EERI Special Earthquake Report — November 2010

Learning from Earthquakes

The Mw 7.1 Darfield (Canterbury), New Zealand Earthquake of September 4, 2010

From September 8th to 20th, 2010, at 4:36 am, as well as to the moder- magnitude at 7.1 with a predomi- a team organized by the Earth- ate level of shaking in the most popu- nantly strike-slip focal mechanism quake Engineering Research Insti- lated areas of the Canterbury region. having a right-lateral focal plane tute (EERI) and the Pacific Earth- New Zealand also benefits from a striking east-west. However, more quake Engineering Research modern structural code and rigorous detailed and ongoing analysis has (PEER) Center investigated the code enforcement. Regional planning revealed a strong reverse faulting effects of the Darfield earthquake. had been undertaken to reduce criti- component to the mainshock. The team was led by Mary Comerio, cal infrastructure and lifelines vulner- The surface rupture spans nearly UC Berkeley, and included Lucy ability to natural hazards about 15 30 km and consists of fault scarps Arendt, University of Wisconsin, years ago (Centre for Advanced Engi- that locally exceed 4 m of right- Green Bay; Michel Bruneau, Uni- neering, 1997), with improvements in lateral and about 1 m of vertical versity of Buffalo, New York; local government and utilities pre- dislocation of the ground surface. Peter Dusicka, Portland State Uni- paredness, as well as the retrofitting In most places along and near the versity; Henri Gavin, Duke Univer- of bridges and other lifeline facilities. fault, the ground surface on the sity; Charles Roeder, University of Christchurch is the largest city on the south side has been raised relative Washington; and Fred Turner, Cali- South Island of New Zealand, and to the north side. Ongoing geodetic fornia Seismic Safety Commission. the country's second-largest urban surveys, including LiDAR and Additionally, individuals sponsored area, with a population of 375,000. InSAR surveys, are measuring by their organizations, or already in While New Zealand has strict seismic these deformations in greater de- New Zealand, joined the team: Tao building codes for new construction, tail. Surface rupture extends west Lai, AIR Worldwide Corporation; Christchurch was not considered a from the town of Rolleston to just Rob Williams and Oliver Boyd, US high-risk area and had a passive ret- southwest of Greendale and then Geological Survey; Myrto Anagnos- rofit policy for its unreinforced mason- trends northwest. In the two-week topoulou, University of Buffalo; and ry buildings. The damage to nonretro- period following the earthquake, William Holmes, Rutherford and fitted URM buildings from the moder- there were over 550 aftershocks Chekene, LFE Program Manager. ate shaking is an important object greater than or equal to magnitude Thomas O’Rourke of Cornell Uni- lesson for other regions with versity visited Christchurch the week large inventories of URM of October 11th. buildings. Unprecedented The research, publication and distri- residential losses due to liq- bution of this report were funded by uefaction and lateral spread- the Earthquake Engineering Re- ing represent a considerable search Institute Learning from portion of the total losses, Earthquakes project, under grant # estimated at $4 billion NZ CMMI-0758529 from the National ($3 billion US). Even for Science Foundation. buildings that performed well structurally, there was exten- Introduction sive nonstructural damage to both building components In the early hours of Saturday and contents. morning on September 4, 2010, people in Christchurch and the sur- rounding Canterbury region were Seismicity jolted awake by the most damaging The earthquake nucleated earthquake in New Zealand since about 10 km below a flat- the deadly M7.8 Hawke's Bay lying agricultural area called (Napier) earthquake in 1931. This the Canterbury Plains, 40 km time there was no loss of life and west of Christchurch, near only two serious injuries. The low the town of Darfield (Figure 1). casualties can be attributed in part GeoNet (http://www.geonet. Figure 1. Location of epicenter and shaking to the time of the M7.1 earthquake org.nz) estimated the moment intensity by city size (source: USGS)

