Papers on Geodesy and Gravity Tectonophysics
Modeling mountain building and the seismic cycle in the Himalaya of Nepal
Article first published online: 20 SEP 2012
Copyright 2000 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 105, Issue B6, pages 13389–13407, 10 June 2000
How to Cite
2000), Modeling mountain building and the seismic cycle in the Himalaya of Nepal, J. Geophys. Res., 105(B6), 13389–13407, doi:10.1029/2000JB900032., and (
- Issue published online: 20 SEP 2012
- Article first published online: 20 SEP 2012
- Manuscript Accepted: 28 JAN 2000
- Manuscript Received: 21 APR 1999
A host of information is now available regarding the geological and thermal structure as well as deformation rate across the Himalaya of central Nepal. These data are reconciled in a two-dimensional mechanical model that incorporates the rheological layering of the crust which depends on the local temperature and surface processes. Over geological timescale (5 Ma) the ∼20 mm/yr estimated shortening rate across the range is accommodated by localized thrust faulting along the Main Himalayan Thrust fault (MHT). The MHT reaches the surface along the foothills, where it is called the Main Frontal Thrust fault (MFT). The MHT flattens beneath the Lesser Himalaya and forms a midcrustal ramp at the front of the Higher Himalaya, consistent with the river incision and the anticlinal structure of the Lesser Himalaya. Farther northward the MHT roots into a subhorizontal shear zone that coincides with a midcrustal seismic reflector. Aseismic slip along this shear zone is accommodated in the interseismic period by elastic straining of the upper crust, increasing the Coulomb stress beneath the front of the Higher Himalaya, where most of the microseismic activity clusters. Negligible deformation of the hanging wall requires a low apparent friction coefficient (μ) less than ∼0.3 on the flat portion of the MHT. On the ramp, μ might be as high as 0.6. Sensitivity tests show that a rather compliant, quartz-rich rheology and a high radioactive heat production in the upper crust of ∼2.5 μW/m3 is required. Erosion affects the thermal structure and interplays with crustal deformation. A dynamic equilibrium is obtained in which erosion balances tectonic uplift maintaining steady state thermal structure, topography, and deformation field. Using a linear diffusion model of erosion, we constrain the value of the mass diffusivity coefficient to 0.5–1.6×l04 m2/yr. This study demonstrates that the data are internally consistent and compatible with current understanding of the mechanics of crustal deformation and highlight the role of viscous flow in the lower crust and of surface erosion in orogeny processes on the long term as well as during interseismic period.