Topographic modulation of fault kinematics in the Himalaya and Tibet

This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint.

Add a Comment

You must log in to post a comment.


Comments

There are no comments or no comments have been made public for this article.

Downloads

Download Preprint

Supplementary Files
Authors

Richard Styron

Abstract

In many locations in the Himalaya and Tibet, extensional stepovers on strike-slip faults occur beneath pre-existing topographic highs. An influential physical model of orogens, explaining contemporaneous high-elevation normal faulting and low-elevation reverse faulting, holds that horizontal tectonic compression is invariant across the orogen while vertical stress varies with topography, changing the balance of stresses. This model is two-dimensional and requires topography to be supported isostatically, and therefore cannot fully describe strike-slip to normal fault transitions beneath mountains to small mountain ranges, as this is a three-dimensional deformation field and topography of this wavelength is supported isostatically. I introduce a 3D elastic model describing the modulation of fault kinematics by shorter-wavelength topographic stress, and show how the model can place constraints on the tectonic stress field. I then calculate the topographic stress field on the Western Nepal Fault System, and use topographic stresses and observed fault kinematics to invert for the tectonic stress field. The results yield a maximum tectonic compression of 0–0.2 rho gz and minimum tectonic compression of -0.1–0.1 rho gz, and reproduce kinematics from normal, strike-slip and thrust faults and earthquakes in and around western Nepal, including the 2015 Gorkha earthquake. This demonstrates that where vertical and a horizontal principal stress are near equal, 1-10 km scale variations in topography can change fault kinematics, and that pre-existing topography can influence the location of subsequent faults and stepovers.

DOI

https://doi.org/10.31223/osf.io/8z9ha

Subjects

Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure

Keywords

Stress, faulting, Tectonics, Tibet, Earthquakes, Nepal, bayes, topographic stress

Dates

Published: 2017-12-21 17:17

License

CC BY Attribution 4.0 International