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acceleration at this site ties (Figure 3), causing extensive averaged 0.74 g. The five damage to buried utilities (water sites closest to the surface and wastewater pipelines), resi- rupture (all within about 5 dential housing, and other build- km) had vertical ground ing structures. To a lesser extent, accelerations greater than roads, railroad embankments, and 0.7 g and ratios of vertical levees were also affected. Accord- to horizontal acceleration ing to a 2004 liquefaction suscep- greater than 1.5 — in spite tibility study in Christchurch, ap- of four times more hori- proximately 50% of Christchurch zontal offset than vertical residential areas are vulnerable to along the surface rupture. liquefaction (Environment Can- The ratio of vertical to hori- terbury, 2004). Between 5% and zontal ground acceleration 10% of residential properties in the decreases steadily moving Christchurch area were actually away from the surface affected by liquefaction. Strong motion stations, fault rupture rupture. The station at Figure 2. The Christchurch and Waimakariri (red line) and aftershocks (green circles). Gray Kaiapoi (about 40 km east- Districts, and to a lesser extent the area is the metropolitan area of Christchurch northeast of the epicenter) Selwyn District, all had damage to (source: USGS) is anomalous compared to pipeline networks that resulted in the other stations in that it the loss of service and discharge exhibits very low vertical peak ground 3, including nine greater than M of untreated wastewater into the acceleration (0.09 g) relative to the 5.0. The largest aftershock was an groundwater and surface water. horizontal (~0.33 g). Charles Clifton M 5.6 about 20 minutes after the In all three districts, drinking water (2010) of the University of Auckland main shock. The aftershocks dis- is untreated well water. Most reported that ground accelerations in close a roughly 60 km long east- water mains are asbestos-cement Christchurch were about 70% of the west rupture plane just south of the pipelines, with newer pipelines design values for periods less than epicenter. composed of polyvinyl chloride. 1.5 s, and 100% of the design values Wastewater pipelines in Christ- The earthquake was located on an at longer periods. Farther west, closer church are predominantly rein- unmapped fault that may not have to the rupture, ground accelerations forced concrete conduits. ruptured in the last 16,000 years, exceeded design values at all periods. as evidenced by previously undis- Christchurch City Council (CCC) turbed Pleistocene gravels (GNS Geotechnical Effects and officials estimate that approximately Science, 2010). Prior to this earth- Lifelines 25 km of potable water and 70 km quake, much of the seismic hazard of wastewater pipelines will have in the region was ascribed to the Liquefaction and lateral spreading to be replaced in areas of liquefac- Alpine fault, a major northeast strik- were pervasive in portions of Christ- tion and lateral spreading. Outside ing right-lateral strike-slip fault that church and neighboring communi- separates the Pacific and Australian plates and lies about 100 km northwest of the Darfield earthquake. Very strong ground mo- tions were recorded by strong motion seismom- eters near the rupture. Maximum felt intensities reached VIII (Figure 2). Maximum vertical peak ground acceleration at Greendale (located Figure 3. Structures damaged by lateral spreading about 1 km north of the and post-liquefaction differential settlement. fault scarp) was 1.26 g. (a)  Residential structure in Spencerville; (b)  Horizontal peak ground St. Paul's Church in Dallington (photo: Green).

2 EERI Special Earthquake Report — November 2010 the areas of liquefaction, there pipelines and 10 km of storm lines in River in New Brighton as well as in were approximately 280 locations Kaiapoi were severely disrupted in an area of liquefaction adjacent to of damage in water pipelines that areas of liquefaction and lateral spread- Hagley Park. were repaired within 6 days of the ing. The biggest problems were to the By far one of the greatest impacts earthquake. Liquefied sand and deep gravity wastewater mains, in of this earthquake on the residents water entered sewer lines though many cases 3-4 m below the ground in the Canterbury region was the breaks and separations in the pipe, surface. With ground water only 2 m lateral spreading and post-lique- and cleaning the sand from waste- deep, trenching was difficult. In addi- faction differential settlement that water conduits and pump stations tion, some mains are located in the damaged numerous residential and slowed service restoration. Further- backyards of private residences, other structures (Figure 5). Particu- more, CCC officials expressed con- making access and subsequent larly hard hit were the Christchurch cern about voids that developed be- repairs more difficult. neighborhoods of Dallington, Avon- neath pavements due to the esti- The large vertical movements due side, and Bexley, outlying neighbor- mated 11,000 tons of sand removed to liquefaction caused low points in hood of Halswell (southwest of from pipes and pump stations (cor- some sewer lines, and in the com- Christchurch), outlying neighbor- responding to a potential volume of munity of Kaiapoi sewage is being hoods of Spencerville and Brook- approximately 9,000 m3). pumped from one of these low points lands (northeast of Christchurch), The hardest hit communities in into the river. The effects of these and Kaiapoi and Pines Beach Christchurch were perhaps Spencer- settlements on surface storm drain- (northeast of Christchurch, north of ville and Brooklands. Two weeks af- age have not been determined; the Waimakariri River). ter the earthquake, neither commu- neither have potential nity had functioning wastewater col- effects on river chan- lection systems, and Brooklands was nels and flood plains without potable water. Liquefaction due to changes in grade along Lower Styx road, the primary caused by local fault connection between these two com- movement. munities, caused ground subsid- In contrast to the water ence, raised the water table, and and sewer system, the uplifted 25 manholes. Separation gas distribution system between the manholes and the road performed well. The surface was 28-46 cm (Figure 4). natural gas pipeline The Waimakariri District Council system in Christchurch (WDC) was much harder hit than comprises 170 km of Christchurch, primarily due to the 65-315 mm internal extensive liquefaction and lateral diameter, medium- spreading in Kaiapoi. Approximate- density polyethylene Figure 5. (a)  Large lateral spreading like a rup- ly 30-35 km of water and sewer pipelines with thermal ture passed through the foundation near Courtenay fusion welds. At the time Drive in Kaiapoi. (b)  This house slid more than of the earthquake, the 1.2 m and tilted significantly (near Courtenay Drive gas was a mixture of in Kaiapoi) (photos: Lai). 60% propane and 40% butane at a pressure of approximately 90 kPa. There were no leaks or significant fluctuations of pressure throughout the system during and after the earthquake. Most gas pipelines were located outside zones of liquefaction, although some lines were located in a zone of liquefaction- Figure 4. Uplifted manholes along induced ground defor- Lower Styx road.(photo: Green) mation along the Avon

