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Potential geomorphic consequences of a future Great (Mw 8.0+) Alpine Fault earthquake, South Island, New Zealand
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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... 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.
... The results have implications for both hazard mitigation strategies as well as understanding controls on channel morphology in steep, highly erosive environments. Furthermore, a deeper understanding of the potential downstream effects related to large scale landslide events and the related impacts on population centers may also improve our predictive abilities for the propagation of hazards by future landslide events (Dingle et al., 2017;Robinson and Davies, 2013), thereby reducing the losses associated with such catastrophic geomorphic events. Insights gained from observing landscape response to individual events provide important context for understanding how rare or extreme events influence landscape evolution. ...
... While the landslides themselves can be quite catastrophic (Tsou et al., 2011), the propagating impacts of the landslide material through the landscape can cause significant, long-lived hazards (Nguyen et al., 2013). For example, aggradation in downstream riverbeds following the event can change flood inundation patterns and frequency (Chen and Petley, 2005;Croissant et al., 2017a;Lane et al., 2007;Robinson and Davies, 2013;Stover and Montgomery, 2001) as well as influence channel bank mobility (Lane et al., 2007;Lisle, 1982). Regions with mountainous topography and high populations, such as Taiwan, are particularly vulnerable to cascading hazards associated with regional landsliding initiated by earthquakes and extreme precipitation. ...
Intense precipitation or seismic events can generate clustered mass movement processes across a landscape. These rare events have significant impacts on the landscape, however, the rarity of such events leads to uncertainty in how they impact the entire geomorphic system over a range of timescales. Taiwan is steep, tectonically active, and prone to landslide and debris flows, especially when exposed to heavy rainfall events. Typhoon Morakot made landfall in Taiwan in August of 2009, causing widespread landslides in southern Taiwan. The south to north trend in valley relief in southern Taiwan leads to spatial variability in landslide susceptibility providing an opportunity to infer the long-term impact of such landslide events on channel morphology. We use pre- and post-typhoon imagery to quantify the propagating impact of this event on channel width as the debris is routed through the landscape. The results show the importance of cascading hazards from landslides on landscape evolution based on patterns of channel width (both pre- and post-typhoon) and hillslope gradients in 20 basins along strike in southern Taiwan. Prior to Typhoon Morakot, the river channels in the central part of the study area were about 3–10 times wider than the channels in the south. Following the typhoon, aggradation and widening was also a maximum in these central to northern basins where hillslope gradients and channel steepness is high, accentuating the pre-typhoon pattern. The results further show that the narrowest channels are located where channel steepness is the lowest, an observation inconsistent with a detachment-limited model for river evolution. We infer this pattern is indicative of a strong role of sediment supply, and associated landslide events, on long-term channel evolution. These findings have implications across a range of spatial and temporal scales including understanding the cascade of hazards in steep landscapes and geomorphic interpretation of channel morphology.
... 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.
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.
The main objectives of this study are to assess the underlying causative factors for landslide occurrence due to earthquake in upper Indrawati Watershed of Nepal and evaluating the region prone to landslide using Landslide Susceptibility Mapping (LSM). We used logistic regression (LR) for LSM on geographic information system (GIS) platform. Nine causal factors (CF) including slope angle, aspect, elevation, curvature, distance to fault and river, geological formation, seismic intensity, and land cover were considered for LSM. We assessed the distribution of landslide among the classes of each CF to understand the relationship of CF and landslides. The northern part of the study area, which is dominated by steep rocky slope have a higher distribution of earthquake-induced landslides. Among the CF, 'slope' showed the positive correlation as landslide distribution is increasing with increasing slope. However, LR analysis depict 'distance to the fault' is the best predictor with the highest coefficient value. Susceptibility map was validated by assessing the correctly classified landslides under susceptibility categories, generated in five discrete classes using natural break (Jenk) methods. Calculation of area under curve (AUC) and seed cell area index (SCAI) were performed to validate the susceptibility map. The LSM approach shows good accuracy with respective AUC value for success rate and prediction rate of 0.795 and 0.702. Similarly, the decreasing SCAI value from very low to very high susceptibility categories advise satisfactory accuracy of LSM approach.
A c. AD 1620 West Coast earthquake has been attributed to the northern and central segments of the Alpine Fault but does not match well with paleoseismic indicators or the currently understood recurrence interval of Alpine Fault ruptures. We model the landsliding and resulting river aggradation from a Mw 7.6 earthquake on a modelled reverse fault located between the central Alpine Fault and the main divide of the Southern Alps. The Waiho–Callery and Whataroa catchments are significantly more impacted by coseismic landsliding from this Southern Alps earthquake than from an Alpine Fault earthquake. The modelling suggests that the c. AD 1620 earthquake was not an Alpine Fault event, and that large earthquakes on subsidiary faults (or fault systems) can have larger localised impacts on river behaviour west of the Southern Alps than an Alpine Fault earthquake.
