkins 2010 Newsletter for a report on that Christchurch is the largest city on University; Tao Lai, AIR Worldwide; earthquake). Although lower in mag- the South Island of New Zealand, Justin Marshall, Auburn University; nitude than the earlier quake, the and the country's second-largest Ronald Mayes, Simpson Gumpertz & aftershock was centered closer to urban area. It lies within the Canter- Heger; Judith Mitrani-Reiser, Johns the city and caused significantly bury Region and has a population of Hopkins University; Troy Morgan, more damage, particularly in the 375,000. Prior to September 2010, Tokyo Institute of Technology; Tim Central Business District (CBD). Christchurch was not considered Mote, ARUP Australia; Lori Peek, While the September 4 earthquake a high-risk seismic area and had a Colorado State University; Sri struck in the middle of the night, the voluntary retrofit ordinance for its Sritharan, Iowa State University; February 22 earthquake hit when unreinforced masonry buildings. Jeannette Sutton, University of people filled the offices and cafes of That the construction types are simi- Colorado-Colorado Springs; Fred the CBD, leading to 184 confirmed lar to those of the United States and Turner, California Seismic Safety Commission; Anne Wein, U.S. Geo- logical Survey; and Mark Yashinsky, Caltrans. Tom O’Rourke of Cornell University visited Christchurch the week of April 1st with the TCLEE team and contributed to this report. Robert Fleischman of the University of Arizona also contributed. Six team members received support from the National Science Founda- tion (NSF) grant #CMMI-1132381 to focus on the specific themes of building collapse, resilience, and the use of social media in risk communication. Logistical and travel support was provided by PEER. Many other organizations also contributed travel support: ABS Consulting, AIR World- wide, ARUP, Auburn University, the Canadian Seismic Research Net- work, Forell/Elsesser, Johns Hop- Figure 1. Location of epicenter and aftershock sequence from the M 7.1 kins University, Simpson Gumpertz September 4, 2010, Darfield (Canterbury) and M 6.3 February 22, 2011, and Heger, the Tokyo Institute of Christchurch earthquakes (source: GNS).

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to 1.5g in Heathcote Valley Primary School, 1 km from the epicenter and 0.72g in the CBD. Unusually high vertical ground motions, sometimes exceeding the horizontal component, were recorded for the event. The strong ground shaking lasted for approximately eight seconds in the CBD. Ground motions recorded in the CBD generally exceeded the 500-year and even the 2500-year elastic design spectrum from the New Zealand seismic design standard (NZS 1170.5 2004). Under that standard, ordinary buildings are designed for the 500- year return period spectrum using ultimate limit states design principles, and are expected to have a small margin against collapse for the 2500- year spectrum, assumed to be 1.8 Figure 2. Horizontal spectral acceleration for Christchurch Hospital (8 km times the 500-year spectrum (King epicentral distance) from September 4 and February 22 events compared et al., 2003). Figure 2 compares the with NZS 1170.5 elastic design spectra for Christchurch (source: Elwood, elastic design spectra with the 5% ground motion data from GeoNet). damped response spectrum for the horizontal components recorded other countries, and that the earth- with the Chatham Rise extending during the September and February quake was located on an unmapped into the Pacific Ocean to the east events at the Christchurch Hospital. fault within 10km of the city center of Christchurch. The fault respon- The demands at this station are typ- make this one of the most significant sible for the February quake is not ical of the four stations located in earthquakes in recent years for code believed to be an easterly projection the CBD. The spectral demands for and standard development in the of the fault that caused the Septem- the second earthquake are clearly United States and internationally. ber quake (the Greendale fault). higher than those from the earlier The earthquakes represent reactiva- one for periods less than 1.5 seconds; for longer periods, the two Seismicity tion of faults broadly associated with regional plate deformation between events are similar. The Structural The earthquake struck on a fault ap- the Pacific and Australia plates. Engineers Society of New Zealand proximately 6km south of the Christ- Before the September 2010 earth- has recommended that the 500-year church CBD in the Port Hills at a quake, these structures were unrec- elastic design spectrum for Christ- focal depth of 5km (see Figure 1). ognized under kilometers of alluvial church be amplified by 136% for Focal mechanism solutions show deposits in the Canterbury Plains. periods less than 1.5 sec, pending further research, to address the the fault ruptured as oblique–thrust Since the September earthquake, (65° from the horizontal), dipping to increased risk of M 6-6.5 events there have been more than 18 after- close to the CBD (Hare 2011). the south. Fault slip was as much shocks greater than M 5.0, with the as 2.5m along a subsurface fault February event being the largest Geotechnical Effects rupture of about 14km. There was aftershock by a half magnitude. On no evidence of surface rupture. December 26, 2010, an M 4.9 after- The earthquake caused unprece- The earthquake extended the aftershock near the CBD caused con- dented liquefaction in the CBD and shock sequence of the M 7.1 Sep- siderable damage to unreinforced eastern suburbs as well as signifi- tember 2010 event considerably masonry buildings. cant landsliding and rock falls in the Port Hills in the southern part of eastward. The complex pattern of Strong ground motion recording aftershocks delineate a number of Christchurch. These and other geo- stations, some set up as temporary technical effects are described in east-west and northeast-southwest stations to record aftershocks from trending structures. The east-west detail in the GEER report (2011). A the September 2010 earthquake, brief summary of the geotechnical trending structures are interpreted report peak ground accelerations up to be older structures associated impacts is provided below.

