How Far South Might Himalayan Earthquakes Occur?

A recent article published in the Proceedings of the National Academy of Sciences that explores the Himalayan foreland basin and the faults buried underneath it. Although the faults are thought to slip only once every thousand years, this research helps us to better understand the seismic risk in this densely populated area. Article Title: Active strike-slip faults and an outer frontal thrust in the Himalayan foreland basin Authors: Michael J. Duvall, John W.F. Waldron, Laurent Godin, and Yani Najman Abstract from paper: "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 more than 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 less than 0.5 Ma, over a minimum slipped area of ∼780 km2. These observations demonstrate that Himalayan ruptures may pass under the present-day trace of the MFT as blind faults inaccessible to trenching, and that paleoseismic studies may underestimate Holocene convergence."

______________________________

Special Thanks

The Natural Sciences and Engineering Research Council of Canada for the funding through their Discovery Grants John Clayburn and Cairn Energy for their contributions to the project Schlumberger for donating the Petrel software license to the University of Alberta. The software assisted with data analysis in this project. All of our field guides as well as Alison Martin for her field work assistance

_______________________________

Credits

Footage of Nepal Earthquake - Amateur video via BBC News Nepal earthquake photo courtesty SIM Central and South East Asia via Flickr Music - "Divine Life Society" by Jesse Gallagher Ancient Earth Globe animation - Paleogeographic maps by C.R. Scotese, visualizations developed by Ian Webster _________________________________

Video created by The University of Texas' Geoscience Studio