(A)(B)(C)▲▲Figure 15. Bridges with damage not associated with liquefaction: A) Moorhouse Avenue, B) Port Hills, C) Horotane.east direction (Figure 2). Shown in Figure 15C, the bridge is adual three-span reinforced concrete bridge supported by singlepier bents. The end spans are supported by seat-type abutments,with the structure spanning between two large builtupembankments approximately 9 m high. The embankmentslopes beneath the abutments and parallel to the roadway havean angle of about 33° relative to the horizontal (i.e., 1.5H:1Vslope). This bridge is ~200 m from the Port Hills Overbridge,and had also been recently retrofitted using a similar approach,with abutment seat extensions and linkages between the bridgeelements.This bridge did not suffer any damage during the Darfieldearthquake. During the Christchurch earthquake, the retrofitmethod appeared to have worked well in terms of protectingthe structure. The ties between spans and at the abutmentselongated and pulled out, as they had in the Port HillsOverbridge. Additionally, 60% of the bolts that attached thesoffit of the precast concrete beams to the abutment seat extensionhad sheared off.The northwest abutment back-rotated 1° and a transversecrack developed at the top of the northwest slope near theconcrete abutment; however, this was not continuous acrossthe slope. The southeast abutment back-rotated by 3.4°and atransverse crack developed at the bottom of the slope on thenortheast side. A significant transverse crack 10 cm wide and60 cm deep opened up at the top of the southeast slope and wascontinuous across the width of the bridge. A transverse scarpalso developed near the toe of the 13-m-long slope, extendingbetween the southern piers of the two bridges, suggesting thata slope failure had been initiated in the embankment fill butdid not become unstable. Movement was also evident perpendicularto the bridge axis, with cracking in the slope extendingthrough the abutment, resulting in wide cracking and lateralmovement of the abutment and superstructure (Figure 17).CONCLUSIONS▲▲Figure 16. Moorhouse Avenue Overbridge pier flexural bucklingfailure.Overall, the bridges in Christchurch and the Canterburyregion performed well during the Darfield and Christchurchearthquakes, given the magnitude of the observed groundmotions. Of those bridges that were damaged, the majoritywere as a result of liquefaction-induced lateral spreading, withonly four bridges suffering damage not related to liquefactioneffects. Even though the larger-magnitude Darfield eventaffected a much wider region, the location of the Christchurchevent resulted in more significant damage due to the intensityof shaking in a region of the city with many bridges and highliquefaction susceptibility.As a result of the significant lateral spreading, the mostaffected components of the bridges were the approaches, abutments,piers, and foundation system. Bridges were able to resistthe inertial forces due to shaking, while the compressive lateralspreading forces resulted in abutment rotation and foundationdamage. For almost all cases the predicted and observed lique-962 Seismological Research Letters Volume 82, Number 6 November/December 2011
Events Reconnaissance (GEER) Association activity througha CMMI-00323914 and NSF RAPID grant CMMI-1137977.However, any opinions, findings, and conclusions or recommendationsexpressed in this material are those of the authorsand do not necessarily reflect the views of the National ScienceFoundation. We acknowledge the New Zealand GeoNet projectand its sponsors EQC, GNS Science, and Land InformationNew Zealand for providing ground motion records used in thisstudy.REFERENCES▲ ▲ Figure 17. Abutment damage and superstructure movementof the southeastern abutment of the Horotane Overbridge.faction occurrences were in close accord, independent of whetherthe liquefaction was evaluated using the V s , DCPT, or CPT.Settlement of bridge approaches affected the serviceabilityof many of the affected bridges, and bridges critical to the networkwere seriously damaged, causing significant traffic disruptionimmediately following the event. Nevertheless, the overallnetwork performed well, with only the Moorhouse AvenueOverbridge closed for an extended period of time. This goodperformance is attributed to the fact that most ChristchurchCity Council road bridges built in the 1950s and 1960s wererobust integral bridges. For the recently constructed bridges,good performance was a result of the significant improvementin bridge seismic safety in New Zealand and retrofittingefforts in the past decade. Additionally, the regular configuration,limited span length, and effective restraining methodswere important factors in the reduced vulnerability of theChristchurch bridge network.ACKNOWLEDGMENTSDr. Wotherspoon’s