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ited structural failure while leaving a near-vertical soil face intact. Con- crete and timber crib walls frequently exhibited settlement and crib cracking, but overall wall shape was preserved. Timber crib and timber pile-supported walls performed well despite deformation and ground cracking at the top of the walls (up to 450mm in one instance). Every type of retaining wall observed exhibited supported- ground failures, with the exception of timber-piled walls. Rockfall/landsliding. Many rocks fell from cliffs throughout the hill- side suburbs of Lyttelton, Mount Pleasant, and Sumner, causing a number of fatalities, damaging struc- Figure 3. Liquefaction in February 2011 (green) and September 2010 (red tures, and rendering many buildings contours) (courtesy of R. Green; GEER 2011). inaccessible due to fear of more rockfall in aftershocks. Liquefaction. Liquefaction was pavement and concrete hardscape. In some cases, entire cliffs col- widespread in the CBD and sur- Structure settlement generally affect- lapsed (Figure 5), while in others rounding suburbs (Cubrinovski and ed structures with shallow founda- boulders up to 5m in diameter were Taylor 2011), and covered a great- tions and appurtenant works, such as dislodged. Tension cracks 10-20m er area than had been indicated on planters and privacy walls. However, back from the cliff edges, often the Environment Canterbury lique- building settlement was not limited through residences, are being mon- faction hazards maps produced by to structures with shallow founda- itored. The prodigious rockfall was Environment Canterbury in 2004. tions; uplift of utility vaults and below- likely due, in part, to a number of A range of liquefaction-induced ground structures was also common. source areas having been loosened phenomena were observed, includ- in the September earthquake; fur- ing sand boils, settlement, uplift, Lateral spreading in the CBD extend- thermore, the February quake pro- and lateral spreading. The region ed on the order of 10-30m from river duced significant vertical ground affected was considerably larger banks, based on the location of ob- accelerations as well as topograph- than that of the September 2010 servable tension cracks and ground ic effects that increased ground earthquake (Figure 3), with more surface deformation patterns. The motions. than 50% of the Christchurch area largest fissures and deformations ob- affected. As much as 2-3m of later- served were on the order of up to 1m. Efforts were underway at the time al spread and 1-2m of settlement Retaining walls. A survey of about of the reconnaissance to map boul- were observed in the eastern sub- 100 retaining walls ranging in height ders, rockfall/debris travel paths, urbs. The combined settlement from 1-5+m was caused by liquefaction during the conducted in recent earthquakes and aftershocks areas of Lyttelton, has exposed many Christchurch Mount Pleasant neighborhoods to increased threats and Sumner. The from river and ocean flooding, in- survey was not cluding tsunami. exhaustive, and Sand boils were the most common was limited to evidence of liquefaction, and in walls that could many locations sand and silt tens be observed from of centimeters thick accumulated in public right-of- lower-lying areas and filled drain- ways. Many walls, ages (Figure 4). Sand boils were especially brittle frequently accompanied by defor- ones such as mation and settlement of flexible grouted rock and masonry, exhib- Figure 4. Severe liquefaction in the CBD (photo: Kam)

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ylene (HDPE) pipelines after the September earthquake, and there was not a single instance of damage in that system, although Lyttelton had some of the strongest ground motion recorded in the earthquake, and massive liquefaction was observed in Harwood, including lateral spreading and settlements of 1- 2m. Moreover, there was no damage in the medium-density polyethylene (MDPE) gas distribution system, even though the MDPE pipelines were located in areas subjected to liquefaction during both earthquakes. Bridges. Most bridges in the Christ- church area are short spans of regular configuration and sometimes monolithic or well-restrained; these bridges generally performed well during the earthquake. Although Figure 5. Large and damaging rockfall behind Moa Cave Guest house, Red- there were no bridge collapses, cliffs (photo: Mote). damage observed in specific types and rockfall source areas. Where tions with the vaults. Approximately of bridges provides insight into their rock fall was still considered pos- 1m of settlement at the Bexley behavior under large lateral spread- sible in aftershocks, potential haz- Pump Station ruptured the well, ing and ground motion. ards were being scaled away with which flooded the surrounding The Anzac Drive Bridge, constructed 3 temporary rockfall retaining barriers neighborhood at 140m /hr. Mas- in 2000, was composed of precast setup to protect the public. Con- sive amounts silt and sand from girders (as are most bridges in New siderable coordination among the liquefaction washed into the Bexley Zealand) and a precast substructure. geotechnical inspections, structural sewage treatment plant, damaging Much of the damage (e.g., cracking inspections, and water infrastruc- the primary settling tanks and over- of bent cap) was likely due to lateral ture surveys was required. loading the system. Liquefaction spreading. also caused differential settlement Damage to recently retrofitted Lifelines and Transportation of the clarifiers, thereby seriously impairing secondary treatment bridges (on Port Hills Road and Lifelines. There was extensive capabilities. Horotane Road) was generally of damage to lifelines, including pota- slight consequence, consisting of ble water, wastewater, and drainage The impact on the electric power abutment wall failures, rotation of facilities, roads and highways, and distribution network was approxi- abutments, and pile cracking—all electric power distribution. The dam- mately ten times that of the Sep- accompanied by lateral spreading. age was caused predominantly by tember earthquake in terms of With a few exceptions, the bridges liquefaction; differential settlement service disruption and damage to were reopened to traffic as soon as and lateral spreading disrupted both facilities. The electric power admin- new ramps could be filled in over the potable water pipelines (mostly as- istration buildings were badly dam- settled approaches. A notable ex- bestos cement and PVC) and waste- aged. All major 66 kV underground ception was the Moorhouse Road water pipelines (mostly gasketed cables supplying the Dallington and Bridge, which had severe shear-flex- concrete and PVC). There are likely Brighton areas of eastern Christ- ural damage to some of its columns, thousands of breaks and lesser church failed. Over 50% of all 66 due to poor reinforcing details. That flaws in these networks, and the kV cables at multiple locations were bridge remained closed for five weeks total number of required repairs is damaged by liquefaction-induced after the earthquake while tempo- still unknown. Buoyancy of concrete ground movement. rary steps were taken to prop up the vaults at potable water and waste- The water distribution network in deck. water pump stations, compounded Lyttelton and Harwood had been Several bridges (Bridge St Bridge, by liquefaction-induced settlement, replaced with high-density polyeth- Fitzgerald St Bridge) exhibited flex- caused pipes to break at connec-

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lapsed; others partially collapsed. vertical differential settlement that At the same time, several modern tilted buildings. Foundation types buildings performed well (see the also varied in the CBD, ranging from Tagging section for approximate shallow foundations to deep foun- statistics). Though such variations dations with equal or unequal pile in performance can be attributed to lengths and, in some cases, mix- material type, year of construction, tures of shallow and deep founda- and differences in structural layouts, tions. Figure 6 shows the tilting of the variation in soil conditions and two adjacent buildings: the build- shaking (measured peak ground ing in the foreground was said to acceleration within the CBD varied be on a shallow foundation, while from 0.36-0.72g) throughout the city the building in the background was no doubt also played a role. Signifi- reported to be on a combination of cant liquefaction adjacent to some piles and structures led to several inches of

Figure 6. Differential movement of adjacent buildings (approximately 700mm at roof level) due to foundation rotation (photo: Elwood). ural cracking of piles due to liquefaction and lateral spreading of the surrounding soil. There may have been similar cracking in piles supporting wall-piers, but those were hidden from inspection.