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mic loading, and there is potential for liquefaction. Indeed, significant liquefaction was observed in many areas around the port. Although the soil movements appeared somewhat less severe than in many other areas near Christchurch, the actual magnitude of vertical and transverse move- ment was not precisely known Figure 6. The port facility at Lyttleton (photo: Roeder). because geometric surveys were not complete by the date of the The Waimakariri River is the source has a full range of shipping, including visit. However, there was clear of greatest flood risk in the Canter- container, dry bulk (coal), finished differential deformation in Cashin bury area. Flood protection includes petroleum products, livestock, and Quay wharves 1 and 2. The land- approximately 100 km of stop other miscellaneous commodities. ward piles had approximately banks, or levees, along the river. The port sustained significant dam- 200 mm downward movement The levees are typically 3-5 m high, age during the earthquake, and port compared to the rest of the wharf, 4 m wide on top, with 3H:1V slopes. engineers estimate total costs at the timber cap beams for the piles Earthquake levee damage was more than $100 million NZ ($75.5 were broken in many locations, and especially pronounced in the lower million US). The harbor is a volcanic there was considerable deformation Waimakariri near Kaiapoi, where caldera with wind-blown silt in the of the precast deck panels on the approximately 5 km of levees upper strata. Seawall areas are con- landward side of the wharf. Both along the Waimakiriri and Kaiapoi structed with hydraulic infill from crane rails rest on the seaward Rivers suffered severe and major harbor dredging. The older wharves side of the wharf, and no relative damage. Severe damage involves have timber piles with precast deck displacement between the rails cracks greater than 1 m in width, panels, which are approaching the occurred so that crane operation with deep-seated movement and end of their useful life, but newer resumed quickly. These move- settlement; major damage entails wharves employ concrete and con- ments caused separation and mis- large-scale instability, with lateral crete-filled steel tube (CFT) piling. alignment of the conveyors (Figure spreading and settlement that The wharf construction is somewhat 7) used for loading coal at these exceeds 0.5 m. different from that used in many ports wharves. These wharves returned in that the piles have shear or pin to service shortly after of the earth- Port connections to the wharf superstruc- quake, but they are not operating at ture, and lateral resistance is primari- full capacity and some parts of the The port serving the Christchuch ly developed through struts or tie- wharves and coal-handling equip- area and South Island is in the backs anchored into the landward ment must be replaced. community of Lyttelton (Figure 6). soil. Geotechnical analyses indicated The facility is relatively small, but it Container ships are loaded at that the stronger and denser re- Cashin Quay wharves 3 and 4, claimed soils over the weaker harbor which are newer structures on con- silt/clay mud are unstable during seis- crete or CFT piles, and had limited damage. The petro- leum products wharf had extensive lique- faction, but limited damage to the load- ing berths, since these were seismical- ly retrofitted in recent years. Coal loading resumed 26 hours after the earthquake, and an LPG ship sailed into port one Figure 7. (a)  (b)  The coal loading machinery at week afterwards. the port (source: Roeder).

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Figure 8. Shear cracks in perim- eter masonry walls of an eight-story reinforced concrete frame building Figure 9. Cracks at beam seats of gravity load precast members used in in downtown Christchurch (photo: parking garage, along with undamaged eccentrically braced frame lateral Dusicka) system in Christchurch area (photos: Dusicka).

Engineered Structures More modern engineered buildings A number of modern buildings had are also reinforced concrete, often broken windows, and a few showed Newer engineered buildings gener- utilizing precast structural compo- signs of structural distress. The ally performed well, but preliminary nents and sometimes mixed (con- WestPac Trust Building is a 14- indications are that the ground crete and steel) construction. One story reinforced concrete frame shaking was below the design re- such example was the Westfield structure in central Christchurch sponse spectra for shorter-period Riccarton Mall, a multi-story shopping with concrete core walls and diago- buildings (periods less than about 2 complex where precast panels were nally reinforced coupling beams seconds). The majority of larger and combined with steel eccentrically (Figure 11). The perimeter beams multi-story buildings in the affected braced frames (EBFs) on a multi- were precast concrete elements area are located in downtown story garage. Relative movement of that form an apparent truss. A Christchurch and on the University the precast panels of approximately secondary shallow concrete beam of Canterbury campus. Reinforced 0.25 in was apparent from the steel appears to be located behind the concrete construction is prevalent, connector brackets and cracking truss, but does not connect to the with older buildings being typically damage to a couple of the precast centerline of the column. The col- reinforced concrete moment beam seats; however, the steel lateral umns are spalled at the beam- frames. A number of these older system did not appear to be affected column connection for all connec- buildings also had masonry infill (Figure 9). walls, but we observed very limited structural damage to these struc- One reinforced concrete building con- tures. This is likely attributable to structed about 1960 was situated the lower-than-design-level de- alongside the Avon River in an area mands that are suspected to have with significant liquefaction and lateral been imposed on the shorter-period spreading. This building sustained structures. One of the most visible significant damage (Figure 10) be- exceptions was an eight-story build- cause of lateral spreading under ing consisting of reinforced con- the foundations of the columns. The crete frames with a double cavity column line adjacent to the river wall of unreinforced masonry bricks shows soil movement. Most damage around the building. Severe shear is concentrated in the beam-column Figure 10. Damage to a reinforced cracks were visible in the masonry connections since many bays of the concrete building from lateral on both the exterior and interior of building have masonry infill that pro- spreading at a site near the Avon the building (Figure 8). vides a very stiff structure. River (photo: Roeder)

