Seismic and aseismic fault growth lead to different fault orientations

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1029/2019JB017324.

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Authors

Simon Preuss , Robert Herrendörfer, Taras Gerya, Jean-Paul Ampuero , Ylona van Dinther 

Abstract

Orientations of natural fault systems are subject to large variations. They often contradict classical Andersonian faulting theory as they are misoriented relative to the prevailing regional stress field. This is ascribed to local effects of structural or stress heterogeneities and reorientations of structures or stresses on the long-term. To better understand the relation between fault orientation and regional stresses, we simulate spontaneous fault growth and its effect on the stress field. Our approach incorporates earthquake rupture dynamics, visco-elasto-plastic brittle deformation and a rate-and state- dependent friction formulation in a continuum mechanics framework. We investigate how strike slip faults orient according to local and far-field stresses during their growth. We identify two modes of fault growth, seismic and aseismic, distinguished by different fault angles and slip velocities. Seismic fault growth causes a significant elevation of dynamic stresses and friction values ahead of the propagating fault tip. These elevated quantities result in a greater strike angle relative to the maximum principal regional stress than that of a fault segment formed aseismically. When compared to the near-tip time-dependent stress field the fault orientations produced by both growth modes follow Anderson’s classical faulting theory. We demonstrate how the two types of fault growth may be distinguished in natural faults by comparing their angles relative to the original regional max- imum principal stress. A stress field analysis of the Landers-Mojave fault suggests that
an angle greater than approximately 25° between two faults indicates seismic fault growth.

DOI

https://doi.org/10.31223/osf.io/an92e

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Keywords

numerical modeling, , Fault growth, Andersonian and Coulomb faulting, Continuum mechanics, Earthquake rupture dynamics, Fault angle, Rate-and state-dependent friction, Stress field

Dates

Published: 2019-01-10 04:01

Last Updated: 2019-01-17 06:43

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License

CC BY Attribution 4.0 International

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