Utilities carried by bridges (Bridge Figure 7. Collapsed reinforced concrete buildings: (a)  The CTV Building Street, Fitzgerald Street) were fre- and core wall (photos: Kam, Berkowitz); (b) ▼ The PGC Building (photo: quently damaged. In some instances, Elwood). sewer lines spilled their effluent into the river or water mains broke and washed out embankments. In other cases, the high relative stiffness of the utilities damaged the bridge.

Buildings Reinforced concrete and masonry buildings. Most of the buildings over four stories in the city of Christ- church are either reinforced concrete or reinforced masonry, and are generally concentrated in the CBD. Multi-story steel buildings are noticeably scarce, mainly because industrial relations issues associated with site welding have significantly hindered steel construction in New Zealand since the early 1980s. Some reinforced concrete and masonry structures completely col-

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Figure 9. A permanent twist and residual lateral displacement in the 19-story Hotel Grand Chancellor (photos: Elwood, Comerio). Figure 8. Punching shear failures in parking garage (photo: Berkowitz). adjacent laneway by the means of aged wall was stabilized within a transfer girders located on the sev- week of the earthquake, but the shallow foundation. Both buildings enth story, and out-of-plane shear building is now set for demolition. are expected to be demolished. failure was observed at the base of That significant damage to critical the wall providing the prop for the elements was visible in a number of Two reinforced concrete office build- southernmost transfer girders. Three ings collapsed (Figure 7): the Can- buildings is notable, since the quake columns in the same grid line as the was short in duration with relatively terbury Television (CTV) Building, transfer girders on the sixth story which caused approximately half the few cycles of strong motion. This also exhibited shear and axial fail- damage (Figures 10 and 11) was fatalities in the quake, and the Pyne ures. The building was surveyed for Gould Cooperation (PGC) Building, found in older as well as modern several days following the earth- buildings, but was more prevalent where 12 people perished. The six- quake and the lateral displacement story reinforced concrete CTV build- in buildings constructed before the was not found to be increasing de- mid-1980s, when capacity design ing was designed in the mid-1980s spite many aftershocks. The dam- and consisted of a coupled shear wall on the south side and a core wall on the north side of the building. The entire building, with the exception of the core wall, collapsed (Figure 7a). The PGC building, designed and built in the early 1960s, was a five-story reinforced concrete frame building with a core wall offset towards the rear of the building. The top four stories collapsed onto (a) (b) the intact first story, with some floor slabs appearing to detach from the core wall (Figure 7b). Punching shear failures of a pre- stressed floor slab resulted in partial collapse of a concrete parking garage at the south edge of the CBD (Figure 8). After the earthquake, a permanent twist and residual lateral displacement could be observed in (c) the 19-story Hotel Grand Chancellor, (d) one of the tallest buildings in Christ- Figure 10. Examples of damage in concrete buildings: (a) column shear church (Figure 9). The east side of failure, (b) precast wall damage, (c) beam-column joint, (d) wall damage the building cantilevered over an (photos: Sritharan).

6 EERI Special Earthquake Report — May 2011 approaches were introduced in New sitating demolition. Typical damage direction, unbonded post-tensioned Zealand. Common observations included shear failure of walls and rocking wall in the other) remained included 1) irregular configuration of failure of walls and columns due operational with little or no damage. lateral load-resisting systems in plan to poor grouting of reinforcement Steel buildings. Most of the steel and/or elevation, 2) non-seismic within the masonry cells (Figure 12). buildings in the areas of severe detailing in the gravity system, and Precast concrete construction is shaking are of recent vintage, de- 3) poor grouting of reinforcement used extensively for the buildings signed to the latest seismic provi- in reinforced masonry buildings. In in and around Christchurch and sions, and generally performed well. general, significant liquefaction was includes 1) emulative precast mo- The Pacific Residential Tower in not observed adjacent to the build- ment frames for multi-story struc- the CBD (22 stories, completed in ings with these structural damages. tures; 2) topped precast flooring 2010) and the Club Tower building Reinforced concrete moment frame elements for multi-story structures (11 stories, completed in 2009) had buildings, constructed since the mid- and carparks; 3) precast cladding eccentrically braced frames (EBFs) 1980s, generally performed well and panels; and 4) precast stair ele- for which evidence of inelastic de- exhibited limited beam hinging and ments. With the exception of the formation was limited to flaking of undamaged beam-column joints. precast stairs, the vast majority of the brittle intumescent paint on the Reinforced concrete shear wall these elements and systems per- EBF links at some levels. Both were buildings also generally performed formed as intended. Emulative green-tagged following the earth- well. Exceptions to this good per- frames developed beam end plastic quake, requiring only some minor re- formance included the compression hinging to a level of damage com- pairs of nonstructural components. buckling of a wall and fracture of mensurate with the seismic excita- In a low-rise parking garage, a few longitudinal bars in a wall boundary tion; floor systems remained seated EBFs developed lower flange frac- zone (Figure 10d). Figure 11 shows and intact, with damage limited in tures, with cracking propagating into what appears to be a regular build- most cases to displacement com- the link webs; with more than six ing with two V-shaped concrete patibility cracks along the units, bays of EBFs in each principal walls on either side of it. The wall on though cracking in the end regions direction, the building survived in the south side of the building sur- of flange-hung double tees was spite of the fractures. In other build- rounds the elevator and stairs, while observed and requires closer atten- ings, fractures were observed in the wall on the north side has a di- tion; and precast cladding panels connections of concentrically braced rect connection to the diaphragm. It generally remained attached, with frames unable to develop the brace appears the north wall acted as an only two exceptions noted. Precast gross-section yield strength, and L-shaped section with a large ten- stair elements collapsed in at least multiple industrial steel storage sion flange contributing to buckling three multi-story buildings in the racks collapsed. Bruneau et al. of the unsupported web. CBD (Figure 13), trapping occu- (2011) provides a full report on per- Reinforced masonry buildings are pants in the buildings for several formance of steel structures. widespread in Christchurch, and hours after the earthquake. A hospital building with a self-centering Base isolation. The Christchurch some performed well, while others Women's Hospital, completed in were damaged to an extent neces- jointed "PRESSS" system (unbonded post-tensioned frame in one 2005, is the only base-isolated

Figure 11. Damaged wall with good reinforcement details (photos: Sritharan, Elwood).