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Figure 12. (a)  Yielding in the link beam of an ec- centrically braced frame (b)  and a severely dam- aged concrete column in a parking garage in down- Figure 11. Perimeter column town Christchurch (photos: Roeder). spalling throughout the height of a reinforced concrete frame with perimeter precast trusses in West- non-uniform yielding in the steel Six pedestrian bridges, not en- Pac building in downtown Christ- frames. In addition, several concrete dowed with similar strengths and church (photo: Dusicka) columns located on the upper ramp stiffness to resist the demands ap- were severely damaged (Figure 12b). plied to them as a consequence of tions at lower levels, and for many the liquefied soils, did not fare as levels of the structure. The spalling Bridges well and will need replacement. One was increasingly more severe and notable example is the pedestrian Overall, bridges in the Canterbury clearly distributed throughout the steel truss bridge over the Avon area suffered little damage. This was height when observed two days River in Christchurch that buckled due a complex set of circumstances: after the initial survey. The spalling axially under thrust imposed by the 1) most have small to moderate was mitigated by manual removal of movements of its abutments due to spans, which are recognized to ex- loose concrete and clearly exposed the lateral spreading action of soils hibit a more sturdy seismic response the main and transverse reinforcing on top of liquefied layers (Figure 13). because of their symmetry and limit- at some locations. This introduced compressive forces ed reactive mass; 2) most were de- in the bridge truss chord, forces Steel structures are not common in signed to resist forces substantially unanticipated in the original design Christchurch, and the relatively few larger than the demands imparted by that led to local buckling of some performed quite well. However, this particular earthquake; and 3) they chord members, twisting of the steel eccentrically braced frames shared a number of common design superstructure, and uplifting at a (EBFs) were used with concrete col- features that gave them high seismic support location above one of the umns in several buildings, in some resistance, including a sturdy mono- braced pier in the river. cases as a retrofit. One relatively lithic structure in both their longitudi- new parking garage employed this nal and transverse directions, wide Schools concept to provide lateral resis- wall piers that provided stiffness and tance to other framing made of strength in excess of the values Most schools in the Christchurch precast concrete, likely to enable needed to resist severe excitations (171 schools, 59,736 students), rapid construction. Numerous EBFs transversely to the axis of the span, Selwyn (30 schools, 7,818 stu- indicated yielding in the link beam, and continuity of the superstructure dents), and Waimakariri (25 schools, illustrating the engagement of the from abutment to abutment that pro- 6,618 students) districts opened lateral system and protecting most vided a rigid behavior in the longitu- one week after the earthquake. The of the precast beam and column dinal direction. While the wall piers of oldest schools have heritage build- gravity structure (Figure 12a). The these bridges were likely supported ings — typically multi-story unrein- garage had long inclined concrete on piles, damage to such piles would forced masonry structures almost ramps along one edge of the build- be difficult to identify even if it were a century old. Newer school cam- ing, which possibly caused torsional present. puses typically contain timber-frame deformation that might explain the single-story structures with unrein-

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hospital, an older- E-W direction. The estimated 70-90 persons care mm peak isolator drifts are well be- hospital, and an low the 420 mm design displace- outpatient hos- ment, for a 2,000-year return period pital. There are demand. The estimated peak dis- also two large placements are probably not incon- private hospitals sistent with the observation that in Christchurch. spectral demands in Christchurch for this event were close to the Immediately fol- 10%/50yr level for long-period struc- lowing the earth- tures (Figure 14). quake, all area hospitals re- The base-isolated Christchurch mained opera- Women's Hospital building connects tional, including to the adjacent Christchurch Hospi- the Christchurch tal through seismic joints, with sac- Figure 13. Pedestrian bridge, River Road–Avonside Hospital Emer- rificial wall panels, ceilings, and floor Drive, Christchurch (photo: Bruneau). gency Depart- mats. Damage to these sacrificial ment. Backup components increased up the height forced slab-on-grade foundations. generators for of the structure, with evidence of Nine schools remained closed be- Christchurch and Burwood Hospitals larger motion in the NS direction. An yond one week for further structural were operational within 15 seconds of unsecured bookshelf on level 5, the evaluations and repairs. losing power, and full power to these only unsecured shelf on that floor, facilities was restored within 80 min- toppled. Most of the water in a half- While very few schools sustained utes. The two urgent care facilities full birthing pool on level 3 sloshed significant losses to contents, 75% in the affected area (Riccarton Clinic out, and carts rolled across the of them required minor repairs (re- and Moorehouse Medical and Phar- floors. The aftershock sequence has arranging toppled contents, repair- macy) opened by 8:00 a.m. the morn- led to motion-sickness complaints ing broken windows, replacing ceil- ing of the earthquake. from staff working in levels 4 and 5 ing tiles). Most schools reopened of the base-isolated facility. after 50 person-hours or less of Staff at three small community hos- pitals (Lincoln Maternity Hospital, work in each one, but about 20% of Housing and Insurance them required 200 person-hours or Burwood Birthing Unit, and Akaroa more to make necessary repairs. Hospital) were relocated to the main Almost all housing in the Christ- Christchurch Hospital campus in order church region is single-family wood- Halswell Primary and St. Paul's to ensure that it had adequate staff to frame, most of it one story. Many of School suffered significant liquefac- run in 24/7 shifts. These three facilities the older homes had unreinforced tion-induced damage to foundation were closed from September 5th to masonry chimneys, highly vulner- slabs and piled foundations; Hals- 15th, although there was no signifi- able to earthquake damage, and to well School is sited near a former cant damage to any of them. date there have been more than river bed and St. Paul's School is 14,000 claims for damaged chim- within a bend of the Avon River. The Christchurch Women's Hospital At Halswell, eight classrooms, the opened in 2005 and staff room, and the administration is the only base-iso- area are slated for demolition and lated structure in the reconstruction in the summer. Stu- South Island. The dents are being split among three superstructure con- other school campuses for the sists of an exterior remainder of the year. precast frame with steel Vee bracing up Hospitals to Level 4 (out of 9), and was detailed to a The Canterbury District Health ductility capacity of Board manages 15 hospitals, in- 1.8. Following the cluding three major ones in Christ- earthquake, a 25 mm church, a rural hospital, six small residual displacement community hospitals, two small in the isolator system Figure 14. Aspect of the base-isolated hospital build- maternity hospitals, a psychiatric was observed in the ing (source: Gavin).

