Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya

Schwanghart, Wolfgang; Bernhardt, Anne; Stolle, Amelie; Hoelzmann, Philipp; Adhikari, Basanta Raj; Andermann, Christoff; Tofelde, Stefanie; Merchel, Silke; Rugel, G.; Fort, Monique; Korup, Oliver

doi:10.1126/science.aac9865

Cited by 74 publications

(81 citation statements)

References 45 publications

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“…The magnitude of observed channel change due to aggradation is quite significant in some of the basins, such as West 1 (Figure ). Paleo‐landslide events responsible for terrace formation have been documented in previous studies, although those studies attribute the terraces to seismically induced landslides (McPhillips et al ., ; Schwanghart et al ., ). An implication of our observations is that individual, large magnitude atmospheric events, such as tropical cyclones, may be capable of generating lasting terraces due to the cascade of geomorphic processes associated with regional landsliding.…”

Section: Discussionmentioning

confidence: 97%

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Yanites

Mitchell

Bregy

et al. 2018

Earth Surf Processes Landf

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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. Copyright © 2018 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 97%

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Yanites

Mitchell

Bregy

et al. 2018

Earth Surf Processes Landf

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“…1 These inventories show landslides of relatively small size and few river dams, compared with other recent earthquaketriggered landslides of similar magnitude in Pakistan (Owen et al 2008) or in China (Gorum et al 2011), or after medieval earthquakes in the same area (Schwanghart et al 2015). Reasons for this small number of landslides are still in debate.…”

Section: Introductionmentioning

confidence: 94%

Landslides triggered by the Gorkha earthquake in the Langtang valley, volumes and initiation processes

Lacroix

2016

Earth Planets Space

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The Gorkha earthquake (Nepal, 2015, M w 7.9) triggered many landslides. The most catastrophic mass movement was a debris avalanche that buried several villages in the Langtang valley. In this study, questions are raised about its volume and initiation. I investigate the possibility of high-resolution digital surface models computed from tri-stereo SPOT6/7 images to resolve this issue. This high-resolution dataset enables me to derive an inventory of 160 landslides triggered by this earthquake. I analyze the source of errors and estimate the uncertainties in the landslide volumes. The vegetation prevents to correctly estimate the volumes of landslides that occured in vegetated areas. However, I evaluate the volume and thickness of 73 landslides developing in vegetated-free areas, showing a power law between their surface areas and volumes with exponent of 1.20. Accumulations and depletion volumes are also well constrained for larger landslides, and I find that the main debris avalanches accumulated 6.95 × 10 6 m 3 of deposits in the valley with thicknesses reaching 60 m, and 9.66 × 10 6 m 3 in the glaciated part above 5000 m asl. The large amount of sediments is explained by an initiation of the debris avalanche due to serac falls and snow avalanches from five separate places between 6800 and 7200 m asl over 3 km length.

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“…are highest for the Sir Khola scarp and gradually decrease toward the east with the lowest values for the Harmutty scarp (Figure ). This implies that the Marha Khola scarp could not be ascribed to the 1255 event; hence, we believe that it may be of a separate event either related to A.D. 1100 or 1223 [ Lavé et al ., ; Schwanghart et al ., ].…”

Section: Status Of Giant Surface‐rupturing Events In Eastern Himalayamentioning

confidence: 99%

Paleoseismic evidence of a giant medieval earthquake in the eastern Himalaya

Mishra

Singh

Pandey

et al. 2016

Geophysical Research Letters

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We present here the results of a paleoseismic investigation carried across a ~10 m high fault scarp at Panijhora village, West Bengal in northeastern India. Accelerator Mass Spectrometer analyzed 14C radiocarbon age constraints from six detrital charcoal samples ranging between 1688 B.C. and A.D. 1152 are consistent with the great medieval earthquake of A.D. 1255 that is interpreted to have produced a minimum observed fault slip of ~5 m in the trench exposure. Recalibration of radiocarbon ages from previous studies at Harmutty, Nameri, and Marha in the eastern Himalaya using Bayesian statistical analyses further substantiates the possibility that the A.D. 1255 earthquake might have ruptured the Himalayan front over a length of ~800 km from ~85.87° to 93.76°E longitudes.

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Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya

Cited by 74 publications

References 45 publications

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Landslides triggered by the Gorkha earthquake in the Langtang valley, volumes and initiation processes

Paleoseismic evidence of a giant medieval earthquake in the eastern Himalaya

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