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The fate of sediment after a large earthquake

Francis, Oliver, Fan, Xuanmei, Hales, Tristram ORCID:, Hobley, Daniel ORCID:, Xu, Qiang and Huang, Runqiu 2022. The fate of sediment after a large earthquake. Journal of Geophysical Research. Earth Surface 127 (3) , e2021JF006352. 10.1029/2021JF006352

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Large earthquakes rapidly denude hillslopes by triggering thousands of coseismic landslides. The sediment produced by these landslides is initially quickly mobilised from the landscape by an interconnected cascade of processes. This cascade can dramatically but briefly enhance local erosion rates. Hillslope and channel processes, such as landsliding and debris flows, interact to influence the total mass, caliber, and rate of sediment transport through catchments. Calculating the sediment budget of an earthquake lends insight into the nature of these interactions. Using satellite imagery derived landslide inventories, channel surveys and a literature review combined with a Monte Carlo simulation approach we present a constrained sediment budget of the first decade after the 2008 Mw7.9 Wenchuan earthquake. With this sediment budget we demonstrate that debris flows are dominant process for delivering sediment into channels and that large volumes of sediment remain in the landscape. In our study area over 88% (469.7 Mega tonnes) of the coseismically generated sediment remains on the hillslopes in 2018. Of the 12% of the sediment that was mobilised, 67% (45.2 ± 22 Mt) was mobilised by debris flows. Despite the large proportion of sediment remaining on the hillslope, the frequency of debris flows declined significantly over our observation period. The reduction in debris-flow frequency is not correlated to reductions in the frequency of triggering storms, suggesting changes in the mechanical properties of hillslope sediment may drive this observation. The stabilization of coseismically generated sediment greatly extends its residence time and may influence catchment sediment yields for centuries or millennia.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Environmental Sciences
Additional Information: This is an open access article under the terms of the Creative Commons Attribution License
Publisher: John Wiley and Sons Inc.
ISSN: 2169-9003
Funders: NERC, ESRC
Date of First Compliant Deposit: 28 February 2022
Date of Acceptance: 20 February 2022
Last Modified: 17 May 2023 21:25

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