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neys. The homes are predominantly national reinsurers. The government ment approval process is likely to concrete slab on grade with a light guarantee ensures that EQC will al- be an issue for insurance and re- perimeter grade beam, as opposed ways be able to meet its obligations, construction. Furthermore, the dam- to the US approach of using wood- regardless of the circumstances, and age will represent a devastating framed first floors over crawl spaces. the reinsurance program provides loss to homeowners unless they Although crawl spaces create their protection for the fund in case of a have private insurance in addition own earthquake vulnerability, such large natural disaster. to the EQC coverage. Even then, a system is probably better under the additional cost of demolition and After a major disaster, the EQC works severe liquefaction conditions, be- foundation strengthening will leave through its Catastrophe Response cause the wood floor is more toler- the homeowners in a dilemma con- Program (CRP) with local engineering ant of slight differential settlements cerning the suitability of the site for consultants to augment their capacity and the crawl space can be used to rebuilding. City regulators, insurers, to cope with the substantial in- raise and/or relevel the superstruc- and the EQC must decide if the crease in demand for services and ture. sites can be reused and, if so, resources. EQC also actively partici- under what required structural or In 1945, the government estab- pates and funds earthquake-related soils modifications. lished an insurance program to pro- research. Because liquefaction dam- tect its residents from the financial age after this earthquake was wide- At the time of this report, EQC re- impacts of war. Later, this was re- spread and quite severe, EQC devel- ported a total of 87,928 claims from purposed as coverage for natural oped a process to standardize the the earthquake. Since new claims catastrophes such as earthquake, assessment of liquefaction damage. are being submitted daily and landslide, tsunami, volcanic erup- EQC proposed the classifications claims settlements are in process, tion, hydrothermal activity, and flood below, and formulated a calculation it is still too early to determine the (land only). It is administered by the of land damage given the liquefaction exact monetary loss for residential Earthquake Commission (EQC), damage state and a normalized resi- dwellings. However, given the pat- which provides fire insurance as dential land area that varies by rural tern of claims submission, it is very well, and is required with every and urban dwellings: likely the total number of claims mortgage. Commercial owners are • Significant liquefaction land dam- will reach 100,000, as the EQC not under the EQC umbrella, and age: major lateral spreading had originally expected. Given the have to purchase protection solely • Major liquefaction land damage: current damage statistics — more from private insurers. major settlements and minor lateral than 14,000 chimneys damaged, spread approximately 3,000 dwellings likely The EQC insurance policy costs • Moderate liquefaction land damage: to be demolished, and average homeowners $67.50 NZ per year, moderate settlements dwelling damage cost of $300,000 and provides protection of up to • Minor land damage: no surface ev- NZ — the total residential loss will $100,000 NZ for a dwelling (build- idence of liquefaction likely be around $3 billion NZ. EQC ing), and $20,000 NZ for contents • Structural shaking damage only: no will be responsible for more than (personal belongings). In addition, if obvious land damage half that figure. the site is destroyed (originally con- ceptualized for landslides, but appli- As an example of the complications Post-earthquake assistance is also cable in the liquefaction zones), an involved, Figure 5 shows two dwell- available to local governments amount for the land lost can also be ings in Kaiapoi that were severely through the Local Authority Pro- added. When the actual damage damaged due to large lateral spread- tection Programme (LAPP) (Civic is beyond the EQC limit, either ing. In the first photo, the lateral Assurance, 2010), which is a trust private insurers or homeowners will spreading created a large ground fund established in 1993 to help be responsible for the difference, rupture passing through the founda- New Zealand local authorities pay depending on the additional insur- tion and leaving this house uninhabit- the infrastructure replacement ance purchased by homeowners. able. In the second case, the entire costs for water, sewerage, and Approximately 85% of New Zealand house moved, mostly with the sur- other essential services damaged homeowners have EQC-backed rounding soil about 1.2 meters to the by natural disasters. Of 85 local earthquake insurance coverage rear, which overlooks a wetland. It is authorities, 59 are currently fund through private insurers. Over the expected that both dwellings will have members. For example, the CCC past 60+ years, EQC has been col- to be demolished; however, it will be and Waimakariri District Council are lecting premiums from the insureds difficult to determine financial respon- members, but the Selwyn District and has generated around $5.6 sibility since the large lateral spread- Council is not. Under the fund, 60% billion NZ for the Natural Disaster ing could be associated with the de- of replacement cost is to be cov- Fund, which is further backed up by velopment’s location adjacent to pub- ered by the national government, a government guarantee and inter- lic wetlands. The role of the develop- with the remainder covered by

