Free surface output
Velocities and ground deformations can be imaged as a surface representation, in a file that can be opened in ParaView. Threads or nodes can be dedicated to write this output (see Asynchronous Output), but it is usually not necessary. The output to enabled in the Output namelist:
&Output SurfaceOutput = 1 SurfaceOutputRefinement = 1 SurfaceOutputInterval = 0.5 /
SurfaceOutputRefinement = 0, one triangle is outputted for each
mesh cell. The unknowns are evaluated at the center of each cell.
SurfaceOutputRefinement = 1 subdivides each triangle, into 4
subtriangles. Higher SurfaceOutputRefinement would further subdivide
v1, v2, v3: ground velocities, x y and z componentsu1, u2, u3: ground displacements, x y and z components
Additionally, the writer outputs a quantity called “locationFlag”, which has the values 0 and 1 when at the elastic or acoustic side of an elastic-acoustic interface. In this way, we can distinguish between both sides of the interface even though they have the same coordinates. It has the value 2 for an ordinary free surface boundary condition and the value 3 for a free surface with gravity boundary condition. This value can be used to filter the output (which contains all these surfaces), for example using Paraview’s Threshold filter.