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less than half of what would be expected given nearby recorded ground motions. This could be ex- plained by evidence of nonstructural elements (crushed macadam, buckled moat covers) binding the motion of the isolation system, and of liquefaction ejecta within the isolation galley. Hospital staff noted fewer reports of nonstructural damage in the isolated women's hospital than in the adjacent fixed-base hospitals in the complex. Industrial buildings. Most of these structures consisted of steel roof framing with three types of lateral systems: load-bearing tilt-up panels, pre-engineered steel frames with concrete cladding panels, and pre- engineered steel frames with light gauge corrugated steel sheathing. Figure 12. Examples of reinforced masonry damage in multi-story buildings A few examples of the latter were (photos: Jaiswal and Sritharan). encountered and showed no out- building on the South Island. Its ponents at the seismic gaps and ward signs of damage. 420mm isolator displacement cap- minor cracking of partitions around Several load-bearing tilt-up build- acity and its superstructure ductility window openings. The peak isola- ings required temporary shoring. capacity of 1.8 correspond to 2000- tor displacements were estimated In at least one case, the building year return-period demands. Be- at 80mm-100mm, with a northward had been stabilized but was due to cause the structure is not instrument- residual displacement of about be deconstructed. At its northeast ed, estimates of seismic responses 25mm. Peak isolator demands for corner, the roof beam-panel connec- must be inferred from observations the February quake were estimated tion had pulled out and the panel top of soil displaced by sliding moat from soil displaced by the moat moved out-of-plane approximately covers, residual displacements in covers to be about 120mm, with the isolation system, and first-hand residual displace- accounts. Observations after the ment close to zero. September quake revealed damage These isolator dis- only to sacrificial nonstructural com- placements are

(a) (b)

Figure 14. Damage to industrial buildings at steel-to- concrete connections: a) roof beam-panel connection in load-bearing tilt-up building; b) steel frame-panel con- Figure 13. Collapsed precast concrete stairs in multi-story nection in building with nonload-bearing concrete panels building (photo: Carri). (photo: Marshall).

8 EERI Special Earthquake Report — May 2011 one foot (Figure 14a); note the ab- with a target of 67% of the design wall anchorage systems were in sence of a continuous ledger at the forces required by the code for new common use: through-bolts, adhe- diaphragm to concrete panel con- construction. But Christchurch also sives, and wedge anchors. Most nection. On the west wall, the panels continued to allow retrofits to 33 % buildings were brick or stone and in had cracked near midspan and de- of code as a minimum. many cases included terra cotta and flected outward six inches. In September, the EERI team worked concrete elements. Some retrofits In several buildings with steel with colleagues in New Zealand to were done in conjunction with frames and concrete precast panels, identify previously retrofitted URM vertical additions or new buildings flexibility of the steel frame relative buildings and document their perfor- constructed behind URM façades. to the concrete panels likely resulted mance. These buildings were revis- Retrofits in many cases included in failure of the connection between ited after the February aftershock, stabilizing terra cotta ornaments, the frame and precast panels (Fig- and additional retrofitted buildings cornices, chimneys and other ure 14b). In one case, 12 wall pan- were identified (see Figure 15). The appendages. els dropped from a single ware- 57 URM buildings now thought to Most retrofitted URMs likely experi- house. Typically, the end wall panels have been completely or nearly enced ground motions well in ex- cracked because they were stiffer completely retrofitted represent cess of design motions, and in some than the steel frame. 7-12% of the URM building stock in cases, higher-than-maximum-con- the region of significant shaking in sidered earthquake motions, and URM buildings. Hundreds of unreinforced masonry (URM) buildings February. their performances varied widely: were heavily damaged or collapsed, Retrofits ranged in age from the 70% were red-tagged or cordoned roughly two to three times the num- early 1900’s to 2010, with most to prevent public entry, 21% were ber similarly damaged in the Sep- performed since 1968. The great yellow-tagged, and 9% were green- tember quake. Dozens of URM majority of the URM retrofits com- tagged. In many cases, prior dam- buildings, which were green-tagged plied with 33% of standards for new age in the September earthquake with minor or no obvious damage construction, although a notable few and the many subsequent after- in September, partially collapsed met higher criteria. A wide variety of shocks affected performance in in February. The number of deaths retrofit techniques were used, in- February. Bond failures between in URM buildings was probably cluding (in an approximate ranking anchor adhesives and masonry reduced because a number of the of most to less frequent) concrete were prevalent (Figure 16), and low buildings had been closed or cor- and steel moment frames, concrete strength mortars also contributed to doned off since September. and reinforced masonry walls, and anchor failures. Many retrofitted URM buildings were steel braces. Three major types of affected by the two earthquakes, and provide a tremendous opportunity to learn about their performance over a range of motions. Since New Zealand’s building stock, earthquake engineering practices, and retrofit approaches are quite similar to those in the U.S. and other countries, this sequence of events and the docu- mentation of performance will greatly influence practice internationally. Laws in New Zealand since 1968 required that local governments estab- lish policies for retrofits of earthquake-prone buildings, including URMs. Because Christchurch was thought to be in a moderate seismic region (before September 2010), it had a passive policy that triggered retrofits only during major alterations. After the September earthquake, Figure 15. The EERI Team studies the performance of this heavily damaged, Christchurch strengthened its policy retrofitted URM building that pounded against the building on the left and to require retrofits within 30 years partially collapsed (photo: Turner).

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Figure 16. This adhesive anchor at a URM parapet connection pulled out. A wire screen with white adhesive around the threaded rod had been inserted into a hole in the brick (photo: Turner).

