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Potential geomorphic consequences of a future Great (Mw 8.0+) Alpine Fault earthquake, South Island, New Zealand
Natural Hazards and Earth System Sciences
Abstract and Figures
The Alpine fault in New Zealand's South Island has not sustained a large
magnitude earthquake since c. AD 1717. The time since this rupture (295
years) is close to the average inferred recurrence interval of the fault
(~300 years) and the Alpine fault is therefore expected to generate a
large magnitude earthquake in the near future. Previous ruptures of this
fault are inferred to have generated Mw 8.0 or greater earthquakes and
to have generated, amongst other geomorphic hazards, large-scale
landsliding and landslide dams throughout the Southern Alps. There is
currently 85% probability that the Alpine fault will cause a Mw 8.0+
earthquake within the next 100 years. While the seismic hazard is fairly
well understood, that of the consequential geomorphic activity is less
well-studied, and these consequences are explored herein. They are
expected to include landsliding, landslide damming, dambreak flooding,
debris flows, river aggradation, liquefaction, and landslide-generated
lake/fiord tsunami. Using evidence from previous events within New
Zealand as well as analogous international examples we develop
first-order estimates of the likely magnitude and possible locations of
the geomorphic effects associated with earthquakes. Landsliding is
expected to affect an area >30,000 square kilometres and involve
>1 billion cubic metres of material. Landslide dams are expected to
occur in many narrow, steep-sided gorges in the affected region. Debris
flows will be generated in the first long-duration rainfall after the
earthquake and will continue to occur for several years as rainfall
(re)mobilises landslide material. In total more than 1000 debris flows
are likely to be generated at some time after the earthquake.
Aggradation of up to 3 m will cover an area >125 square kilometres
and is likely to occur on many West Coast alluvial fans. The impact of
these effects will be felt across the entire South Island and are likely
to continue for several decades.
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... Area of Figure 12 is shown as a red rectangle. Source: This work includes Toit u Te Whenua Land Information New Zealand data, which are licensed by Toit u Te Whenua Land Information New Zealand for re-use under the Creative Commons Attribution 4.0 International licence [Color figure can be viewed at wileyonlinelibrary.com] in alpine sections of the river (Robinson & Davies, 2013;Wells & Goff, 2006) and (2) flooding and sedimentation-induced damage to farms and property, and infrastructural lifelines (Orchiston et al., 2018). Most of the understanding of related sediment fluxes is based on (1) decadal landslide inventories in the Southern Alps (Hovius et al., 1997); (2) experience from non-earthquake-related landslides in individual catchments (e.g., Korup, 2005); and (3) volumes of landslidegenerated sediment from elsewhere in New Zealand or globally, calibrated against modern sediment loads and an assumption of steady state processes in the Southern Alps where denudation balances mountain building. ...
... (2013) of 2-4 m and assume no sediment bypass in the calculation. It is likely that the catchments of the range front fans generate disproportionately high yields compared with the region-wide average sediment yields proposed by Robinson and Davies (2013) because of their proximity to the fault, steeper than average slopes and weak cataclastic rocks. Our 95% CI estimates of the duration of the relaxation phase (duration of aggradation) range from effectively instantaneous to nearly two centuries based on OxCal models (Table 2) These average rates obscure the likely punctuated and locally thick sedimentation that would make maintaining pasture and farm infrastructure impossible, as demonstrated by the Poerua River aggradation following the 1999 Mt Adams landslide (Davies & Korup, 2007). ...
... Blagen et al. (2022) suggest that this effect may lead to less aggradation at fan heads and more towards fan toes, with a more rapid progression of aggradation down-fan. Robinson and Davies (2013) noted that few alluvial fans are currently aggrading and that most fan heads are incised, as we see at the Te Taho fans. Therefore, most West Coast alluvial fans responding to Alpine Fault earthquakes are likely to have relatively short response times as Davies and Korup (2007) (Wang et al., 2017). ...
