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Geomorphology reveals active decollement geometry in the central Himalayan seismic gap

Morell, Kristin D and Sandiford, Mike and Rajendran, CP and Rajendran, Kusala and Alimanovic, Abaz and Fink, David and Sanwal, Jaishri (2015) Geomorphology reveals active decollement geometry in the central Himalayan seismic gap. In: LITHOSPHERE, 7 (3). pp. 247-256.

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Official URL: http://dx.doi.org/10.1130/L407.1


The similar to 700-km-long ``central seismic gap'' is the most prominent segment of the Himalayan front not to have ruptured in a major earthquake during the last 200-500 yr. This prolonged seismic quiescence has led to the proposition that this region, with a population >10 million, is overdue for a great earthquake. Despite the region's recognized seismic risk, the geometry of faults likely to host large earthquakes remains poorly understood. Here, we place new constraints on the spatial distribution of rock uplift within the western similar to 400 km of the central seismic gap using topographic and river profile analyses together with basinwide erosion rate estimates from cosmogenic Be-10. The data sets show a distinctive physiographic transition at the base of the high Himalaya in the state of Uttarakhand, India, characterized by abrupt strike-normal increases in channel steepness and a tenfold increase in erosion rates. When combined with previously published geophysical imaging and seismicity data sets, we interpret the observed spatial distribution of erosion rates and channel steepness to reflect the landscape response to spatially variable rock uplift due to a structurally coherent ramp-flat system of the Main Himalayan Thrust. Although it remains unresolved whether the kinematics of the Main Himalayan Thrust ramp involve an emergent fault or duplex, the landscape and erosion rate patterns suggest that the decollement beneath the state of Uttarakhand provides a sufficiently large and coherent fault segment capable of hosting a great earthquake.

Item Type: Journal Article
Publication: LITHOSPHERE
Additional Information: Copy right for this article belongs to the GEOLOGICAL SOC AMER, INC, PO BOX 9140, BOULDER, CO 80301-9140 USA
Department/Centre: Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited: 05 Aug 2015 06:18
Last Modified: 05 Aug 2015 06:18
URI: http://eprints.iisc.ac.in/id/eprint/52034

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