Landslides and surface fault rupture from the Mw 7.8 2016 Kaikōura Earthquake
Large volume (>106 m3) earthquake-induced landslides (EILs) are a hazard that can result in both catastrophic damage to the natural and built environment, and the loss of human life. However, EILs are not well studied and there is a limited understanding of controls on the exact triggering mechanisms. The interaction between site controls and the seismological characteristics of the triggering earthquake are of particular interest, because understanding these can help to refine EIL risk and susceptibility models, which at present are inadequate to predict the occurrence of large EILs. The Mw 7.8 2016 Kaikoura Earthquake, New Zealand, provides a unique opportunity to study the site and seismological factors that contribute to failure of large EILs. Herein, I present the results of field, remote sensing, and 3D modelling studies of the four largest EILs triggered by the Mw 7.8 2016 Kaikoura Earthquake. No one single factor was found to control the initiation of failure or the observed distribution of large volume EILs. Indeed, it was the complex interaction of multiple factors that initiated failure. It was found that active faults form site conditions that are conducive to the initiation of large volume EILs. The presence of an active fault through the source area, and the dynamic component of near-fault, pulse-like ground motions were more important for triggering large landslides during the Kaikōura Earthquake, than the magnitude of permanent displacement associated with fault surface rupture. No correlation between the magnitude of fault surface rupture and the magnitude of slope failure was observed. Historic instability at the sites was found to be an important control on large EIL occurrence for the Kaikoura Earthquake. Kinematic feasibility of defects was found to be less important when extreme dynamic loads are considered, and this has implications for site assessments. Volumes for the four study sites were estimated using 3D modelling and were found not to fit with commonly used lanThis research has defined how site controls interacted with fault surface rupture and ground shaking to initiate large volume landslides during the Mw 7.8 Kaikoura Earthquake. The controls defined here were found to be non-unique and should be used for future hazard/risk modelling and site assessment.dslide area-volume scaling relationships.
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