“…Then, the scalar step is selected to obtain an appropriate amplitude of the updates, using linesearch algorithms, e.g., [59,17]. In our implementation, we also avoid the computation of the Hessian such that, at each iterations of the minimization, one must 1. solve the forward problem using the current model parameters, 2. compute the gradient of the misfit functional, Non-linear minimization suffers from local minima, which cannot be avoided with the deterministic approach, see, e.g., [15,69,8,33] in the context of seismic. We can mention the use of statistical-based methods but in the large-scale applications we have in mind, such approaches remain unusable at the moment.…”