Geomorphological Influences on the Distribution of Liquefaction in the Wairau Plains, New Zealand, Following the 2016 Kaikoura Earthquake

The 2016 M-w 7.8 Kaikoura earthquake triggered localized liquefaction and associated lateral spreading in the Wairau Plains on the South Island of New Zealand. Detailed postevent mapping from ground and helicopter-based reconnaissance indicates that liquefaction predominantly manifested proximal to rivers and streams within the easternmost extent of the plains. In this study, pre- and postevent light detection and ranging (lidar) survey data and aerial photography are analyzed to further resolve maximum extents of liquefaction-induced damage and to infer the presence and/or absence of liquefaction in areas that were not covered during reconnaissance surveys. Historical maps used in conjunction with local geomorphologic and topographic variability are shown to provide insights into the depositional settings of areas where liquefaction manifestations were observed. Cone penetration test (CPT) logs are additionally utilized to examine characteristics of the subsurface soil profiles in areas where liquefaction did and did not manifest. The various data sources indicate that the observed distributions of liquefaction manifestations within the lower Wairau Plains correlate with basic depositional processes of meandering rivers and correspond with the position of point-bar and paleochannel deposits. This study highlights the potential applications and benefits of incorporating geomorphic and topographic variability into liquefaction hazard assessments.