We examined the stratigraphy of alluvial fans formed at the steep range front of the Southern Alps at Te Taho, on the north bank of the Whataroa River in central West Coast, South Island, New Zealand. The range front coincides with the Alpine Fault, an Australian-Pacific plate boundary fault, which produces regular earthquakes. Our study of range front fans revealed aggradation at 100- to 300-year intervals. Radio- carbon ages and soil residence times (SRTs) estimated by a quantitative profile devel- opment index allowed us to elucidate the characteristics of four episodes of aggradation since 1000 CE. We postulate a repeating mode of fan behaviour (fan response cycle [FRC]) linked to earthquake cycles via earthquake-triggered land- slides. FRCs are characterised by short response time (aggradation followed by inci- sion) and a long phase when channels are entrenched and fan surfaces are stable (persistence time). Currently, the Te Taho and Whataroa River fans are in the latter phase. The four episodes of fan building we determined from an OxCal sequence model correlate to Alpine Fault earthquakes (or other subsidiary events) and support prior landscape evolution studies indicating ≥M7.5 earthquakes as the main driver of episodic sedimentation. Our findings are consistent with other historic non- earthquake events on the West Coast but indicate faster responses than other earth- quake sites in New Zealand and elsewhere where rainfall and stream gradients (the basis for stream power) are lower. Judging from the thickness of fan deposits and the short response times, we conclude that pastoral farming (current land-use) on the fans and probably across much of the Whataroa River fan would be impossible for several decades after a major earthquake. The sustainability of regional tourism and agriculture is at risk, more so because of the vulnerability of the single through road in the region (State Highway 6).
... Anthropogenic interactions including rapid infrastructure development (Petley et al. 2007) in combination with ground shaking becomes a major triggering factor for landslide occurrence (Süzen and Kaya 2012) in mountainous region (Robinson et al. 2017). In this regards, detailed analysis of earthquake-triggered landslide following an earthquake supplements the knowledge to understand the total impact of the earthquake (Marzorati et al. 2002;Robinson and Davies 2013). Landslide susceptibility mapping (LSM) identifies landslide sensitive areas considering the relationship between causal factors and landslide (Fell et al. 2008), it is a key step for landslide hazard monitoring and mitigation (Pourghasemi and Rahmati 2018). ...
... Understanding overall impact of earthquake hazards require the understanding of several features of co-seismic landslide (Robinson and Davies 2013). It includes the landslide number, area, and volume (e.g., Keefer 1984;Marc et al. 2016) and the location of landslides (e.g., Dai et al. 2011). ...
The main objective of this study is to understand the overall impact of earthquake in upper Indrawati Watershed, located in the high mountainous region of Nepal. Hence, we have assessed the relationship between the co-seismic landslide and underlying causative factors as well as performed landslide susceptibility mapping (LSM) to identify the landslide susceptible zone in the study area. We assessed the landslides distribution in terms of density, number, and area within 85 classes of 13 causal factors including slope, aspect, elevation, formation, land cover, distance to road and river, soil type, total curvature, seismic intensity, topographic wetness index, distance to fault, and flow accumulation. The earthquake-induced landslide is clustered in Northern region of the study area, which is dominated by steep rocky slope, forested land, and low human density. Among the causal factors, 'slope' showed positive correlation for landslide occurrence. Increase in slope in the study area also escalates the landslide distribution, with highest density at 43%, landslide number at 4.34/km ² , and landslide area abundance at 2.97% in a slope class (> 50°). We used logistic regression (LR) for LSM integrating with geographic information system. LR analysis depicts that land cover is the best predictor followed by slope and distance to fault with higher positive coefficient values. LSM was validated by assessing the correctly classified landslides under susceptibility categories using area under curve (AUC) and seed cell area index (SCAI). The LSM approach showed good accuracy with respective AUC values for success rate and prediction rate of 0.843 and 0.832. Similarly, the decreasing SCAI value from very low to very high susceptibility categories advise satisfactory accuracy of the LSM approach.
... Random Forest is a machine learning technique for group learning [37,38]. Based on bootstrap samples, a decision tree was built. ...
Earthquake-induced landslides are one of the most dangerous secondary disasters in mountainous areas throughout the world. The nowcasting of coseismic landslides is crucial for planning land management, development, and urbanization in mountainous areas. Taking Wenchuan County in Western Sichuan Plateau (WPS) as the study area, a landslide inventory was built using historical records. Herein, eight causative factors were selected for a library of factors, and then a landslide susceptibility assessment (LSA) was performed based on the machine learning techniques of Random Forest (RF) and Artificial Neural Network (ANN) models, respectively. The prediction abilities of the above two LSM models were assessed using the area under curve (AUC) value of the receiver operating characteristics (ROC) curve, precision, recall ratio, accuracy, and specificity. The performances of both machine learning techniques were found to be excellent, but RF outperformed in accuracy. There were still some differences between the models’ performances shown by the results: RF (AUC = 0.966) outperformed ANN (AUC = 0.914). The RF model demonstrated a higher degree of correlation between the areas classified as very low and high susceptibility in comparison to the ANN model. The results provided a theoretical framework upon which machine learning applications could be applied (e.g., RF and ANN), a reliable and low-cost tool to assess landslide susceptibility. This comparative study will provide a useful description of earthquake-induced landslides in the study area, which can be used to anticipate the features of landslides in the future, and have played a very important role in proper anthropogenic activities, resource management, and infrastructural development of the mountainous areas.