Quaternary glaciations have repeatedly shaped large tracts of the Andean foreland. Its spectacular large glacial lakes, staircases of moraine ridges, and extensive outwash plains have inspired generations of scientists to reconstruct the processes, magnitude, and timing of ice build-up and decay at the mountain front. Surprisingly few of these studies noticed many dozens of giant (≥10⁸ m³) mass-wasting deposits in the foreland. We report some of the world's largest terrestrial landslides in the eastern piedmont of the Patagonian Ice Sheet (PIS) along the traces of the former Lago Buenos Aires and Lago Puyerredón glacier lobes and lakes. More than 283 large rotational slides and lateral spreads followed by debris slides, earthflows, rotational and translational rockslides, complex slides and few large rock avalanches detached some 164 ± 56 km³ of material from the slopes of volcanic mesetas, lake-bounding moraines, and river-gorge walls. Many of these landslide deposits intersect with well-dated moraine ridges or former glacial-lake shorelines, and offer opportunities for relative dating of slope failure. We estimate that >60% of the landslide volume (∼96 km³) detached after the Last Glacial Maximum (LGM). Giant slope failures cross-cutting shorelines of a large Late Glacial to Early Holocene lake (“glacial lake PIS”) likely occurred during successive lake-level drop between ∼11.5 and 8 ka, and some of them are the largest hitherto documented landslides in moraines. We conclude that 1) large portions of terminal moraines can fail catastrophically several thousand years after emplacement; 2) slopes formed by weak bedrock or unconsolidated glacial deposits bordering glacial lakes can release extremely large landslides; and 3) landslides still occur in the piedmont, particularly along postglacial gorges cut in response to falling lake levels.
The 2016 MW 7.8 Kaikōura earthquake involved complex rupture of multiple faults for > 170 km, generating strong ground shaking throughout the upper South Island leading to widespread landsliding. As a result of surface fault rupture and landslides, State Highway (SH) 1 and SH70 were blocked, isolating Kaikōura and the surrounding communities, and necessitating evacuations by air and sea. In all these respects, the Kaikōura earthquake can be considered an analogue for a future Alpine Fault earthquake, providing lessons for the necessary emergency response. Landslide blockages primarily occurred where surrounding slopes averaged > 17° and where peak ground acceleration was > 0.43 g, peak ground velocity was > 41 cm/s, or the modified Mercalli intensity was > 7.9. Using a potential future Alpine Fault scenario earthquake, this study identifies locations on other key state highway routes that have similar predictive variables that may, therefore, become blocked in a future earthquake. This suggests that SH6 between Hokitika and Haast, SH73 near Arthur’s Pass, and SH94 south of Milford Sound are all likely to be affected. This will necessitate the evacuation of large numbers of spatially distributed tourists as well as the resupply of isolated local populations. The possibility of bad weather along with a lack of sea ports south of Hokitika will likely make such activities challenging. Contingency planning based on experiences from the Kaikōura earthquake is therefore necessary and likely to prove invaluable following an Alpine Fault earthquake.
The Alpine Fault is the most major source of seismic hazard in the South Island of New Zealand, with the potential to produce a magnitude 8+ earthquake and associated ground shaking and co-seismic hazards (e.g. landslides and liquefaction), and severe, widespread and long-term impacts throughout southern and central New Zealand. Scientific investigation of the hazard and risk posed by the Alpine Fault to New Zealand society over recent decades, and several recent large earthquake disasters in New Zealand (the 2010-11 Canterbury earthquake sequence and the 2016 Kaikōura earthquake) have created considerable national, regional and local awareness and motivation to boost disaster risk management efforts for major earthquakes, further emphasizing the importance of Project AF8’s objectives. In July 2016, a project to develop a collective South Island emergency response plan was initiated, in partnership with all South Island CDEM groups and the Alpine Fault research community. This has become known as Project AF8 (Alpine Fault, magnitude 8). We describe the development and outcomes of the project, towards enhancing societal resilience to a future Alpine Fault earthquake.
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.
The M w 6.7 George Sound earthquake of October 15, 2007, occurred only a few kilometres offshore of Fiordland, within a region where the subduction zone of the Australian Plate beneath the Pacific Plate intersects the offshore extension of the Alpine Fault. Rapid response deployments of portable seismographs, a strong motion recorder and GPS receivers relatively close to the epicentre soon after the main shock allowed us to relate the event to thrusting at the subduction interface. The main shock moment tensor solution places the event at a shallow depth of 21 km. The sequence of aftershocks that followed the main event presents predominantly reverse faulting mechanisms with depths of 20 to 25 km. Earthquake re-locations using data recorded by the portable seismometers reveal a cluster of aftershocks at 17 to 25 km. This cluster defines a steeply SE-dipping plane, while another cluster at about 7-12 km depth images a NW-dipping plane within the overlying plate. Preliminary results from the seismic, geodetic and near-field strong motion geophysical data are consistent with rupture on an east dipping fault plane, presumed to be the subduction interface.
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.
