# Nonlinear convergence problem with static friction fault

I want to know the strike and dip of vertices on fault. And I obtain the *_info.h5 file about these informations. But I can’t figure out the values, for example, there is array with 339 rows and 3 columns in the ‘/vertex_fields/strike_dir’. The 339 rows are corresponding to the number of all vertices. Do the 3 columns represent the x, y, z directions? And these values in the range of -1~1 don’t looks like angles.
Thanks.

The `strike_dir` vector is the direction of the along-strike vector in global coordinates. The components will be in the range [-1, 1]. If the fault strike is aligned with the x-coordinate direction the `strike_dir` will be (1, 0, 0). If the fault strike is aligned with the y-coordinate direction, the `strike_dir` will be (0, 1, 0). The `dip_dir` is the direction of the dip vector in global coordinates. A vertical fault with have an `dip_dir` of either (0, 0, 1) or (0, 0, -1), depending on the direction of the fault normal. You can compute the fault strike and dip angles from these vectors.

Thanks，I’ll try it.

I add three fault in my 3d model using planar fault for simplicity (the first picture). And the simulation with the single gyf fault can run to completion when I set the friction coefficient to 0 and don’t specify the buried edge. Whereas, the simulation with single klf or lmsf fault and no specified buried edge can’t run, the nonlinear residual norm can’t converaged and become larger and larger. Why does the planar fault also have the kind of problem? I try to reduce the time step and smooth the fault surfaces according to your advice, but it doesn’t work.

I figure the slip rate of the gyf fault along strike. Then I find the location of fault nodes changes after run the simulation (the second picture). Then, I try the simulation with specified buried edge, the node location doesn’t change. Is this the problem with the buried edge? The slip on the fault will decrease if I specify buried edge, so I don’t want to specify it. How to fix it?

Thanks.
Chen

From your diagram, I am unable to determine the geometry for each fault. Do the faults klf and gyf cut through the entire domain (all edges are on the boundaries of the domain)? If so, then this is probably the source of the problem.

Are you sure this is a reasonable boundary value problem to solve to answer your science question? Normally, we solve boundary value problems with the fault embedded in the middle of the domain to avoid undesirable affects from truncating the boundary.