8 EERI Special Earthquake Report — November 2010 member contributions. The cost of Throughout the city, loose masonry are particularly relevant to U.S. and the earthquake repairs exceeds the fell from unbraced parapets and gable Canadian practice, since New Zea- size of the insurance pool (approxi- walls (Figures 15 and 16). In a large land’s methods are quite similar to mately $40 million NZ), and the role number of cases, entire parapets and those in North America. of the national government in at- upper walls not adequately attached In older commercial districts, many tending to the additional costs is yet to roofs fell onto streets, sidewalks, modern and generally lightly dam- to be determined. and adjacent smaller buildings. aged buildings and their occupants Only some of the URM buildings ap- were indirectly affected by severely Unreinforced Masonry peared to be partially or fully retrofit- damaged URM buildings nearby. Building Performance ted prior to the earthquake. Parapet Several blocks throughout were New Zealand’s building stock re- bracing was apparent in some, often closed for cleanup and stabilization sembles that of the western part of only on walls over busy streets. Be- of buildings with loose masonry North America. With the shaking cause Christchurch was considered falling hazards, handicapping traffic intensity in Christchurch varying to be in a region of moderate seismic and commerce. The masonry falling between VII and VIII, the Central hazard, the regional government had on sidewalks, on outdoor restau- Business District had severe dam- encouraged voluntary retrofits of rants, and on neighboring smaller age in some unreinforced masonry collapse-prone buildings. Although buildings would have caused many (URM) brick commercial and stone statistics are not available at this casualties if the earthquake had institutional buildings. The Canter- time, anecdotal evidence indicates struck during the day or early eve- bury Region has 958 URM build- that retrofitted or partially retrofitted ning hours. The extremely high risk ings; of the 595 URM buildings URMS performed well compared to in and around these few buildings assessed after the earthquake in similar unretrofitted buildings nearby. again confirms the high life safety risk of URM buildings very similar to Christchurch (apparently concen- Various techniques were used for ret- those found in many parts of the U.S. trating on the CBD), 21% received rofitting URMs: through-bolts, adhe- red "unsafe" placards, and 28% sive anchors, fiber reinforced poly- In response to the earthquake, received yellow "restricted use" mers, grout injections, added steel Christchurch's City Council followed placards. Over 160 buildings suf- moment frames and braced frames, prior recommendations from New fered more than 10% damage and concrete moment frames and walls, Zealand's national government and many of these have since been new roof diaphragms, and external enacted a policy requiring 7,600 demolished (Ingham and Griffith, steel rods, angles and plates. These "earthquake-prone" buildings (those 2010). retrofit methods appeared to preclude with less than 33% of the lateral Stair-step and X-cracking in the collapse and did not exhibit system- strength required for new buildings) plane of walls was observed in two atic vulnerabilities to the particular to be evaluated and retrofitted within seven-story URM buildings in the ground motions of the earthquake. 15-30 years, depending upon their district, but was only rarely noted in However, there was minor damage in occupancy, to ensure that they the low-rise URM buildings. Many several retrofitted buildings, as would have at least 67% of the strength of the severely damaged buildings be expected. Efforts to document the required for new buildings. All con- had relatively low mortar strength. performance of retrofitted buildings struction types except low-rise

Figure 15. This corner building had braced parapets only fronting on the main street, left. The secondary street wall Figure 16. Blackwell’s Department Store on William separated from the roof, falling onto the street and side- Street in Kaiapoi suffered extensive structural damage walk below (photo: Turner). (photo: Arendt)

