Active strike-slip faults and an outer frontal thrust in the Himalayan foreland basin

The Himalayan foreland basin formed by flexure of the Indian Plate below the advancing orogen. Motion on major thrusts within the orogen has resulted in damaging historical seismicity, whereas south of the Main Frontal Thrust (MFT), the foreland basin is typically portrayed as undeformed. Using two-...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2020-07, Vol.117 (30), p.17615-17621
Main Authors: Duvall, Michael J., Waldron, John W. F., Godin, Laurent, Najman, Yani
Format: Article
Language:English
Subjects:
Basins
Cenozoic
Deformation
Earthquake damage
Fault lines
Flexing
Geological faults
Geological time
Holocene
Mountains
Orogeny
Physical Sciences
Seismic surveys
Seismicity
Slip
Tectonics
Thrust
Trenching
Triangles
Unconformity
Wedges
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Summary:The Himalayan foreland basin formed by flexure of the Indian Plate below the advancing orogen. Motion on major thrusts within the orogen has resulted in damaging historical seismicity, whereas south of the Main Frontal Thrust (MFT), the foreland basin is typically portrayed as undeformed. Using two-dimensional seismic reflection data from eastern Nepal, we present evidence of recent deformation propagating >37 km south of the MFT. A system of tear faults at a high angle to the orogen is spatially localized above the Munger-Saharsa basement ridge. A blind thrust fault is interpreted in the subsurface, above the sub-Cenozoic unconformity, bounded by two tear faults. Deformation zones beneath the Bhadrapur topographic high record an incipient tectonic wedge or triangle zone. The faults record the subsurface propagation of the Main Himalayan Thrust (MHT) into the foreland basin as an outer frontal thrust, and provide a modern snapshot of the development of tectonic wedges and lateral discontinuities preserved in higher thrust sheets of the Himalaya, and in ancient orogens elsewhere. We estimate a cumulative slip of ~100 m, accumulated in
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2001979117