On a flawed conclusion that the 1255 A.D. earthquake ruptured 800 km of the Himalayan Frontal Thrust east of Kathmandu

Pierce, Ian; Wesnousky, Steven G.

doi:10.1002/2016gl070426

Cited by 16 publications

(7 citation statements)

References 6 publications

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“…An extreme example of enthusiastically connecting weakly constrained dates from palaeoseismic trenches is the suggestion by Mishra et al (2016) that the 7 June 1255 earthquake, for which we have a single-line historical account from the Kathmandu Valley (Pant 2002), ruptured 800 km eastwards from 86°E to 94°E. Pierce & Wesnousky (2016) demonstrated that data from six of the seven trench sites invoked in this extrapolation use data with large uncertainties, and that their association with a 1255 rupture is unjustifiable and misleading. The timing of a palaeoseismic earthquake is bracketed by the age of ruptured sediments and by the age of undisturbed sedimentary cover, which provide minimum and maximum bounds for the time of the causal earthquake.…”

Section: Palaeoseismic Studies Of Great Earthquakesmentioning

confidence: 95%

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Bilham

2019

249

198

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This article summarizes recent advances in our knowledge of the past 1000 years of earthquakes in the Himalaya using geodetic, historical and seismological data, and identifies segments of the Himalaya that remain unruptured. The width of the Main Himalayan Thrust is quantified along the arc, together with estimates for the bounding coordinates of historical rupture zones, convergence rates, rupture propagation directions as constrained by felt intensities. The 2018 slip potential for fifteen segments of the Himalaya are evaluated and potential magnitudes assessed for future earthquakes should these segments fail in isolation or as contiguous ruptures. Ten of these fifteen segments are sufficiently mature currently to host a great earthquake (M w ≥ 8). Fatal Himalayan earthquakes have in the past occurred mostly in the daylight hours. The death toll from a future nocturnal earthquake in the Himalaya could possibly exceed 100 000 due to increased populations and the vulnerability of present-day construction methods. Himalayan geodesy The rate of convergence of India relative to EuroAsia is fundamental to quantifying the anticipated

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Section: Palaeoseismic Studies Of Great Earthquakesmentioning

confidence: 95%

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Bilham

2019

249

198

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“…4). Although two or three great medieval earthquakes were inferred from paleoseismic trenches in Nepal, of which the historic 1255 earthquake has attracted the most attention, their exact magnitude and extent of slip remain controversial 8,14–16 . Surface ruptures attributed to the 1255 earthquake have recently been documented from locations to the south and southwest of Kathmandu 36 .…”

Section: Resultsmentioning

confidence: 99%

Potentially large post-1505 AD earthquakes in western Nepal revealed by a lake sediment record

et al. 2019

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According to paleoseismological studies, the last earthquake that ruptured the Main Frontal Thrust in western Nepal occurred in 1505 AD. No evidence of large earthquakes has been documented since, giving rise to the concept of a seismic gap in the central Himalaya. Here, we report on a new record of earthquake-triggered turbidites from Lake Rara, western Nepal. Our lake-sediment record contains eight possibly moderate-to-large earthquake-triggered turbidites during the last 800 years, three of which overlap in age with previously reported M w ≥ 7 events in western Nepal. Shaking intensity modelling, together with instrumental records, suggests that near-field earthquakes (≤15 km) should have a minimum M w 5.6, and regional earthquakes (≤80 km) a M w > ~ 6.5, to trigger turbidites. We present a likely scenario that western Nepal may be as seismically active as central Nepal; however, more data are needed to revaluate the seismic risk in the central Himalaya.

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“…In the Kathmandu area, the 1255 earthquake is a major event (Pant, 2002), although his location is presently strongly debated (Pierce et al, 2016). By taking into account the synthesis performed by Mugnier et al (2013) and the recent trenches performed by Chamlagain et al (2016), we consider that this earthquake ruptured the MHT both south and west of Kathmandu.…”

Section: Towards a "Barrier Type" Framework For Interpreting The Succession Of Historic Earthquakes In Central Himalayamentioning

confidence: 93%

Segmentation of the Himalayan megathrust around the Gorkha earthquake (25 April 2015) in Nepal

Mugnier

Jouanne

Bhattarai

et al. 2017

Journal of Asian Earth Sciences

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We put the 25 April 2015 earthquake of Nepal (Mw 7.9) into its structural geological context in order to specify the role of the segmentation of the Himalayan megathrust. The rupture is mainly located NW of Kathmandu, at a depth of 13-15 km on a flat portion of the Main Himalayan Thrust (MHT) that dips towards the N-NE by 7 to 10°. The northern bound of the main rupture corresponds to the transition towards a steeper crustal ramp. This ramp, which is partly coupled during the interseismic period, is only locally affected by the earthquake. The southern bound of the rupture was near the leading edge of the Lesser Himalaya antiformal duplex and near the frontal footwall ramp of the upper Nawakot duplex. The rupture has been affected by transversal structures: on the western side, the Judi lineament separates the main rupture zone from the nucleation area; on the eastern side, the Gaurishankar lineament separates the 25 April 2015 rupture from the 12 May 2015 (Mw 7.2) rupture. The origin of these lineaments is very complex: they are probably linked to pre-Himalayan faults that extend into the Indian shield beneath the MHT. These inherited faults induce transverse warping of the upper lithosphere beneath the MHT, control the location of lateral ramps of the thrust system and concentrate the hanging wall deformation at the lateral edge of the ruptures.The MHT is therefore segmented by stable barriers that define at least five patches in Central Nepal. These barriers influence the extent of the earthquake ruptures. For the last two centuries: the 1833 (Mw 7.6) earthquake was rather similar in extent to the 2015 event but its rupture propagated south-westwards from an epicentre located NE of Kathmandu; the patch south of Kathmandu was probably affected by at least three earthquakes of Mw ≥ 7 that followed the 1833 event a few days later or 33 years (1866 event, Mw 7.2) later; the 1934 *Manuscript Click here to download Manuscript: Himalaya-Mugnier-JAES_final.docx Click here to view linked References earthquake (Mw 8.4) had an epicentre ~170 km east of Kathmandu, may have propagated as far as Kathmandu and jumped the Gaurishankar lineament.This combined structural approach and earthquake study allows us to propose that the MHT in the central/eastern Himalaya is segmented by stable barriers that define barrier-type earthquake families. However for each individual earthquake within a family, the rupture histories could be different. Furthermore, the greatest earthquakes could have broken the barriers and affected the patches of several families. The concept of a regular recurrence of characteristic earthquakes is therefore misleading to describe the succession of Himalayan earthquakes.

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On a flawed conclusion that the 1255 A.D. earthquake ruptured 800 km of the Himalayan Frontal Thrust east of Kathmandu

Cited by 16 publications

References 6 publications

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Potentially large post-1505 AD earthquakes in western Nepal revealed by a lake sediment record

Segmentation of the Himalayan megathrust around the Gorkha earthquake (25 April 2015) in Nepal

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