Notwithstanding the failures, how- observed with ever, damage was generally sig- substantial non- Figure 17. Equipment weighing 25,000 lbs moved nificantly lower in retrofitted URMs structural damage approximately one meter (worker’s foot indicates the than in nearby unretrofitted URMs. to critical equip- original position of the equipment) (photo: Marshall). Select heritage buildings that had ment and support- been retrofitted to a high standard ing infrastructure. At one location, covering those who perished. Sec- performed well. high vertical and horizontal accelera- ond, city and volunteer engineers tions moved 25,000-pound machin- conducted level 1 (exterior) inspec- Nonstructural components. In the tions for tagging, followed by level CBD, nonstructural damage following equipment about one meter from the original position, as shown 2 (interior) inspections to assess ing the February aftershock was falling and collapse hazards that similar in many respects to the dam- in Figure 17. Workers at the facility described seeing the large equip- could result from future aftershocks age observed after the September or instability. earthquake. In office buildings and ment literally “bounce” across the retail shops, there was typically floor. At a nearby textile facility, pre- Inspectors cordoned off 114 square damage to ceiling grids with lay-in cision equipment was damaged by blocks initially, but reduced the closed light fixtures, overturned shelving, the ground motion; the misaligned area to 75 blocks ten days later. The broken sprinkler pipes, and broken equipment would have caused short- area has approximately 200 con- furniture and contents. Numerous term production disruptions, but wide- crete and 500-600 masonry buildings. facades of more modern structures, spread liquefaction damaged the About 50% of all the buildings are often comprised of glass and light- factory floor slabs and put the facility unusable because they sustained weight metal panels, were damaged out of business for an undetermined significant damage or because they and on occasion fell to the sidewalk, period of time. As was the case in are adjacent to hazardous buildings. September, numerous storage rack threatening not only exiting occu- Before the cordoned area can be re- collapsed in warehouses (Figure 18), pants, but also search and rescue duced, the city must stabilize some necessitating the disposal of dam- and inspection teams. A notable buildings slated for demolition to aged goods. success story was found at a major prevent building parts from falling telecom building that had started Community Impacts into the streets or onto adjacent a ceiling retrofit program after the buildings. In addition, the city prefers September earthquake, which in- Central Business District (CBD). to conduct demolitions while streets cluded additional restraint for the The earthquake devastated Christ- are still closed. The city began ceiling grid and independent re- church’s CBD. During the emergen- allowing brief access to green and straint of lay-in light fixtures. It was cy response period, questions about yellow-tagged buildings on a block- completed shortly before the Febru- safety and access affected building by-block basis three weeks after the ary quake, and ceiling damage was inspections and decisions on recov- earthquake, but the cordon was still noticeably reduced relative to simi- ery. in place two months post-event. lar buildings in the area. First, the Urban Search and Rescue The “critical buildings project” was East of the CBD, in an industrial area (USAR) teams rescued people who established immediately after the closer to the February epicenter, were trapped, and then continued earthquake to address heavily dam- several manufacturing facilities were with the hard job of finding and re- aged buildings over approximately

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the CDC and CECC are aimed at generating economic assistance for recovery and promoting sustain- able employment opportunities in a renewed business district. Looking forward, the planners see increased village centers in subur- ban areas, and a CBD with low-rise development focused on educational institutions, hospitality, high-end retail and residential projects, and green space along the river. As plans evolve, the mayor and city council will listen to a variety of interest groups, but thus far all seem to want to take care of dangerous buildings quickly, set clear rules for planning, zoning, and building codes, estab- lish tax or other investment incen- tives, restore symbolic buildings such as the cathedral, rebuild and/or reopen public institutions (city council, Figure 18. Collapse of storage racks (photo: Elwood). museums, schools), and invest in six stories that were considered criti- erty owners will reinvest in Christ- public infrastructure (sidewalks, cal to the reopening of the CBD. Led church. Among the concerns are streets, services) so that businesses by top engineers from the Depart- a) potential for financial flight, can repair and rebuild. ment of Buildings and Housing, the b) fear of returning to the CBD, and Schools. The earthquake closed project assessed the stability of the c) intransigence on the part of indi- 419 early childhood education buildings and provided advice on vidual property owners. However, centers (ECEs), 215 primary and what action the city should take to 120 CEOs of Christchurch-based secondary schools in the Selwyn, reduce hazards from approximately companies have come together to Waimakariri, and Christchurch City 40 buildings. In some cases, tem- plan for the future of the CBD. school districts, and leading tertiary porary stabilization methods were In addition, the Canterbury Devel- institutions including Canterbury proposed. The project engaged both opment Corporation (CDC), which and Lincoln Universities. Dozens of local and international experts in the combined forces with the Canter- post-secondary Asian students died evaluations. bury Employer’s Chamber of Com- in the collapse of an office building There were about 6,000 companies merce (CECC) after the September in the CBD that housed an English and/or institutions with over 50,000 earthquake, is planning for both language school, but there were employees in the CBD, or 25% of near-term business survival and no other reported fatalities among the total employment in the city. Of long-term revitalization. About school-age children. the 50,000 employees, 45% are in NZ$10 million was made available Out of 161 school damage assess- government, health care, or profes- to the business community after the ments, there was minor damage to sions; these workers are likely to September earthquake, and there 107 schools (affecting 31,074 stu- retain their jobs in another location. will be another NZ$200 million after dents), medium damage to 35 (af- The other employees are in a the February event. These funds fecting 15,423 students), and major variety of sectors including hotels, include government support of damage to 19 (affecting 9,695 stu- restaurants, retail, manufacturing, NZ$500 per employee per week for dents). Lack of water and wastewa- construction, wholesale, transport, 12 weeks, as well as a “business ter services prevented school re- communication, finance, insurance, trust fund” for direct business-to- opening for 70,000 students across and recreation; many in this group, business support for relocation, IT, the three districts one week after especially those in tourism, will be marketing, and other needs. These the event. Subsequently, over 8,000 unemployed. funds will help keep cash flowing students re-enrolled in schools in the community, supporting those The businesses were well insured, throughout New Zealand. On March who are out of work and helping so there will be capital for rebuilding, 8, the New Zealand government some businesses to restart. Over but there is no guarantee that prop- passed an Order in Council to help the longer term, the joint efforts of

11 EERI Special Earthquake Report — May 2011

Figure 19. Classroom tents in the car park of the University Figure 20. Temporary water tanks in front of Christ- of Canterbury, March 14, 2011 (photo: Comerio). church Hospital (photo: Gavin).

