Enhance dynamic-warping for FWI to mitigate cycle-skipping

We put forward an optimized process in which dynamic warping is repeated with offset dependent constraint to ensure the traveltime difference reliable for the inversion. With the better reliably detected time-shifts, we can better manage the cycle-skipping problem when starting at a relatively higher frequency. The synthetic data from the Marmousi model as well as one challenging OBC dataset from Indonesia are used to demonstrate this method.