position at the University of Aucklandis funded by the New Zealand Earthquake Commission(EQC). The primary support for the U.S. GEER team memberswas provided by grants from the U.S. National ScienceFoundation (NSF) as part of the Geotechnical ExtremeAllen, J., S. Ashford, E. Bowman, B. Bradley, B. Cox, M. Cubrinovski,R. Green, T. Hutchinson, E. Kavazanjian, R. Orense, M. Pender,M. Quigley, and L. Wotherspoon (2010). Geotechnical reconnaissanceof the 2010 Darfield (Canterbury) earthquake. Bulletin of theNew Zealand Society for Earthquake Engineering 43 (4), 243–320.Andrus, R. D., and K. H. Stokoe II (2000). Liquefaction resistance ofsoils from shear-wave velocity. ASCE Journal of Geotechnical andGeoenvironmental Engineering 126 (11), 1,015–1,025.Beavan, J., E. Fielding, M. Motagh, S. Samsonov, and N. Donnelly(2011). Fault location and slip distribution of the 22 February 2011M W 6.2 Christchurch, New Zealand, earthquake from geodeticdata. Seismological Research Letters 82, 789–799.Bowen, H. J., and M. Cubrinovski (2008a). Psuedo-static analysis ofpiles in liquefiable soils: Parametric evaluation of liquefied layerproperties. Bulletin of the New Zealand Society for EarthquakeEngineering 41 (4), 234–246.Bowen, H. J., and M. Cubrinovski (2008b). Effective stress analysis ofpiles in liquefiable soil: A case study of a bridge foundation. Bulletinof the New Zealand Society for Earthquake Engineering 41 (4), 247–262.Bradley, B. A. (2010). NZ-Specific Pseudo-spectral Acceleration GroundMotion Prediction Equations based on Foreign Models. University ofCanterbury, Department of Civil Engineering, 319 pp.Bradley, B. A., and M. Cubrinovski (2011). Near-source strong groundmotions observed in the 22 February 2011 Christchurch earthquake.Seismological Research Letters 82, 853–865.Bradley, B. A., M. Cubrinovski, R. P. Dhakal, and G. A. MacRae(2010). Probabilistic seismic performance and loss assessment ofa bridge-foundation-soil system. Soil Dynamics and EarthquakeEngineering 30 (5), 395–411.Brown, L. J., R. D. Beetham, B. R. Paterson, and J. H. Weeber (1995).Geology of Christchurch, New Zealand. Environmental &Engineering Geoscience 1 (4), 427–488.Brown, L. J., and J. H. Weeber (1992). Geology of the Christchurch UrbanArea. Institute of Geological and Nuclear Sciences. Lower Hutt,New Zealand: GNS Science.Gledhill, K., J. Ristau, M. Reyners, B. Fry, and C. Holden (2011).The Darfield (Canterbury, New Zealand) M w 7.1 earthquake ofSeptember 2010: A preliminary seismological report. SeismologicalResearch Letters 82 (3), 378–386.Goda, K., and H. P. Hong (2008). Estimation of seismic loss for spatiallydistributed buildings. Earthquake Spectra 24, 889–910.Green, R. A., C. Wood, B. Cox, M. Cubrinovski, L. Wotherspoon,B. Bradley, T. Algie, J. Allen, A. Bradshaw, and G. Rix (2011).Use of DCP and SASW tests to evaluate liquefaction potential:Predictions vs. observations during the recent New Zealand earthquakes.Seismological Research Letters 82, 927–938.Guidotti, R., M. Stupazzini, C. Smerzini, R. Paolucci, and P. Rameri(2011). Numerical study on the role of basin geometry and kinematicseismic source in 3D ground motion simulation of the 22February 2011 M W 6.2 Christchurch earthquake. SeismologicalResearch Letters 82, 767–782.Seismological Research Letters Volume 82, Number 6 November/December 2011 963
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Volume 82, Number 6 November/Decemb
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News and Notes (continued)Nominatio
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Preface to the Focused Issue on the
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TABLE 1Peak ground acceleration (PG
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▲▲Figure 2. A) Sketch of the
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▲▲Figure 4. A) Adopted moment r
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▲▲Figure 7. As in Figure 6 but
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▲ ▲ Figure 8. Misfit parameters
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▲ ▲ Figure 10. Spatial variabil
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▲ ▲ Figure 12. Standard spectra
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Quigley, M., R. Van Dissen, P. Vill
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slip on a 59-degree striking fault
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▲▲Figure 4. Convergence of inve
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observations and other source studi
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“Product CSK © ASI, (ItalianSpac
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TABLE 2Solutions for fault location
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-43.45(A)degrees N-43.50-43.552.52.
