Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal)

The Charnath Khola is a large river crossing the Himalayan thrust system in the region devastated by the great M8.3 1934 Bihar-Nepal earthquake. Fluvial terraces are abandoned along the river and at the base of a ~20-m high cumulative thrust escarpment. A trench across the fault scarp exposed Siwali...

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Main Authors: Rizza, M., Bollinger, L., Sapkota, S. N., Tapponnier, P., Klinger, Y., Karakaş, C., Kali, E., Etchebes, M., Tiwari, D. R., Siwakoti, I., Bitri, A., Bes de Berc, S.
Other Authors: Asian School of the Environment
Format: Article
Language:English
Published: 2020
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Online Access:https://hdl.handle.net/10356/143321
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1433212020-09-26T21:30:58Z Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal) Rizza, M. Bollinger, L. Sapkota, S. N. Tapponnier, P. Klinger, Y. Karakaş, C. Kali, E. Etchebes, M. Tiwari, D. R. Siwakoti, I. Bitri, A. Bes de Berc, S. Asian School of the Environment Earth Observatory of Singapore Science::General Earthquake Surface Rupture The Charnath Khola is a large river crossing the Himalayan thrust system in the region devastated by the great M8.3 1934 Bihar-Nepal earthquake. Fluvial terraces are abandoned along the river and at the base of a ~20-m high cumulative thrust escarpment. A trench across the fault scarp exposed Siwalik mudstone/siltstone overthrusting Quaternary units and three colluvial wedges interfingered with fluvial sands. The 85 accelerator mass spectrometry radiocarbon dates, from detrital charcoals sampled in the trench, a river cut and river terraces, constrain the timing of the sedimentary processes following the last two major earthquakes, in 1934 and 1255 CE. Although several samples straddle the main earthquake horizon, associating it with the 1934 earthquake, based solely on radiocarbon ages, remains challenging. The 49 detrital charcoal ages found in the pre-earthquake and postearthquake units fall between 65 and 225 BP, a period with a flat calibration curve. Many of these radiocarbon ages are suspected to include a part due to inbuilt time (i.e., age of the wood at the time of burning), transport time, and reworking processes, which are difficult to resolve. Considering these ages at their face value could lead to dates older than the actual earthquake dates. We suggest that a part of this chronological bias is also related to a local postseismic aggradation pulse of 4 to 5 m of sediments, which is documented in the trench and terraces. This fluvial sequence, hiding the most recent surface rupture, is likely related to landslide-sediment deposition triggered by the 1934 Bihar-Nepal earthquake. Ministry of Education (MOE) National Research Foundation (NRF) Published version 2020-08-24T01:59:03Z 2020-08-24T01:59:03Z 2019 Journal Article Rizza, M., Bollinger, L., Sapkota, S. N., Tapponnier, P., Klinger, Y., Karakaş, Ç., ... Bes de Berc, S. (2019). Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar‐Nepal earthquake ruptures at Charnath Khola (eastern Nepal). Journal of Geophysical Research: Solid Earth, 124(8), 9182-9207. doi:10.1029/2018jb016376 2169-9313 https://hdl.handle.net/10356/143321 10.1029/2018JB016376 2-s2.0-85070752173 8 124 9182 9207 en Journal of Geophysical Research: Solid Earth © 2019 American Geophysical Union. All rights reserved. This paper was published in Journal of Geophysical Research: Solid Earth and is made available with permission of American Geophysical Union. application/pdf
institution Nanyang Technological University
building NTU Library
country Singapore
collection DR-NTU
language English
topic Science::General
Earthquake
Surface Rupture
spellingShingle Science::General
Earthquake
Surface Rupture
Rizza, M.
Bollinger, L.
Sapkota, S. N.
Tapponnier, P.
Klinger, Y.
Karakaş, C.
Kali, E.
Etchebes, M.
Tiwari, D. R.
Siwakoti, I.
Bitri, A.
Bes de Berc, S.
Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal)
description The Charnath Khola is a large river crossing the Himalayan thrust system in the region devastated by the great M8.3 1934 Bihar-Nepal earthquake. Fluvial terraces are abandoned along the river and at the base of a ~20-m high cumulative thrust escarpment. A trench across the fault scarp exposed Siwalik mudstone/siltstone overthrusting Quaternary units and three colluvial wedges interfingered with fluvial sands. The 85 accelerator mass spectrometry radiocarbon dates, from detrital charcoals sampled in the trench, a river cut and river terraces, constrain the timing of the sedimentary processes following the last two major earthquakes, in 1934 and 1255 CE. Although several samples straddle the main earthquake horizon, associating it with the 1934 earthquake, based solely on radiocarbon ages, remains challenging. The 49 detrital charcoal ages found in the pre-earthquake and postearthquake units fall between 65 and 225 BP, a period with a flat calibration curve. Many of these radiocarbon ages are suspected to include a part due to inbuilt time (i.e., age of the wood at the time of burning), transport time, and reworking processes, which are difficult to resolve. Considering these ages at their face value could lead to dates older than the actual earthquake dates. We suggest that a part of this chronological bias is also related to a local postseismic aggradation pulse of 4 to 5 m of sediments, which is documented in the trench and terraces. This fluvial sequence, hiding the most recent surface rupture, is likely related to landslide-sediment deposition triggered by the 1934 Bihar-Nepal earthquake.
author2 Asian School of the Environment
author_facet Asian School of the Environment
Rizza, M.
Bollinger, L.
Sapkota, S. N.
Tapponnier, P.
Klinger, Y.
Karakaş, C.
Kali, E.
Etchebes, M.
Tiwari, D. R.
Siwakoti, I.
Bitri, A.
Bes de Berc, S.
format Article
author Rizza, M.
Bollinger, L.
Sapkota, S. N.
Tapponnier, P.
Klinger, Y.
Karakaş, C.
Kali, E.
Etchebes, M.
Tiwari, D. R.
Siwakoti, I.
Bitri, A.
Bes de Berc, S.
author_sort Rizza, M.
title Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal)
title_short Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal)
title_full Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal)
title_fullStr Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal)
title_full_unstemmed Post earthquake aggradation processes to hide surface ruptures in thrust systems : the M8.3, 1934, Bihar-Nepal earthquake ruptures at Charnath Khola (eastern Nepal)
title_sort post earthquake aggradation processes to hide surface ruptures in thrust systems : the m8.3, 1934, bihar-nepal earthquake ruptures at charnath khola (eastern nepal)
publishDate 2020
url https://hdl.handle.net/10356/143321
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