Microscale stress heterogeneities: Mechanical, rheological, and mineralogical impact

by Scott E. Johnson, Christopher Gerbi, Won Joon Song and He Feng

The roots of lithospheric rheology lie at the grain scale, where mineral assemblages and microstructure respond to their environment. Phase shapes, distributions, and orientations transform macroscale loading into microscale stress and strain(-rate) fields, which in turn feed back to the macroscale response. Because of the heterogeneity induced by the inherent anisotropy of rock microstructure, these microscale fields can vary significantly from the bulk conditions. We present some examples of how microscale stresses influence microstructural evolution and rock rheology. 

Cite as:

Johnson, S. E., Gerbi, C., Song, W. J., & Feng, H.. (2020, July 20). Microscale stress heterogeneities: Mechanical, rheological, and mineralogical impact (Version 1). Tectonics Community Science Workshop 2020.

author = "Scott E. Johnson, Christopher Gerbi, Won Joon Song and  He Feng",
title = "{Microscale stress heterogeneities: Mechanical, rheological, and mineralogical impact (Version 1)}",
year = "2020",
month = "7",
url = "",
doi = 10.6084/m9.figshare.12674519.v1}



Posted by Pamela Burnley on Jul 28th, 2020

I really like your poster, it’s very interesting! In panel 2, for the simulations, I assume that the grey lines are grain boundaries. What are the black lines in the center? Also how do you simulate microcracking in TESA? You show a plot of stress vs steps in the simulation, what is changing for each step? I see that the stress spikes a lot, but if this is an elastic simulation what allows the stress to decay? Is PLC also included in the simulation? Sorry for asking a lot of questions, it looks like your modeling technique would be useful to me in several different areas, so I want to make sure I really understand it.

PS – as you can see from my poster I completely agree with you about the importance of local/grain scale fluctuations in stress and strain.


Posted by Chris Gerbi on Jul 29th, 2020

Thanks for the queries. Yes, gray lines are grain boundaries; black lines are fractures. The failure happens when sigma1 exceeds 50MPa in these simulations. Scott explored shear failure also, and found that it wasn't as significant (surprising to me). In the stress v. steps, the plots are the maximum sigma1 across the model; the change with each step is due to stress readjustment following fracture incremental propagation. This work is all elastic + failure; no viscous component here.



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