Mechanisms of rock slope failures triggered by the 2016 Mw 7.8 Kaikōura earthquake and implications for landslide susceptibility

Singeisen, Corinne; Massey, Chris; Wolter, Andrea; Kellett, Richard; Bloom, Colin; Stahl, Timothy; Gasston, Caleb; Jones, Katie

doi:10.1016/j.geomorph.2022.108386

Cited by 18 publications

(28 citation statements)

References 55 publications

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“…Previous investigations (e.g., Marc et al, 2015Marc et al, , 2019Massey et al, 2022) suggest that increased landslide susceptibility decays to background levels within several years of an earthquake. It may be possible, however, that the factors discussed in this study, including oversteepened hillslopes, fault deformation, coastal weathering, and repeated earthquake shaking, contribute to an accumulation of stress within the hillslope and, in turn, longer term susceptibility to extreme event failure (Parker et al, 2015).…”

Section: Implications For Earthquake Induced Landslide Susceptibility...mentioning

confidence: 93%

“…The predictive power of individual landslide susceptibility features during the Kaikōura earthquake was strongly modulated by geology type (Massey et al, 2018(Massey et al, , 2020aSingeisen et al, 2022). Separate coastal (0 to 1 km from the coast) and inland (1 to 3 km from the coast) models were, therefore, trained in four simplified geology types (GeolCodes 1, 2, 3, and 5; Figure 3) using predictive features and the sci-kit learn python library (Table 1).…”

Section: Logistic Regression Modellingmentioning

confidence: 99%

“…Topographic and site amplification of seismic waves (e.g., Ashford et al, 1997) likely contributed to local variability in strong ground motion intensity within individual coastal and inland hillslopes during the Kaikōura earthquake. Ground motion variability is known to influence landslide susceptibility (e.g., Massey et al, 2022) but remains challenging to estimate on a regional scale. Outside of applying regional ground motion intensity estimates (PGA/PGV from the USGS ShakeMap), this analysis does not investigate the role of site-specific ground motion.…”

Section: Factors Controlling Increased Coastal Landslide Densitymentioning

confidence: 99%

“…However, hillslopes within the heavily deformed GeolCode 5 may be susceptible to failure regardless of the presence of persistent structural discontinuity. In the heavily jointed rock mass, debris and rock avalanches, the dominant failure mechanism along the Kaikōura coast, can develop along cm-to m-scale discontinuities (Singeisen et al, 2022) that are not captured by the estimation of larger scale bedding. Furthermore, field investigations along the Kaikōura coast (e.g., Stringer et al, 2021) have shown that many failures from the 2016 earthquake, particularly in mapped GeolCode 5, occurred as reactivations of pre-existing landslide debris or within Quaternary hillslope deposits that were unlikely to be strongly influenced by bedding orientation.…”

Section: Factors Controlling Increased Coastal Landslide Densitymentioning

confidence: 99%

“…This being said, there is still some ambiguity as to the influence of rock mass deformation from fault zones along the coast that did not rupture significantly in 2016; for example, the Hope fault which extends just offshore in parallel to much of the north Kaikōura coast. A history of strong ground motion and fault deformation has been shown to progressively decrease rock mass strength and increase landslide susceptibility over multiple earthquakes (Parker et al, 2015;Gischig et al, 2016;Bloom et al, 2022a;Massey et al, 2022). This may result in an increased landslide susceptibility due to amplification of strong ground motion and decreased rock mass strength.…”

Section: Factors Controlling Increased Coastal Landslide Densitymentioning

confidence: 99%

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Coastal earthquake induced landslide susceptibility during the 2016 Mw 7.8 Kaikōura earthquake, New Zealand

Bloom

Singeisen

Stahl

et al. 2023

Preprint

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Abstract. Coastal hillslopes often host higher concentrations of earthquake induced landslides than those further inland, but few studies have investigated the reasons for this occurrence. As a result, it remains largely unclear if regional earthquake induced landslide susceptibility models trained primarily on inland hillslopes are effective predictors of coastal susceptibility. The 2016 Mw 7.8 Kaikōura earthquake on the northeast South Island of New Zealand resulted in c. 1,600 landslides > 50 m2 on slopes > 15° within 1 km of the coast. This forms an order of magnitude greater landslide source area density than inland hillslopes within 1 to 3 km of the coast. In this study, the distribution of regionally predictive landslide susceptibility variables, or features, and logistic regression modelling are used to investigate how landslide susceptibility differs between coastal and inland hillslopes and determine the factors that drive the distribution of coastal landslides initiated by the 2016 Kaikōura earthquake. Strong model performance (Area under the Receiver Operator Characteristic Curve or AUC of c. 0.80 to 0.92) was observed across eight models, which adopt four simplified geology types. The same landslide susceptibility factors, primarily geology, steep slopes, and ground motion are strong model predictors for both inland and coastal landslide susceptibility in the Kaikōura region. In three geology types (which account for more than 90 % of landslides source areas) a 0.03 or less drop in model AUC is observed when predicting coastal landslides using inland trained models. This suggests little difference between the features driving inland and coastal landslide susceptibility in the Kaikōura region. Geology is similarly distributed between inland and coastal hillslopes and PGA is generally lower in coastal hillslopes. Slope angle, however, is significantly higher in coastal hillslopes and provides the best explanation for the high density of coastal landslides during the 2016 Kaikōura earthquake. Existing regional earthquake induced landslide susceptibility models trained on inland hillslopes using common predictive features are likely to capture this signal. Interestingly, in the Kaikōura region, most coastal hillslopes are isolated from the ocean by uplifted shore platforms. Enhanced coastal landslide susceptibility from this event appears to be a legacy effect of past active erosion, which preferentially steepened these coastal hillslopes.

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Section: Implications For Earthquake Induced Landslide Susceptibility...mentioning

confidence: 93%

Section: Logistic Regression Modellingmentioning

confidence: 99%

Section: Factors Controlling Increased Coastal Landslide Densitymentioning

confidence: 99%

Section: Factors Controlling Increased Coastal Landslide Densitymentioning

confidence: 99%