speed the recovery process of the school, and online instruction. The a six-story concrete shear wall build- school system. The order enabled secondary and tertiary education ing from circa 1931, was extensive- the Minister of Education and Sec- sectors will be economically affected ly damaged and will likely be de- retary for Education to (a) tempo- by the flight of fee-paying internation- molished; the building had been rarily change school enrollment al students and the decrease of unoccupied since the September schemes without community consul- international student recruitment. earthquake. tation; (b) change the definition of Hospital. The Christchurch Hospi- Housing and insurance. Most a "half day" so schools could share tal—the South Island’s largest terti- dwellings in the Christchurch region sites; and (c) ensure students could ary hospital with 600-650 beds— are one-story, an average of 150 m2, return to their home school if and suffered little structural damage, but and are built of light timber framing when it reopened. had to evacuate 160 patients and on concrete slab or pile foundations On March 14, Christchurch City request support from other facilities in accordance with NZS 3604 (first schools began to reopen, and stu- to cover functions such as laundry published in 1978). A common roof- dents arrived armed with bottles of service. The hospital’s backup power ing material is light metal coated boiled water. Nine learning hubs generators failed due to sludge clog- with stone chips. Timber weather- were established to replace closed ging the filters, forcing patients to be board, plastered stucco or unrein- primary schools. Four closed high evacuated from the main ward. The forced brick veneer is used for ex- schools shared sites with four open hospital also had to move patients terior cladding. The veneers are high schools. As of March 21, 97% from the fourth and fifth levels of anchored through small steel ties of school sites were reopened, but the Riverside building due to leaks every two feet horizontally and one only 600 of the 8,000 students who caused by sprinkler damage. Pipe foot vertically that are embedded in had left the districts had returned. failures were also discovered in the mortar between bricks and screwed The Order in Council also enabled sewage system. Ceiling damage to a stud on the other end. ECE centers to relocate and/or was prevalent in older buildings with Overall, houses in Christchurch are operate in restricted spaces, such heavy plaster tiles, while lightweight maintained well; according to a that 76% of ECE services had ceilings performed well. The hospital 2005 report, more than 80% were reopened by March 21. was also suffering from a lack of deemed to be in nearly new condi- water pressure due to liquefaction The University of Canterbury (UC) tion and only about 3% required damage to the tunnel housing pipes progressively reopened within 3-4 some sort of immediate attention. that carry steam from the boilers weeks of the earthquake while prom- Their average valuation is about across the street to the hospital; ising to deliver a high-quality, full NZ$300,000, including land (Clark as a precaution, the hospital has academic year program of teaching et al. 2005; Beattie and Thurston brought in storage tanks with almost and offering grants to compensate 2006). The earthquake shaking 53,000 gallons of water (Figure 20). students. Across all educational in- caused only limited structural dam- There were several instances of stitutions, alternative classroom age to dwellings, but nonstructural mechanical equipment jumping off capacity was created with tempo- damage was widespread. Chimney mounts, as well as overturned furni- rary classrooms (Figure 19), off-site failure, brick fence collapse, and ture. One building on the hospital’s venues, site sharing, correspondence plasterboard cracks are common in campus, the Hagley Nurses Hostel, virtually all earthquakes of this mag-

12 EERI Special Earthquake Report — May 2011 nitude, and account for significant dollar losses. As was the case in the September earthquake, soil liquefaction and/or lateral spreading caused most major structural damage to thousands of dwellings, particularly those situated along the banks of the Avon River and in the eastern coastal suburbs (Figure 21). Precise counts of housing damage are still underway, but government sources have reported that as many as 10,000 homes are likely to be demolished, and that some of the land area is beyond repair and will have to be abandoned. On April 4, 2011, New Zealand’s Earthquake Commission (EQC) reported 99,042 claims generated by 90% of communities assessed. While the total number of claims may be comparable to the Septem- Figure 21. A house in Kaiapoi moved on its foundation in both the Septem- ber earthquake, the total economic ber and February earthquakes a total of 1.8m (photo: Lai). loss will exceed that of the previous event. (volunteers), police forces, military crushed parked cars. Precast stair- personnel, and disaster victim identi- case collapses typically had low The EQC was established in 1945 fication teams (DVI). void-space potential, but in some to protect residents against the fin- cases large voids were found. None- ancial impacts of natural catastro- The New Zealand government’s logistical support for urban search theless, the probability of surviving phes. The current EQC insurance the collapse of a precast staircase is policy was regulated in the mid- and rescue operations was robust, and typical logistical challenges low due to the height of fall (typ- 1990s and has remained unchanged ically several stories) and the V- since then. It costs homeowners a were not an issue. Heavy equipment, construction materials, and shaped wedging collapse pattern small fraction of the sum insured, exhibited (see Figure 13). and provides protection of up to technical expertise were readily NZ$100,000 for a dwelling (build- available at a moment’s notice. Res- Typically, USAR teams in the U.S. ing), NZ$20,000 for contents, and cue operations were concentrated in deploy with three structural special- an amount for the land on which the the CBD, where most of the col- ists, but in this earthquake the U.S. dwelling is situated. When the actual lapsed and damaged structures team included five structural spe- damage is beyond the EQC limit, were URM or concrete; in addition, cialists. This depth of technical ex- homeowners must rely on private buildings shored after the Septem- pertise allowed USAID to provide insurance or personal funds. ber earthquake also collapsed and engineering support to other inter- some buildings under repair suffered national teams that normally do not Emergency Response further damage. Previous earth- include structural specialists. These quake damage was a consideration specialists provided engineering Search and rescue. An internation- in every USAR operation. recommendations during searches, al effort of more than 600 urban Void spaces observed in collapsed demolition surveys, and de-layering search and rescue (USAR) person- structures varied in size and config- operations. nel assisted with search and rescue uration. Unreinforced brick masonry Although USAR operations do not immediately after the earthquake. typically had low void potential and typically become involved in opera- Teams came from Japan, China, survivable spaces. Concrete floor tions involving building demolition Australia, Singapore, Taiwan, and systems typically remained intact identification, the U.S. team was the United States. The New Zea- and provided more viable and sur- able to provide the New Zealand land government also deployed vivable void spaces. Void spaces government this service. This differs three New Zealand USAR Task in parking structures were typically from practice in the United States, Forces, numerous volunteer fire large and viable due to the “verti- where this task would typically have departments, civil defense teams cal support” provided by partially