... In addition, earthquakes can cause a large amount of landslide deposits to accumulate in channels or on slopes. Once these loose materials are transported from the slope to the channel, they are often transported out of the basin by debris flow, resulting in a series of geological hazards and geomorphic consequences (Fan et al., 2019;Robinson and Davies, 2013). Furthermore, catastrophic earthquakes can cause surface deformation, cracks and severe vegetation destruction, destabilizing the geological environment and leading to higher landslide activity in subsequent years or even decades Fan et al., 2019;Huang and Li, 2014;Koi et al., 2008;Wasowski et al., 2011;Xiong et al., 2020;Zhang and Zhang, 2017). ...
Approximately 200,000 landslides were triggered by the 2008 Wenchuan earthquake and subsequent strong rainfall events, and the amount of landslide sediment delivered to the channels within catchments depended on the amount of landslide debris generated by the earthquake and the amount of post-earthquake rainfall. To better understand long-term hillslope erosion and the long-term changes in landslide–channel coupling, this study quantifies the coupling degree of landslide–channel by defining a landslide-channel coupling index (LCCI) and estimates the long-term hillslope erosion driven by landslides within 12 debris flow basins. We track landslide activity using multiyear imagery from 2008 to 2019, and the landslide ratio, landslide new regeneration ratio, and landslide reactivated ratio indicate that the overall landslide activity decayed following the Wenchuan earthquake. The calculation results of the coupling index illustrate that the coupling degree of landslide–channel in the study area follows a power law trend of decay over time. However, due to the influence of landslide activity, the coupling index decreased significantly in the first 5 years after the Wenchuan earthquake and then decreased slowly. The hillslope erosion driven by landslides is estimated using a conservative statistical model. The result shows that the landslide-driven hillslope erosion has decayed following a power law, and elevated levels of erosion may last for an unexpectedly long period. In addition, the landslide–channel coupling degree affects the movement of landslide sediment to channels. While the coupling degree of landslide–channel and the amount of landslide sediment supplied to the channels have decreased significantly in recent years, abundant landslide sediment could still be delivered to the channels when strong rainfall occurs in this region. Furthermore, a considerable amount of sediment appears to remain within the tributary channels and trunk channels, which means the activity of debris flow may last longer period than hillslope erosion.
... Various geomorphological indexes have been proposed to quantify fault activity (Troiani and Seta 2008;Arrowsmith and Zielke 2009;Parul et al. 2013;Troiani et al. 2014;Gao et al. 2015;Liu et al. 2015;Liu and Du 2016;Kaushal et al. 2017;Wang et al. 2017;He et al. 2018;Pavano et al. 2018;Sharma et al. 2018;Wang et al. 2019). Terrain analysis of seismogenic faults has been well documented in studies areas around the world (Cello et al. 2000;Lin et al. 2003;Pucci et al. 2003;Maschio et al. 2005;Irikura 2012; Mahmood and Gloaguen 2012 ;Robinson and Davies 2013 ;Koukouvelas et al. 2018), and has become a major method for studying neotectonics, seismogeology, and paleoseismology (Papanikolaou et al. 2015). In addition, Noriega et al. (2006) and Chen et al. (2013) demonstrated that deflected streams can be used to compute fault slip rate in history by sediment dating on the offset stream channels. ...
This study presents geomorphic analysis of Xiadian buried fault in eastern Beijing plain (China), based on the analysis of a Satellite Pour l’Observation de la Terre (SPOT-5) image, a high-resolution digital elevation model (DEM) derived from an unmanned aerial vehicle (UAV) system, SRTM DEM and field investigation. Interpretations of the SPOT-5 image show that the pits always distribute between fault scarp segments or shallow grooves. The geomorphic features near the fault show echelon arrangements caused by dextral strike-slip activities of the fault. Based on this, the characteristics of stress field in this area have been clearly inferred. At centimeter-level accuracy, UAV-derived DEM profiles can clearly show micro tectonic landforms such as fault scarps, shallow grooves, steep slopes, and pits. Combined with previous research and field measurements, the evolution rates in length and height of the fault scarps are analysed. Furthermore, the deflection analysis of the drainage system also shows the characteristics of the continuous strike slip activity of the Xiadian fault. The study can provide valuable insight into geomorphic analysis of buried and semi-buried active faults in plain areas with increasingly frequent human activities.
