Christchurch, New Zealand, experienced four major earthquakes (Mw 5.9 to 7.1) since 4 September 2010 that triggered localized to widespread liquefaction. Liquefaction caused significant damage to residential foundations due to ground subsidence, ground failure, and lateral spreading. This paper describes the land damage assessment process for Christchurch, including the collection and processing of extensive data and observations related to liquefaction, the characterization of liquefaction effects on land performance, and the quantification of losses for insurance compensation purposes. The paper also examines the effectiveness of several existing liquefaction vulnerability parameters and a new parameter developed through this research, Liquefaction Severity Number ( LSN), in explaining the observed liquefaction-induced damage in residential areas of Christchurch using results from 11,500 cone penetration tests (CPTs) as well as a robust regional groundwater model.

a b s t r a c tSeismic shaking and tectonic deformation during strong earthquakes can trigger widespread environmental effects. The severity and extent of a given effect relates to the characteristics of the causative earthquake and the intrinsic properties of the affected media. Documentation of earthquake environmental effects in wellinstrumented, historical earthquakes can enable seismologic triggering thresholds to be estimated across a spectrum of geologic, topographic and hydrologic site conditions, and implemented into seismic hazard assessments, geotechnical engineering designs, palaeoseismic interpretations, and forecasts of the impacts of future earthquakes. The 2010-2011 Canterbury Earthquake Sequence (CES), including the moment magnitude (M w ) 7.1 Darfield earthquake and M w 6.2, 6.0, 5.9, and 5.8 aftershocks, occurred on a suite of previously unidentified, primarily blind, active faults in the eastern South Island of New Zealand. The CES is one of Earth's best recorded historical earthquake sequences. The location of the CES proximal to and beneath a major urban centre enabled rapid and detailed collection of vast amounts of field, geospatial, geotechnical, hydrologic, biologic, and seismologic data, and allowed incremental and cumulative environmental responses to seismic forcing to be documented throughout a protracted earthquake sequence. The CES caused multiple instances of tectonic surface deformation (≥3 events), surface manifestations of liquefaction (≥11 events), lateral spreading (≥6 events), rockfall (≥6 events), cliff collapse (≥3 events), subsidence (≥4 events), and hydrological (10s of events) and biological shifts (≥3 events). The terrestrial area affected by strong shaking (e.g. peak ground acceleration (PGA) ≥0.1-0.3 g), and the maximum distances between earthquake rupture and environmental response (R rup ), both generally increased with increased earthquake M w , but were also influenced by earthquake location and source characteristics. However, the severity of a given environmental response at any given site related predominantly to ground shaking characteristics (PGA, peak ground velocities) and site conditions (water table depth, soil type, geomorphic and topographic setting) rather than earthquake M w . In most cases, the most severe liquefaction, rockfall, cliff collapse, subsidence, flooding, tree damage, and biologic habitat changes were triggered by proximal, moderate magnitude (M w ≤ 6.2) earthquakes on blind faults. CES environmental effects will be incompletely preserved in the geologic record and variably diagnostic of spatial and temporal earthquake clustering. Liquefaction feeder dikes in areas of severe and recurrent liquefaction will provide the best preserved and potentially most diagnostic CES features. Rockfall talus deposits and boulders will be well preserved and potentially diagnostic of the strong intensity of CES shaking, but challenging to decipher in terms of single versus multiple events. Most other phenomena will be transient (e.g., distal groundwater r...

This paper explores key aspects of underground pipeline network response to the Canterbury earthquake sequence in Christchurch, New Zealand, including the response of the water and wastewater distribution systems to the MW6.2 22 February 2011 and MW6.0 13 June 2011 earthquakes, and the response of the gas distribution system to the MW7.1 4 September 2010 earthquake, as well as the 22 February and 13 June events. Repair rates, expressed as repairs/km, for different types of pipelines are evaluated relative to (1) the spatial distribution of peak ground velocity outside liquefaction areas and (2) the differential ground surface settlement and lateral ground strain within areas affected by liquefaction, calculated from high-resolution LiDAR survey data acquired before and after each main seismic event. The excellent performance of the gas distribution network is the result of highly ductile polyethylene pipelines. Lessons learned regarding the earthquake performance of underground lifeline systems are summarized.

System response refers to the consideration of the soil deposit as a system of layers interacting with each other in their dynamic response (e.g. liquefaction effects on the ground motion) and through pore water pressure redistribution and water flow (e.g. seepage effects) [1]. The present study examines key factors affecting the triggering of system response mechanisms and their contribution to liquefaction-induced damage.

Airborne light detection and ranging (LiDAR) data were acquired over the coastal city of Christchurch, New Zealand, prior to and throughout the 2010 to 2011 Canterbury Earthquake Sequence. Differencing of pre-and post-earthquake LiDAR data reveals land surface and waterway deformation due to seismic shaking and tectonic displacements above blind faults. Shaking caused floodplain subsidence in excess of 0.5 to 1 m along tidal stretches of the two main urban rivers, greatly enhancing the spatial extent and severity of inundation hazards posed by 100-year floods, storm surges, and sea-level rise. Additional shaking effects included river channel narrowing and shallowing, due primarily to liquefaction, and lateral spreading and sedimentation, which further increased flood hazard. Differential tectonic movement and associated narrowing of downstream river channels decreased channel gradients and volumetric capacities and increased upstream flood hazards. Flood mitigation along the large regional Waimakariri River north of Christchurch may have, paradoxically, increased the long-term flood hazard in the city by halting long-term aggradation of the alluvial plain upon which Christchurch is situated. Our findings highlight the potential for moderate magnitude (MW 6-7) earthquakes to cause major topographic changes that influence flood hazard in coastal settings.