Influence Of Lithospheric Scale Basement Faults On Seismicity In The Himalayan Orogenic System

Abstract

The Himalayan system is the result of a continental collision that occurred approximately 55 million years ago between the Indian and Asian tectonic plates1,2. The collision resulted in the underthrust of the Indian crust beneath Asia, and a deformed crustal wedge3,4. The Indian plate records a complex pre-Himalayan geological history that includes several basement faults that reach depths of 70 kilometres and are oriented at a high angle to the Himalayan front5. These basement faults bound topographic basement highs that are interpreted to limit the rupture of Himalayan earthquakes6. Recent research suggests the basement faults control the distribution and magnitude of seismicity along the Himalaya7. 
 The Himalayan system serves as a prototype for novel three-dimensional numerical modelling to understand if and how inherited basement structures influence seismicity in orogenic settings. Models are generated using the Coreform Cubit meshing software and are run on the supercomputer platform hosted at the University of Toronto. The initial model contains three crustal blocks: the Indian crust, a deformed orogenic wedge, and the Asian crust, all cut at a high angle by a lithospheric scale basement fault. The 2015 7.9 MW Gorkha earthquake is simulated, and slip is generated along the Himalayan basal detachment. Seismograms, shear wave potential, and compressional wave potential movies are created to understand if and how the inherited basement faults influence seismicity within orogenic systems. Understanding how these regionally significant basement faults influence seismicity in the densely populated regions of northern India and Nepal is of utmost societal importance. 
 References 
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