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only minor damage, mostly to their approaches. Outside theCBD, the two remaining bridges along the Avon that did notsuffer moderate or severe damage had only minor approachdamage. Compared to the Avon River, bridges crossing theHeathcote River sustained much less damage despite beingclose to the fault rupture, primarily due to the larger seismicresistance of the foundation soils of these bridges. Apart fromthree cases, all bridges along the Heathcote River were eitherundamaged or developed only minor approach damage.Eight road bridges suffered moderate damage followingthe 4 September 2010 Darfield earthquake, with five of theseclosed for five days or longer. Traffic weight limitations and/orrestricted lane access was in place for a more extended period,all but one of which instances was due to approach damage as aresult of lateral spreading. The Darfield earthquake had a largermagnitude, and thus resulting ground motions affected a muchlarger region, with bridge damage occurring from Lincoln, 15km south of central Christchurch, to Kaiapoi, 16 km north.The most distant bridge damage, at the Williams Street Bridgein Kaiapoi due to lateral spreading, was approximately 30 kmfrom the rupture of the Greendale fault. Within Christchurchcity itself, Gayhurst Road Bridge and South Brighton Bridgeboth experienced moderate damage, principally as a consequenceof lateral spreading (Allen et al. 2010; Palermo et al.2010).DAMAGE ASSOCIATED WITH LIQUEFACTIONBridges along both the Avon and Heathcote rivers sufferedvarying levels of damage from lateral spreading due to theDarfield and Christchurch earthquakes, with ground conditionsand distance from the epicenter influencing this responseas described previously. Even at a given bridge location the levelof damage varied significantly from one end of the bridge to theother, with more damage observed on the inner banks of thelocal river bends, likely a result of the low-energy depositionalenvironment, as compared to the outer banks. In this sectionof the paper, we present an overview on the heavily damagedFerrymead Bridge at the mouth of the Heathcote River andon the most affected bridges along the Avon River from theChristchurch earthquake.The type of bridge damage along the Avon was fairly consistent:settlement and lateral spreading of approaches, backrotationand cracking of the abutments, and some pier damage.In most cases bridge decks restrained movement of the top ofthe abutment, resulting in their back-rotation. There was littlebridge superstructure damage, with only minor crushing andspalling as a result of pounding and relative movement. Unlessotherwise noted, simply supported bridges discussed hereindid not have any bearings. All the damaged bridges previouslymentioned had pile foundations, with lateral spreading forcesplacing large demands on the abutment piles and likely resultingin plastic hinging below grade. The approach fill of severalbridges subsided by up to a meter, resulting in the bridges beingclosed up to a week. In most cases, settlement and spreading ofthe approaches impacted bridge serviceability.The Christchurch CBD bridges crossing the Avon Rivergenerally performed well, with the most common damagebeing minor lateral spreading, compression or slight slumpingof approach material, and minor cracking in abutments.All bridges were single span and were passable to recoveryvehicles in the cordon soon after the event. (The cordon isthe restricted-access area of the CBD, put in place due to thewidespread earthquake damage in the area.) Compared to theAvon River, bridges crossing the Heathcote suffered muchless damage. Apart from the Ferrymead Bridge at the mouthof the Heathcote, all bridges were either undamaged or experiencedonly minor damage. As previously noted, we inferthat this is the result of more resistant foundation soils alongthe Heathcote River relative to the Avon River. Typical damagewas minor approach settlement, with little impact on thebridge abutments and superstructure.Detailed descriptions of the bridges shown in Figure 4with the most severe liquefaction-induced damage and theanalyses of in situ test data at these sites follow. The PGAsused in the liquefaction evaluations were estimated using theground motion prediction equations of Bradley (2010) andthe spatial correlation model of Goda and Hong (2008). Theestimated PGAs at the bridge sites are the geometric mean ofthe two horizontal components for site class D (Standards NewZealand 2004) and are summarized in Table 1. Further informationon the calculation of these PGA values can be found inGreen et al. (2011, page 927 of this issue).Ferrymead BridgeThe Ferrymead Bridge (Figure 4A) was constructed in 1967,runs in the east-west direction, and spans the mouth ofHeathcote River (Figure 2). The bridge is a three-span reinforcedconcrete bridge supported by wall abutments withwingwalls and two four-column bents connected to pile caps.The west abutment and bents are supported by floating pilefoundations, while the eastern bent is supported by end-bearingpile foundations to bedrock, and the east abutment on shallowfoundations on bedrock.Although the Ferrymead Bridge performed well duringthe 2010 Darfield earthquake, at the time of the Christchurchearthquake it was undergoing a major upgrade to includewidening and underpinning of the deck with two reinforcedconcrete girders supported on two drilled shaft foundations.These upgrades had been planned before the occurrence of theDarfield earthquake. One of the girders at the east abutmenthad been completed and the girder at the west abutment waspartly completed when the Christchurch earthquake struck.Also, to allow access for construction cranes and equipment,two temporary steel bridges were erected on both sides of thebridge and were in place at the time of the Christchurch earthquake.Each abutment consisted of two separate sections, one infront of the other (i.e., one section supporting the superstructureand the other abutment block behind it). Lateral spreadingoccurred at the east abutment, with the material overlying thebedrock moving both perpendicular and parallel to the bridgeSeismological Research Letters Volume 82, Number 6 November/December 2011 953