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is still a good fit to the horizont
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Coulomb Stress Change Sensitivity d
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mation takes on a larger strike-sli
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P 9.4267BLDU45P 20.1213CASY39P 2.62
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ERMJNUMAJOINUJHJ2CBIJMIDWJOWYHNBTPU
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(A)6.146.13(B)6.246.36Misfit6.156.1
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(A)(B)(C)(D)▲▲Figure 10. The co
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(A)(B)(C)(D)▲▲Figure 12. The co
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Luo, Y., Y. Tan, S. Wei, D. Helmber
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−44˚00' −43˚00'4-Sep-2010Mw 7
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TABLE 1Pairs of SAR imagery used in
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Depth (km)Coulomb Stress Change(bar
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Crippen, R. E. (1992). Measurement
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AlpineFaultHope Fault38 mm/yr0+ +-1
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σ 1dσ 3Nuσ 3CM w 7.1dw 6.2u70°M
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Right-lateral Faults(A) Range Front
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DISCUSSIONThe 2010-2011 Canterbury
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Large Apparent Stresses from the Ca
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▲ ▲ Figure 2. Observed vs. pred
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10Obs SA(1s)AS1AS+SDAB 2006AB+SDSA(
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Fine-scale Relocation of Aftershock
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−43.25°OXZ0 10 20km−43.5°−4
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A’0 km 4 8−43.5°B’B−43.6°
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REFERENCESAvery, H. R., J. B. Berri
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▲ ▲ Figure 2. A) shows three-co
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▲ ▲ Figure 4. Vertical accelera
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0.8PRPC Z0.40Normalized (Max PGA +
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Near-source Strong Ground MotionsOb
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(A)Magnitude, M w876542009 NZdataba
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Scale0.5 g5 seconds▲▲Figure 4.
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(A)(B)Spectral Acc, Sa (g)North/Wes
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Vertical-to-horizontal PGA ratio543
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(A)(B)Station:CCCCSolid:AvgHorizDas
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REFERENCESAagaard, B. T., J. F. Hal
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Spectral Acceleration (0.3 s), (g)I
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Spectral Acceleration (3 s), (g)In[
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TABLE 1Mean (μ LLH ) and standard
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Strong Ground Motions and Damage Co
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ings and the Modified Takeda-Slip M
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high, but there were no buildings d
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REFERENCES▲▲Figure 8. Heavily d
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(A)(B)(C)(D)(E)▲▲Figure 1. A) M
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(A) (B) (C)▲ ▲ Figure 3. A) Typ
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Case StudyKey ParametersTABLE 1Key
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Soil Liquefaction Effects in the Ce
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Location of structures illustrated
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Shading indicates areaover which pr
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1.8 deg15 cmGround cracking due to
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30 cm17 cm30 cmFoundation beam▲
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Comparison of Liquefaction Features
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(A)(B)▲▲Figure 2. A) Simplified
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(A)Acceleration (Gal)6004002000-200
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