Geotechnical aspects of the 2016 Kaikōura earthquake on the South Island of New Zealand

Abstract

The magnitude Mw7.8 ‘Kaikōura’ earthquake occurred shortly after midnight on 14 November 2016. This paper presents an overview of the geotechnical impacts on the South Island of New Zealand recorded during the post-event reconnaissance.
 Despite the large moment magnitude of this earthquake, relatively little liquefaction was observed across the South Island, with the only severe manifestation occurring in the young, loose alluvial deposits in the floodplains of the Wairau and Opaoa Rivers near Blenheim. The spatial extent and volume of liquefaction ejecta across South Island is significantly less than that observed in Christchurch during the 2010-2011 Canterbury Earthquake Sequence, and the impact of its occurrence to the built environment was largely negligible on account of the severe manifestations occurring away from the areas of major development.
 Large localised lateral displacements occurred in Kaikōura around Lyell Creek. The soft fine-grained material in the upper portions of the soil profile and the free face at the creek channel were responsible for the accumulation of displacement during the ground shaking. These movements had severely impacted the houses which were built close (within the zone of large displacement) to Lyell Creek. The wastewater treatment facility located just north of Kaikōura also suffered tears in the liners of the oxidation ponds and distortions in the aeration system due to ground movements.
 Ground failures on the Amuri and Emu Plains (within the Waiau Valley) were small considering the large peak accelerations (in excess of 1g) experienced in the area. Minor to moderate lateral spreading and ejecta was observed at some bridge crossings in the area. However, most of the structural damage sustained by the bridges was a result of the inertial loading, and the damage resulting from geotechnical issues were secondary.

Resilience and fragility of the telecommunication network to seismic events

“…No damage was observed to access pits that are normally very small in the rural areas; there was no damage to manholes located in Kaikōura town, where little liquefaction induced was observed [19]. After the Canterbury earthquake sequence 2010-2011, key damage to manholes and access pits was generally due to permanent ground movements and liquefaction, causing manholes to floating or be filled with ejected material [5].…”

Performance of road bridges during the 14 November 2016 Kaikōura Earthquake

“…It is believed that the flattening of the tunnel lining on the southwest side was due to settlement of the fill on the southeast side causing unbalanced lateral earth pressure which the flexible lining could not sustain resulting in permanent deformation. More geotechnical details are reported in Stringer et al [4].…”

“…The manner of the tilt was such that the bottom of the pier D appeared to have moved towards the waterway. The mode of cracking of the piers and abutments (over the entire width of the bridge) ( Figure 29d) indicates that lateral spreading effects were significant at this bridge [4]. The Waima River (Ure) ( Figure 30a) and Waima Overbridge (Figure 30b) were constructed in 1975 and 1985, respectively, and are located just over 1km apart on SH1.…”

“…The observations in this paper are focused more on structural damage, however, basic descriptions of geotechnical and utility damage are also presented to provide a complete picture of the observed damage related to bridges and their approaches. More details regarding geotechnical observations from the Kaikōura Earthquake can be found in Stringer et al [4]. Of the bridges inspected, several displayed interesting and also complex damage patterns and for four of those bridges, simplified, damage schematics are provided to show the distribution of damage and indicate their response during the earthquake.…”

GIS-based microzonation for liquefaction-induced ground damage in Auckland Region

“…In geotechnical engineering, an important aspect of the seismic design process is the assessment of the potential for liquefaction-induced ground damage. Consequences of liquefaction may prove to be costly and severe, as was seen in 2010-11 Canterbury earthquake sequence (Cubrinovski et al, 2011) and the 2016 Kaikōura earthquake (Cubrinovski et al 2017, Stringer et al 2017). Regional assessment of liquefaction susceptibility was last undertaken in 1997 as part of the Auckland Engineering Lifelines Project -Stage 1 (ARC 1997), prior to the recent advancements in the understanding and assessment of liquefaction susceptibility and surface manifestation severity.…”