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built in the 1950s-1970s on the west side of Christchurch. The building stock is predominantly 3-12 story concrete construction. University staff had done excellent earthquake preparedness planning and imme- diately organized safety inspections and detailed building assessments. About one third of campus buildings had some nonstructural damage, while 75% had contents damaged (files overturned, books off shelves, shelves overturned, fallen lab equipment, broken beakers). The nonstructural damage was primarily to stairs, finishes at seismic joints, ceilings and elevators (Figure 17). Some sprinklers were set off by Figure 17. Nonstructural damage ceiling movement, and one eight- at the University of Canterbury: story building had an open water fallen ceiling tiles and hangers Figure 18. At the University of Can- tank on the roof. The water sloshed (photo: Comerio) terbury, laboratory experiments had to be rebuilt. (photo: Comerio) out of the tank and caused water damage in labs. dwellings are included in the 7,600 The university was initially closed buildings affected by this new policy. transportation corridor of Highway 1 for one week, but during the clean- Efforts are also underway to estab- along the South Island east coast. up, it was decided to extend the lish funds for repairing high-priority Six days after the earthquake, a large closure for a second week, with a heritage buildings to minimize the landslide (approximately 90,000 m3) phased return of staff and students loss of integrity to historical districts closed the transportation corridor in the second week. Staff and grad- (Christchurch City Council, 2010). (both highway and railroad) near uate student researchers were al- There was only one fire in a URM Kiakoura, about 175 km north of lowed in to clean up their offices building in the Central Business Christchurch, for four days. Food and make repairs (Figure 18), and District caused by restored electric- shipments were then diverted onto faculty met to organize the teaching ity igniting liquid propane gas. Highway 73 in mountainous terrain, and exam schedule for the end of which was threatened by severe the semester. Nonstructural Losses, weather. At Lincoln University, an agricultural Multihazards and Impacts Damage to industrial storage racks research university with 4,000 stu- on Universities was observed at many locations after dents in SW Canterbury, the dam- the earthquake. Such damage, es- Much of the nonstructural damage age to pre-76 code buildings was pecially with respect to the food sup- similar to that at UC, with 181 at universities and in office, com- ply, illustrates the importance of non- mercial, and warehouse buildings broken windows in one building. structural mitigation for secondary Library books were knocked off was removed before the EERI team building systems and contents. The arrived, but discussions with engi- shelves and lab beakers were bro- disruption of transportation routes to ken, but there was not significant neers and news reports suggest Christchurch illustrates the effects of that there was significant nonstruc- contents damage. A complex of multiple natural hazards on critical historic URM buildings suffered tural damage to both building com- lifelines. To dispose of the food lost ponents and contents. significant cladding and gable dam- by storage rack collapse, a new cell age (Figure 19), but the exterior bay Storage racks for food supplies at was opened in the city landfill to ex- and wall of an adjacent building two regional distribution centers pedite removal and thereby avert a were undamaged, since it had been collapsed during the earthquake, health hazard. retrofit with a new interior structure. losing a month’s food supply for The University of Canterbury is the The institution was closed one Christchurch. To compensate for 2nd oldest in New Zealand. The ori- week, after which students were the lost storage, food shipments by ginal campus is now the downtown back in class and in their labs. truck and train were undertaken “Art’s Centre,” and the current cam- Many students (particularly inter- from the North Island down the pus (with about 13,500 students) was national students) stayed in dorms

10 EERI Special Earthquake Report — November 2010

quake, but areas of the CBD remained cordoned off even two weeks after the event (Figure 20). Conversations with citizens suggested strong support for Figure 19. Ivey Hall (a)  at the Lincoln Uni- the government’s versity campus was partially retrofitted prior response and a to the earthquake and performed remarkably strongly held belief well, whereas (b)  the adjacent unretrofitted that overall recov- Memorial Hall had severe damage at its gable Radio and web-based an- ery would be quickly achieved. walls (photos: Turner). nouncements urged citi- People were generally stoic about zens to stay home and to the earthquake and its aftermath, on campus during the week the check on their neighbors. Concerns stating that they needed to get on university was closed and helped about water and sewage prompted with their lives and planned to do with the clean-up. Christchurch’s mayor to tell citizens to so. Some manifestations of stress conserve water, not flush toilets, and were evident, but they were infre- Response and Recovery avoid going out to see damage. With- quently expressed. The New Zea- out power, wireless phone systems in land government created a website Injuries: There were no fatalities homes connected to landlines were containing a wealth of information directly attributable to the earth- unusable. People were encouraged for citizens (http://www.canterbur- quake. Two people were reported to use wired landlines or cell phones, yearthquake.govt.nz/) about the seriously injured, one by a collaps- but to limit their use to emergency earthquake and planned recovery. ing chimney and another by flying calls. Power was restored within 18 National legislation was passed glass. hours to 90% of the Christchurch within two weeks of the quake to Disaster response: Local and na- area. In Kaiapoi, just outside Christ- expedite recovery. church, water and sewage were still tional government response to the Business and insurance: Busi- not restored to all locations ten days early morning earthquake was swift. nesses in Christchurch fared well after the quake. The National Crisis Management overall. There was minimal observ- Centre in Wellington was activated A curfew was established for parts of able structural damage, other than immediately after the quake, and Christchurch’s Central Business Dis- in URM buildings. Smaller busi- Civil Defense declared a state of trict (CBD), mainly due to damage to nesses that had nonstructural or emergency for Christchurch, the many unreinforced masonry buildings contents damage generally reported Selwyn District, and the Waimakariri and debris in the streets. Large sec- that they had addressed problems District less than six hours after the tions of the CBD’s streets were cor- themselves or with contractor help. quake. Both the mayor of Christ- doned off to protect potential shop- Most Christchurch businesses re- church and the country’s Prime Min- pers and those wanting to see the opened within a few days of the ister were quick to reassure citizens damage. Street clean-up in the CBD quake, many reporting that they had of the government’s support. began early in the afternoon after the “no business interruption, but also

Figure 21. This Asian Supermar- ket on Riccarton Rd, Christchurch, reopened two weeks after the quake despite damage suf- fered when the adja- Figure 20. The building housing Angus Don- cent URM collapsed aldson, and other businesses on Colombo St. (photo: Arendt). in Sydenham, is cordoned off two weeks after the quake (photo: Arendt).

