[CIG-SHORT] Normal Force and shear force on an inclined plane

[Qian Gao]

Hi, Brad,

Thank you very much for your suggestions !

I searched some papers about faulting, yes, you are right, most people use
stress state to evaluate the stability of an fault, rather than force.

I find you replied most of questions in mailing list. A lot of people, I
think, would like to shear your work, however, you have a better
understanding of Pylith or the knowledge about earthquake.

Thanks again!

Best Regards!
Qian Gao



On Mon, Oct 24, 2011 at 12:02 PM, Brad Aagaard <baagaard at usgs.gov> wrote:

> Qian,
>
> In PyLith the shear and normal tractions on a fault are available via the
> output. Most other finite-element codes that model faults also include this
> feature. These tractions are calculated using the fault implementation, not
> from calculating the stresses within the volume elements. Alternatively, you
> can calculate the stress tensor on the face of a volume element and use the
> face normal to get a traction. However, in lower order finite-elements the
> stresses are not continuous across element boundaries (the displacement
> field is continuous but the strains and stresses are not).
>
> In most studies that I am aware of the Mohr-Coulomb criterion is applied
> locally using the shear and normal tractions. This accounts for potential
> spatial variation of the tractions due to loading, heterogeneous material
> properties, etc that cause failure on a subset of the fault.
>
> Regards,
> Brad
>
>
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