The influence of off-fault deformation zones on the near-fault distribution of coseismic landslides

Bloom, Colin; Howell, Andrew; Stahl, Timothy; Massey, Chris; Singeisen, Corinne

doi:10.1130/g49429.1

Cited by 18 publications

(8 citation statements)

References 31 publications

(39 reference statements)

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“…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%

“…The earthquake ruptured faults of both the North Canterbury and the Marlborough Fault System tectonic domains (Figure 1, Litchfield et al, 2018) and caused complex surface deformation along c. 110 km of coastline (Clark et al, 2017). The earthquake generated more than 30,000 landslides which were primarily concentrated within the steep slopes of the Seaward Kaikōura range, around surface fault ruptures, and in steep sections of coastline (Figure 1 and 2; Massey et al, 2018Massey et al, , 2020aBloom et al, 2022a). Statistical modelling by Massey et al (2018Massey et al ( , 2020a found that the regional distribution of landslides from the Kaikōura earthquake was well explained by geology, slope, distance to surface fault traces, peak ground velocity (PGV), local slope relief, and elevation.…”

Section: Introductionmentioning

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: Factors Controlling Increased Coastal Landslide Densitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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show abstract

“…The amount of rock mass damage along with the absence of healed (i.e., veined or cemented) joints observed in the borehole furthermore suggest that healing processes at this site do not play a significant role over the time periods between strong ground-shaking events (approximately every few hundred years at this site). Furthermore, past coastal erosion has likely steepened the Half Moon Bay site and contributed to landslide development (Bloom et al, 2023).…”

Section: Landslide Failure Complex Evolutionmentioning

confidence: 99%

Evolution of an earthquake-induced landslide complex in the South Island of New Zealand: How fault damage zones and seismicity contribute to slope failures

Singeisen,

Massey,

Wolter

et al. 2023

Geosphere

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Tectonic deformation within fault damage zones can influence slope stability and landslide failure mechanisms due to rock mass strength effects and the presence of tectonic structures. Here, we used detailed site investigations to evaluate controls on deformation within the Half Moon Bay landslide complex, located ~1 km from the surface trace of the Hope fault in the South Island of New Zealand. During the 2016 Mw 7.8 Kaikōura earthquake, the slope experienced up to ~13 m of displacement and partially transitioned into a rock avalanche (with a volume of ~350,000 m3). Deep-seated deformation of the entire slope predated the 2016 earthquake. Results of geomorphological analysis, field mapping, geophysical surveys, slope displacement, and a 60-m-deep borehole in the incipient portion of the landslide indicated the presence of a subvertical tectonic fabric and intense fracturing and weathering of the rock mass, which gradually decrease with depth. Based on these results, we established a conceptual model wherein the landslide failure mechanism is a combination of flexural toppling along the subvertical structures coupled with joint-step-path sliding along preexisting, closely spaced discontinuities within the graywacke rock mass. Coseismic slope displacements revealed a large area of incipient failure behind the headscarp of the 2016 rock avalanche, which will likely result in further avalanching at the site. This case study demonstrates that inherited tectonic structures (combined with seismicity and weathering in an oversteepened coastal slope) play an important role in the evolution of hillslopes near active faults.

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“…2A ) ( 14 ). Oblique left-lateral reverse displacement produced some of the largest offsets recorded in the Kaikōura event ( 31 , 33 ), with the Papatea fault scarp displacing the Waiau Toa/Clarence River in four locations in an area referred to as Priam’s flat ( Fig. 2B ).…”

Section: Introductionmentioning

confidence: 99%

“…Excellent pre- and post-event data covering the Papatea fault rupture and associated avulsion provided an opportunity to analyze FIRA variables in more detail. Landscape change was captured through multitemporal lidar and allowed us to measure high-resolution near-field displacements ( 33 , 34 ). River discharge of 187 m 3 s −1 was recorded by an Environment Canterbury gauge attached to Glen Alton Bridge ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Coseismic river avulsion on surface rupturing faults: Assessing earthquake-induced flood hazard

et al. 2023

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Surface-rupturing earthquakes can produce fault displacements that abruptly alter the established course of rivers. Several notable examples of fault rupture–induced river avulsions (FIRAs) have been documented, yet the factors influencing these phenomena have not been examined in detail. Here, we use a recent case study from New Zealand’s 2016 Kaikōura earthquake to model the coseismic avulsion of a major braided river subjected to ~7-m vertical and ~4-m horizontal offset. We demonstrate that the salient characteristics of the avulsion can be reproduced with high accuracy by running a simple two-dimensional hydrodynamic model on synthetic (pre-earthquake) and “real” (post-earthquake) deformed lidar datasets. With adequate hydraulic inputs, deterministic and probabilistic hazard models can be precompiled for fault-river intersections to improve multihazard planning. Flood hazard models that ignore present and potential future fault deformation may underestimate the extent, frequency, and severity of inundation following large earthquakes.

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The influence of off-fault deformation zones on the near-fault distribution of coseismic landslides

Cited by 18 publications

References 31 publications

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

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

Evolution of an earthquake-induced landslide complex in the South Island of New Zealand: How fault damage zones and seismicity contribute to slope failures

Coseismic river avulsion on surface rupturing faults: Assessing earthquake-induced flood hazard

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