I would like to ask about the orientation of the stress and strain tensor in PyLith result.
As previously, I have mentioned that I run the simulation of 2D subduction and put also a splay fault in the geometry. I would like to calculate the coulomb stress on this splay fault.
My question is, do the stress and strain tensor in Pylith already have orientation thus I can calculate the coulomb stress directly using the stress and strain tensor from the result? Or I should consider the geometry (strike,dip) of the splay fault manually and do post-calculation to retrieve the strain and normal traction?
The traction changes on the fault computed by PyLith are in the local fault coordinate system, and the components correspond to left-lateral shear, updip shear, and fault-normal stress (look in the PyLith manual for the order). These components may then be used to compute the Coulomb stress changes. You may also find it useful to use the orientation info provided in the fault_info file (strike_dir, dip_dir, normal_dir), which provides the orientation of the local fault surface in the global system.
Dear alvinakkuncoro,
I also want to calculate the Coulomb stress. If you have already figure it out from the traction and fault_info (strike_dir, dip_dir, normal_dir), would you like to tell me the method?
Thank you in advance.
Best Regards,
Peiyu
Dear willic3,
I also want to calculate the Coulomb stress (CFS).
I checked the fault_info file (strike_dir,dip_dir, normal_dir), but it doesn’t seem to be consistent with the results of the direction value that I calculated according to my formula ( δ,dip angle; φ, strike angle; λ， slip angle; 1. normal_dir: x= sinδ×cosφ, y= -sinδ×sinφ， z= cosδ ; 2. strike_dir: x= sinφ, y= cosφ, z=0; 3. dip_dir: x= cosφ×cosδ, y= -sinφ×cosδ, z= sinδ)
In addition, if Traction_change_Z (TZ) on the fault is in the direction of fault opening, it should be projected on the normal and slip direction of the fault, and the CFS can be calculated by the formula : CFS = TX×cosλ + (TY+TZ×cosδ)×sinλ - μ×TZ×sinδ ？
Please were you able to figure it out. I need to also estimate Coulomb stress and I used the stress tensors directly but the result seems a bit funny. Can you please share your method.