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no business” because people each of these areas will require con- William Godwin, Fugro William stayed home in response to the gov- siderable expense to repair. For Lettis & Associates, Inc.; Tam ernment’s request that they do so. homes, the universal insurance pro- Larkin, University of Auckland; and vided by the EQC will fund a portion Elizabeth Bowman, University of Businesses in URMs or those adja- of the repairs, but URM losses and Canterbury. cent were the hardest hit (Figure 21). nonstructural repair and clean up Within 14 days of the quake, many costs will exceed coverage when the of the smaller damaged URMs had References costs are fully estimated. The dam- been demolished, leaving their pre- Centre for Advanced Engineering age leaves the city of Christchurch vious tenants without a venue. (CAE), 1997. “Risk and Realities, and the region with a number of ma- Signs were posted in front of many A Multi-disciplinary Approach to the jor planning and engineering questions demolished buildings or those Vulnerability of Lifelines to Natural regarding residential neighborhoods closed to occupancy to inform cus- Hazards.” Report of Christchurch on soft soils and rebuilding the down- tomers about new locations. Engineering Lifelines Group, CAE, town. In addition to structural and University of Canterbury. Christ- In Kaiapoi, a community that suf- geotechnical lessons, the earthquake church, New Zealand. fered significant liquefaction and will provide instruction in the long- Christchurch City Council, 2010. lateral spreading, about 40% of the term efficacy of the recovery and "Earthquake-Prone Dangerous and businesses reopened within a week policy decisions made in the next few Insanitary Buildings Policy 2010." of the quake, and 70% reopened months. 9/10/10. http://www.ccc.govt.nz/ within two weeks. Access through thecouncil/policiesreportsstrategies/ the main shopping area in Kaiapoi Acknowledgments policies/groups/buildingplanning/ was disrupted by retail buildings earthquakepronebuildingspolicy. The team was assisted by faculty and that had been heavily damaged, aspx students from the University of Can- including Blackwell’s, a department Civic Assurance, 2010. “Local Authority terbury. Faculty included Henri Gavin store that had been a mainstay for Protection Programme,”,10/17/10. (on sabbatical there from Duke), Andy more than 135 years (see Figure http://www.civicassurance.co.nz/ Buchanan, Bruce Deam, Rajesh 16). Due to soil movements, Kai- ProductsAndServices/LAPP.htm Dhaka, Greg MacRae, Alessandro apoi had major issues with its water Palermo, Steffano Pampanin and Clifton, Charles, 9/11/2010. New Zea- supply and sewage system, both of land Society for Earthquake Engi- Erica Seville. which conspired to hamper busi- neering: http://db.nzsee.org.nz: ness reopening. New Zealand Society for Earthquake 8080/web/lfe-darfield-2010/ Engineering (NZSEE) President Peter structural/-/blogs/comparison-of- Some small businesses reported Wood provided gracious assistance earthquake-intensity-versus-nzs- that they had some business inter- to the team. 1170-5-design-1 ruption insurance (e.g., $2,500 NZ Environment Canterbury, 2004. per week) in addition to insurance A separate team from the Geo-engi- The Solid Facts on Christchurch for their structure and contents, but neering Extreme Events Reconnais- Liquefaction. http://ecan.govt.nz/ it was not possible to ascertain pre- sance Association (GEER) also publications/General/solid-facts- cisely how many did and whether contributed to this report. The GEER christchurch-liquefaction.pdf they were adequately covered. A team was led by Russell Green of GeoNet (http://www.geonet.org.nz) large number were still in the pro- Virginia Tech, and included Misko cess of determining claim amounts. Cubrinovski, University of Canterbury GNS Science, 6/9/2010: http://www. (NZ-Lead); Tara Hutchinson, UC San gns.cri.nz/Home/News-and-Events/ Issues for Future Scrutiny Diego; Rolando Orense, University Media-Releases/16000-years of Auckland; Ed Kavazanjian, Ari- Ingham, Jason and Mike Griffith, 2010. The earthquake was notable for zona State University; Scott Ashford, "Performance of Unreinforced three main reasons: 1) serious liq- Oregon State University; Brady Cox, Masonry Buildings during the 2010 uefaction and lateral spreading University of Arkansas; Kelly Robin- Darfield (Christchurch, NZ) Earth- damage to homes (as well as son, University of Canterbury; John quake.” Draft 9/27/10. NZSEE schools and other low buildings) Clearinghouse: http://db.nzsee. Allen, TRI/Environmental, Inc.; M. located on soft soils and sand; org.nz:8080/web/lfe-darfield-2010/ Jawad Arefi, University of Canter- 2) considerable damage to non- home bury; Merrick Taylor, University of retrofitted URM buildings, many of Canterbury; Mick Pender, University Local New Zealand News and Govern- which are historic structures; and of Auckland; Liam Wotherspoon, ment Sources: http://tvnz.co.nz/ 3) widespread nonstructural dam- national-news/latest-updates- University of Auckland; Thomas Algie, age to both building components canterbury-earthquake-3759958, University of Auckland; Brendon and contents, even in buildings with http://www.canterburyearthquake. Bradley, University of Canterbury; little structural damage. Effects in govt.nz/

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