DOI: 10.1016/j.epsl.2018.04.045
Scopus记录号: 2-s2.0-85047094319
论文题名: Seismic imaging of the Main Frontal Thrust in Nepal reveals a shallow décollement and blind thrusting
作者: Almeida R.V. ; Hubbard J. ; Liberty L. ; Foster A. ; Sapkota S.N.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 494 起始页码: 216
结束页码: 225
语种: 英语
英文关键词: Himalayan earthquakes
; Main Frontal Thrust
; paleoseismology
; reflection seismic
; tectonic geomorphology
Scopus关键词: Fault slips
; Geomorphology
; Landforms
; Main Frontal Thrust
; Paleoseismic trenching
; Paleoseismology
; Quaternary sediments
; Recurrence intervals
; Reflection seismic
; Seismic reflection profiles
; Tectonic geomorphology
; Earthquakes
英文摘要: Because great earthquakes in the Himalaya have an average recurrence interval exceeding 500 yr, most of what we know about past earthquakes comes from paleoseismology and tectonic geomorphology studies of the youngest fault system there, the Main Frontal Thrust (MFT). However, these data are sparse relative to fault segmentation and length, and interpretations are often hard to validate in the absence of information about fault geometry. Here, we image the upper two km of strata in the vicinity of the fault tip of the MFT in central Nepal (around the town of Bardibas) applying a pre-stack migration approach to two new seismic reflection profiles that we interpret using quantitative fault-bend folding theory. Our results provide direct evidence that a shallow décollement produces both emergent (Patu thrust) and blind (Bardibas thrust) fault strands. We show that the décollement lies about 2 km below the land surface near the fault tip, and steps down to a regional 5 km deep décollement level to the north. This implies that there is significant variation in the depth of the décollement. We demonstrate that some active faults do not reach the surface, and therefore paleoseismic trenching alone cannot characterize the earthquake history at these locations. Although blind, these faults have associated growth strata that allow us to infer their most recent displacement history. We present the first direct evidence of fault dip on two fault strands of the MFT at depth that can allow terrace uplift measurements to be more accurately converted to fault slip. We identify a beveled erosional surface buried beneath Quaternary sediments, indicating that strath surface formation is modulated by both climate-related base level changes and tectonics. Together, these results indicate that subsurface imaging, in conjunction with traditional paleoseismological tools, can best characterize the history of fault slip in the Himalaya and other similar thrust fault systems. © 2018 The Author(s) Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109851
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Earth Observatory of Singapore, Nanyang Technological University, Singapore; Asian School of the Environment, Nanyang Technological University, Singapore; Department of Geosciences, Boise State UniversityID, United States; Département des sciences de la Terre et de l'atmosphère, Université du Québec à Montréal, Canada; Department of Mines and Geology, Kathmandu, 44600, Nepal
Recommended Citation:
Almeida R.V.,Hubbard J.,Liberty L.,et al. Seismic imaging of the Main Frontal Thrust in Nepal reveals a shallow décollement and blind thrusting[J]. Earth and Planetary Science Letters,2018-01-01,494