... As identified in previous studies, the Franz Josef township is threatened by a number of hazards [7]. A review of existing studies and consultations with experts have identified several components of the disaster system in the Franz Josef area [9,11,13,[51][52][53][54][55][56]. The hazard elements used in the present modelling are earthquake shaking (due to the activity of the Alpine fault and other sources), rainfall, flooding from the Waiho river, landsliding, and landslide dam in the Callery catchment; while the potentially vulnerable elements are houses, roads and the stopbanks of the Waiho river. ...
Probabilistic multihazard risk assessment from natural hazard is still a challenge today. Current limitations are the number of different hazards that can be included in the assessment, the capacity to output detailed spatial results and access to data for inverse fitting models. A novel quantitative multi-hazard framework is proposed which permit to model the interactions and triggering of perils of different types. Franz Josef on the West Coast of South Island, New Zealand, is used as a case study where the interactions and impacts of earthquake, rainfall, landslide, landslide dam and flooding hazards on the road network, stopbanks and housing is stochastically quantified. The results show that losses are earthquake-dominated, while rarer events show an influence of landsliding on the losses. Due to the complex interaction between hazards allowed by the modelling framework, while initial perils reach a “loss ceiling” with reducing probabilities, it also supercharges secondary perils that can cause greater and greater losses. Combining a network framework with iterative simulations is shown to provide inherent advantages by its discrete nature. In-depth exploration of the data outputs grants insight into the interconnected disaster system on a granular level. The risk assessment herein pointed out the seriousness of the multihazard threat to the Franz Josef township.
We observed and further exhumed curved slickenlines on fault planes associated with paleo-surface rupture of the Alpine Fault, New Zealand’s ∼30 mm/yr continental transform plate boundary. Dynamic rupture modeling indicates that the geometry of such curvature provides a record of past earthquake rupture directions. We focused our efforts on three sites that span a region known to variably halt or allow passage of past earthquakes (an “earthquake gate”) to contribute rupture direction constraints to the fault’s spatiotemporally rich paleoseismic record. At Hokuri Creek and Martyr River, we observed both convex-up and convex-down curved slickenlines on and adjacent to principal slip surfaces, indicating past ruptures from both the northeast and southwest of these locations. At Martyr River, relationships suggest that the most recent event (inferred to correlate to 1717 CE) ruptured from the southwest. Our results demonstrate the utility of curved slickenlines as a valuable new paleoseismological tool for determining past rupture directions, applicable to surface-rupturing faults globally.
Coseismic landslides represent the first stage of a broader cascading sequence of geohazards associated with high‐magnitude continental earthquakes, with the subsequent remobilization of coseismic landslide debris posing a long‐term post‐seismic legacy in mountain regions. Here, we quantify the controls on the hazard posed by landslide remobilization and debris runout, and compare the overlap between areas at risk of runout and the pattern of post‐seismic landslides and debris flows that actually occurred. Focusing on the 2015 Mw 7.8 Gorkha earthquake in Nepal, we show that the extent of the area that could be affected by debris runout remained elevated above coseismic levels 4.5 years after the event. While 150 km² (0.6% of the study area) was directly impacted by landslides in the earthquake, an additional 614 km² (2.5%) was left at risk from debris runout, increasing to 777 km² (3.2%) after the 2019 monsoon. We evaluate how this area evolved by comparing modelled predictions of runout from coseismic landslides to multi‐temporal post‐seismic landslide inventories, and find that 14% (85 km²) of the total modelled potential runout area experienced landslide activity within 4.5 years after the earthquake. This value increases to 32% when modelled runout probability is thresholded, equivalent to 10 km² of realized runout from a remaining modelled area of 32 km². Although the proportion of the modelled runout area from coseismic landslides that remains a hazard has decreased through time, the overall runout susceptibility for the study area remains high. This indicates that runout potential is changing both spatially and temporally as a result of changes to the landslide distribution after the earthquake. These findings are particularly important for understanding evolving patterns of cascading hazards following large earthquakes, which is crucial for guiding decision‐making associated with post‐seismic recovery and reconstruction.
