>>> STEP (UNSCALED): max_step
This command defines the maximum allowable size of the scaled (fi = σpi, default; fi = pi; keyword CURRENT) or unscaled (fi = 1, keyword UNSCALED) update vector Δp per iTOUGH2 iteration. The step length of the scaled parameter update vector is defined as follows:
This is a global step size limitation as opposed to the one specified for each individual parameter (see command >>>> STEP). Limiting the global step size may make the inversion more stable. Parameter max_step should be chosen large enough, so that the size of the proposed step size |Δp| is reduced to |Δpmax)| only during the first few iterations. The figure below illustrates that limiting the step size maintains the direction of the step taken in the parameter space.
>>> number of ITERATIONS : 10 (may need more iterations!)
>>> limit scaled STEP size to: 1.0 [dimensionless]
>>>> STEP (p)