13 EERI Special Earthquake Report — May 2011

been assigned to the local public approximate breakdown of tagging updates. Those with access to the works/building department. by building type, based on March 18 Internet could get official and unof- data. ficial information online. Several Building safety assessments/ telephone helplines were estab- tagging. New Zealand uses building safety assessment procedures Social and Economic lished to assist affected populations, very similar to those in the U.S., Impacts for example, a 24-hour, seven-day- where green (inspected), yellow a-week Canterbury Earthquake Social science research mora- Government helpline for those (restricted use), and red (unsafe) torium. On February 23, 2011, the placards indicate approved access seeking information or emergency day following the earthquake, New financial support, and a Quake to damaged buildings (NZSEE Zealand Civil Defence declared a 2009; ATC 1995). Some buildings Support and Counseling helpline. state of national emergency. Soon Recovery Assistance Centres and undamaged in September that had thereafter, the national controller received a green-tag collapsed Work and Income Service Centres placed a moratorium on social sci- were opened throughout Canterbury. and caused casualties during the ence research until May 1, 2011, in February aftershock. Christchurch Special support was also offered for order to protect survivors from addi- migrants and refugees, for families instituted several enhancements to tional burdens and to ensure that the tagging process in February that with children, school teachers, and vital resources were directed toward for survivors of domestic violence. could be adapted for the U.S. For emergency response only. example, reinspection of buildings Just days after the earthquake, the following aftershocks was controlled In this challenging situation, one Christchurch City Council integrated by the response of eight “indicator” team member traveled to Wellington social media into their communica- buildings specifically selected to be to meet with disaster researchers tion strategies. The Council had not representative of common structural and to discuss fieldwork objectives. used social media following the systems. Indicator buildings were After consulting with New Zealand September earthquake, but moved inspected following aftershocks for researchers, the EERI social scien- rapidly in February to incorporate a further damage that would trigger tists agreed to listen and observe, new blog, Twitter feed, and Face- reinspections. but not to launch any formal re- book page. Council staff monitored search efforts. During inspections, a blue hazard public chatter online to identify un- assessment form for red-tagged Risk communication channels met needs within the community, buildings was completed by the and strategies. Widespread power posted updated information via chartered professional engineer outages followed the earthquake Twitter and Facebook, and respond- and sent to the national controller and remained primary issues for ed to all requests for information that to be used in determining whether thousands of residents for weeks. were posted on their fan pages or immediate demolition was required. Water treatment plants and sewage in response to messages on Twitter. Assessment team safety was main- systems were heavily damaged, The University of Canterbury, which tained by requiring teams to send requiring rapid communication strat- enrolled more than 20,000 students a text message to the EOC at 90- egies regarding public health and before the earthquake, followed minute intervals. Each inspection safety issues. The modes of com- a similar protocol in monitoring its team had two USAR personnel to municating to ensure safety while traversing the affected house- CBD and entering potentially unsafe holds and busi- buildings. Rapid Response teams nesses includ- were “on-call” to respond when ed door-to-door building owners needed more de- pamphleting tailed structural inspections, evalu- and posts to ation of falling hazard cordoned community areas, and tenant escorts to retrieve bulletin boards contents in damaged buildings. and in other public spaces. As of April 15, more than 60,000 Print and total assessments have been broadcast accomplished, with the following media outlets, breakdown of red tagged buildings: briefed daily 1788 residential buildings, 1109 by government Building Assessments in Central Business buildings within the CBD, including officials, pro- Figure 22. District (Kam et al. 2011, Data source: Christchurch City 395 heritage buildings (Civil De- vided regular fence 2011). Figure 22 shows the Council)

14 EERI Special Earthquake Report — May 2011

Facebook page and responding delivering informational pamphlets deformations have left the areas directly to student concerns and to those directly affected by the prone to flooding. With peak ground requests for additional information. earthquake. Many elderly residents accelerations exceeding 0.5g, the Unofficial social media presence called on the SVA for help with re- February quake caused collapse in was also significant, led by a virtual moving debris, as did government many URM buildings, some of them network of online volunteers who officials who needed assistance retrofitted. Data from this event created and staffed the Christ- with various tasks. Social media will help us understand the poor church Recovery Map site. This were also used for finding missing performance of some retrofitted group—whose work was driven by persons and as an outlet for remem- URM buildings and develop better a determination to get people the brance and expressing grief for the design approaches and standards. information they needed as quickly deceased. There is a window of opportunity as possible—posted the first acces- Risk messaging. Communicating with the ongoing revisions to ASCE sible maps, via Google, of the CBD risk and uncertainty in the aftermath 31/41 guidelines to incorporate and outlying areas. Major print and of the February earthquake was a these important lessons. Similarly, online media sources in the Christ- high priority for public officials faced the extensive damage to concrete church area then reproduced and with reassuring the population that buildings, despite the very short published the maps. effective measures were in place to duration of the earthquake, holds important lessons for understanding Because of the destruction in the restore infrastructure and protect lives. The importance of these ef- collapse mechanisms and improv- CBD and the focus on life-saving ing seismic assessment techniques. activities among emergency re- forts was amplified by the back-to- back earthquakes over a six-month Earthquake engineers from around sponders, technology volunteers the world have extraordinary op- launched online resources more period and ongoing aftershocks, all of which elevated anxiety and con- portunities to collaborate in both quickly than the official responders academic- and practice-oriented were able to, providing early access cerns about safety. By mid-March, it was estimated that tens of thou- research on building performance, to curated information to those who soil-structure interaction, impacts could get online. The virtual volun- sands of residents were still displaced. Government officials were of liquefaction and lateral spread- teer team stopped its efforts once ing, consideration of aftershocks normal communication channels unsure when, if ever, these individ- uals would return and were in the in design and post-earthquake resumed and directed prior users to assessments, and other key topics. visit the official government site at process of developing a strategy http://canterburyearthquake.org.nz/. for communicating with displaced With reference to post-earthquake Rather than leading to “information residents. safety assessment, it was clearly overload” from competing sources, Risk perception and the impact on demonstrated that, when large the spontaneous and official online international tourism, which accounts numbers of buildings are damaged resources performed complemen- for 9% of the nation’s GDP, was also and a large portion of the city is tary functions at different points in a major concern among officials. closed, it becomes critical to have the response and early phases of Those who had returned to Canter- access to drawings. This earth- recovery. bury expressed fear of re-entering quake emphasizes the need for tall buildings, and there was some cities to create a centralized and Online channels for organizing. accessible database of structural Social media and online channels misinterpretation of risk regarding the various colored placards that drawings for use in emergency used to communicate risk and assist building evaluation. with the response were instrumen- were placed on damaged buildings. tal in organizing volunteers and do- As of April 30, 2011, the state of na- On the policy side, the New Zea- nations. Many small-scale efforts tional emergency was still in place, land earthquakes can provide val- emerged in the wake of the earth- and it will likely continue for several uable lessons to those areas of the quake, but the Student Volunteer more weeks. Thus, many outstand- U.S. where there is either lower Army (SVA), which mobilized more ing questions still remain regarding seismicity or infrequent, high-con- than 12,000 spontaneous volunteers communicating current and future sequence events. Some of these (about 90% of whom were university risk for residents. areas use “relaxed” or reduced students), stands out. Using a Face- seismic criteria even today and book page, text messaging, and a Lessons and Conclusions these events suggest strongly that variety of other technologies, the As in the September earthquake, such policies be reconsidered. In SVA volunteers logged thousands of the liquefaction damage was dram- addition, this earthquake has again person hours delivering chemical atic and widespread. Some resi- reinforced the need for an Earth- toilets, shoveling silt, removing dential areas of Christchurch may quake Buildings Rating System that fallen bricks, sorting donations, and not be rebuilt because ground permits design professionals to