In the active tectonic setting of Aotearoa/New Zealand, large earthquakes are a relatively frequent occurrence and pose particular threats to infrastructure and society in Westland, on the west coast of South Island. In order to better define the medium- and long-term (annual to decadal) implications of these threats, existing dendrochronological data were supplemented by several hundred tree-ring analyses from 14 hitherto unstudied living tree stands in five catchments; these were combined to compile a regional picture of the location, extent, and timing of major prehistoric reforestation episodes on the floodplains of the area. These episodes correspond well with known dates of large earthquakes in the area (ca. 1400, ca. 1620, 1717 and 1826 AD), and their extents are thus interpreted to reflect the sediment deliveries resulting from coseismic landsliding into mountain valleys, and their reworking by rivers to generate widespread avulsion, aggradation, floodplain inundation and forest death. This regional aggradation picture can underpin anticipation of, and planning for, the medium- to long-term societal impacts of future major West Coast earthquakes. The source location of the next major earthquake in the region is unknown, so any of the Westland floodplains could be affected by extensive, up to metre-scale river aggradation, together with avulsion and flooding, in its aftermath, and these could continue for decades. Re-establishment and maintenance of a functioning economy under these conditions will be challenging because roads, settlements and agriculture are mostly located on the floodplains. The differences in floodplain vegetation between prehistoric and future episodes will affect the rapidity and distribution of aggradation; response and recovery planning will need to consider this, together with the impacts of climate changes on river flows.
This paper is the result of a study of the Ms = 7.8 Murchison earthquake which occurred in the South Island of New Zealand, on 16(UT) June 1929, a few years prior to the introduction of the first earthquake loadings code in New Zealand. It gives the first description of the damage to buildings in this event in modern earthquake engineering terms, and presents the first Modified Mercalli (MM) intensity map for the event determined from the original felt information. Some definitions of `well-built' pre-code buildings are proposed: these should help in dealing with safety and conservation issues raised when considering the future of such `earthquake risk' buildings. No evidence was found for MM10 intensities, although ground shaking of this strength probably occurred in the unpopulated mountainous countryside close to the fault rupture. Recommendations for improving the criteria for determining MM intensity are made in respect of (1) pre-code buildings and (2) seismically-induced landslides.
Seismic liquefaction occurred in northeast Kaiapoi during the 1901 Cheviot earthquake. A contemporary newspaper report describes the ejection of sand and lateral spreading in Waites' market garden at the east end of Sewell Street, Kaiapoi and also south of the Waimakariri River near Belfast. Piezocone probing and rotary drilling on the Waites property in Sewell Street and at three other sites in northeast Kaiapoi found loose, fine sands and silty sands with cone resistance 4: as low as 2 to 3 MPa; it is not surprising that liquefaction was observed in 1901. Lack of precise seismological parameters for the 1901 earthquake precludes any definite conclusions about the performance of liquefaction potential models. However, the occurrence of liquefaction strongly suggests that the M6.5 magnitude estimated by Dibble et al. [1980] is too small, and that local magnitude in 1901 was larger than the surface-wave value of about 6.9 of Dowrick and Smith [1990]. A value in the range of 7.1 to 7.5 seems more likely. Comparison of Dutch cone penetrometer resistances and standard penetration test N-values supports the old qc (bars)/N = 4 rule. Because of the large amount of scatter, use of the more refined rule of Robertson of Campanella, where qc /N is a function of D50, does not seem justified. The penetration testing results confirm that there is a significant risk of liquefaction at Kaiapoi. Furthermore, we now have four reference sites, each with slightly different soil conditions, whose performance can be monitored following future earthquakes in the region.
This is a general introduction to the four following articles by several authors who cooperated in making studies of various aspects of this major shock.
The instrumental epicenter of the Alaska earthquake of July 10, 1958, has been located on the hanging-wall side of the Fairweather fault near the surface expression of the fault and at the southeast end of the greatly disturbed area.
The fault-plane solution from P waves gives a fault plane which differs by 15° from the strike of the observed surface faulting. The theoretical relative amplitudes computed from the fault-plane solution are interpreted as partly explaining the residuals of P arrivals and inconsistent directions of the first motion of P.
The directions of polarization of the S waves are found to conform to the pattern expected for a single couple as the point-source model of the focal mechanism. A method is suggested for using S waves to check fault-plane solutions from P and to select the fault plane from the two nodal planes of P.
Observations of S at near stations do not correspond to the pattern expected for a couple. Large transverse motion is observed along the azimuth of the fault. In the western United States, at stations along the same azimuth, the SH motion changes progressively to SV with distance. Large SV components at distances of 25° to 27° indicate that the critical angle for SV may be reached at these distances and that even long S waves are refracted by structure within the crust.
