Late Quaternary Seismicity and Climate in the Western Nepal : Himalaya

• Main Author: Ghazoui, Zakaria
• Other Authors: Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement IRD : UR219-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Rijksuniversiteit te Gent. Sectie Mariene Biologie, Peter van der Beek, Sébastien Bertrand
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2018
• Subjects: Glacier; Sediment; Seismology; Paleoseismology; Climate; Quaternary; Paleosismologie; Climat; Quaternaire; Sismologie; Sédiment; [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Indian; Ice cap
• Online Access: https://tel.archives-ouvertes.fr/tel-01935412; https://tel.archives-ouvertes.fr/tel-01935412/document; https://tel.archives-ouvertes.fr/tel-01935412/file/GHAZOUI_2018_archivage.pdf

The Himalayan collision, in which India underthrusts below Tibet, regularly produces major destructive earthquakes in Nepal and its neighboring countries, most of which are fatal to nearby communities. As a wall dividing the Indian plains and the Tibetan plateau, the Himalaya also significantly modifies the atmospheric circulation, affecting both the local and global climate. This thesis explores the poorly known Quaternary history and evolution of Himalayan climate and seismicity, more particularly in the least populated and most remote region of Western Nepal. In terms of climate and environmental change, one of the least understood aspects of Himalayan history during the late Quaternary is the extension of glaciers and their impacts on landscape evolution. Based on field observations, cosmogenic nuclide dating (10Be) and satellite observations, we estimated the maximum extent of glaciers during the Last Glacial Maximum, which supports the hypothesis of a relatively large glacier cover, but not of an extended ice cap, at the scale of Western Nepal. In terms of seismology, the social, economic and political implications of the occurrence of an earthquake of higher magnitude than the recent earthquake of 2015, whose epicenter is located near the city of Gorkha, is a major concern and largely motivates this thesis. The last major earthquake of magnitude greater than 8 (Mb) took place on 6 June 1505 and had a profound impact on the Nepalese population and the surrounding area. In Western Nepal the 1505 event was the last earthquake that ruptured the Main Frontal Thrust according to historical archives and paleoseismological studies, which gave rise to the concept of a seismic gap in western Nepal and adjacent areas in northern India. With this in mind, this thesis addresses two major issues on the Himalayan seismic behavior: on the first hand is the hypothesis of a seismic gap in the central Himalaya and on the second the temporal distribution of earthquakes during the late Quaternary. For this purpose, a new ...