15 EERI Special Earthquake Report — May 2011

communicate the seismic perfor- Safety Evaluation of Buildings, Preliminary Reconnaissance mance of buildings in terms that Redwood City, CA. Report from the Christchurch 22 are easily understood by the public. Beattie, G. J. and S. J. Thurston, Feb 2011 6.3Mw Earthquake. The overall performance of modern 2006. Changes to the Seismic http://db.nzsee.org.nz:8080/en/ buildings in the CBD may satisfy our Design of Houses in New Zea- web/chch_2011/structural/ technical performance standards, land, 2006 NZSEE Conference. King, A. B., et al., 2003. The Austra- but was it acceptable to the public? Bruneau, M. et al., 2011. Steel lia/New Zealand Earthquake Load- Furthermore, after all the damage Building Damage from the New ings Standard, AS/NZS 1170.4. and psychological distress from Zealand Earthquake of February 2003 Pacific Conference on Earth- both quakes, the public trust in all 22, 2011. http://mceer.buffalo.edu/ quake Engineering, Paper #138. buildings within the heavily dam- research/Reconnaissance/New_ Christchurch: New Zealand Soci- aged area was shaken. The Univer- Zealand2-21-11/CHCH_EQ_ ety for Earthquake Engineering, sity of Canterbury went to extreme Steel_damage_2011-03-11.pdf Ministry of Education, 2011, Our lengths to evaluate all its buildings Christchurch City Council, 2011. Responses and Updates, 2011. in order to be able to reassure stu- http://www.minedu.govt.nz/EQNZ dents and staff that buildings were Christchurch Earthquake 22 Feb. safe to occupy. This will be impor- 2011. http://www.ccc.govt.nz/ New Zealand Childcare Association, tant in any large event in the U.S. Civil Defence, 2011. Building Safety 2011. Christchurch Earthquake Emergency Response Sector Finally, the long-term recovery is- Evaluation Team, Christchurch, New Zealand. Briefing — Notes, March 1, 2011. sues for the CBD are critical. With http://www.nzca.co.nz/files/ 25% of the buildings demolished un- Clark, S. J., M. Jones, and I. C. Sector_Briefing_Notes der emergency orders and perhaps Page, 2005. New Zealand 2005 another 25% that could be taken House Condition Survey, BRANZ New Zealand Herald, 2011. “97% down by owners, economic develop- 2005 ISSN: 0113-3675. of Christchurch Schools to open,” ment and a major rebuilding program March 20. http://www.nzherald. Cubrinovski and Taylor, 2011. Lique- will be critical. For the engineering co.nz/nz/news/article.cfm?c_ faction Map — Drive-through Re- professions this raises again the per- id=1&objectid=10713801 connaissance, University of Can- ennial question: what levels of dam- terbury NZ. www.nzsee.org.nz NZS1170.5, 2004. “Structural De- age are acceptable in existing and sign Actions, Part 5: Earthquake new infrastructure, and what per- Environment Canterbury and Actions – New Zealand”, Stan- formance standards can we provide? Christchurch City Council, 2011. dards New Zealand. Canterbury Earthquake. http:// New Zealand Society for Earthquake Acknowledgments canterburyearthquake.org.nz/ Engineering, 2009. Building Safety The team was ably assisted by fac- Environment Canterbury, 2004. The Evaluation During a State of ulty and students from the Univer- Solid Facts on Christchurch Liq- Emergency: Guidelines for Territo- sity of Canterbury, including Bruce uefaction. http://www.ecan.govt. rial Authorities, August. Deam, Rajesh Dhaka, Greg Mac- nz/publications/General/solid- New Zealand Parliament, 2011. Rae, Alessandro Palermo, Stefano facts-christchurch-liquefaction.pdf Pampanin, Erica Seville, and Wang Canterbury earthquake (Edu- GEER, 2011. Geotechnical Kam. Equally valuable was the help cation Act) Order 2011, Order Reconnaissance of the 2011 provided by University of Auckland in Council, March 8. http:// Christchurch (New Zealand) Associate Professor Jason Ingham, www.legislation.govt.nz/regula- Earthquake, GEER Association New Zealand Society for Earth- tion/public/2011/0038/latest/ Report (in preparation). http:// quake Engineering (NZSEE) pres- DLM3586764.html?search=ts_reg- www.geerassociation.org/ ident Peter Wood, consulting engi- ulation_canterbury+earthquake_ neer and head of the Critical Build- GeoNet, 2011, Canterbury Quakes. resel&p=1&sr=1 ings Project David Hopkins, USAR http://www.geonet.org.nz Statistics New Zealand, 2011. http:// engineers Des Bull and Craig Ste- GNS Science, 2011. Canterbury www.stats.govt.nz/browse_for_ venson, Chamber of Commerce Quakes. http://www.gns.cri.nz/ stats/education_and_training/ chief executive Peter Townsend, earthquake-schools.aspx Hare, J., 2011. Christchurch Seismic and City of Christchurch officials, Various news articles between particularly Steve McCarthy. Design Load Levels: Interim Ad- vice, Structural Engineering Soci- February 23 and March 20, 2011, ety of New Zealand, April 2011. http://www.stuff.co.nz/national/ References christchurch-earthquake Applied Technology Council, 1995. Kam, W. Y., U. Akguzel, and S. Procedures for Postearthquake Pampanin, 2011. 4 Weeks On: