A computer-implemented method for determining an image of a surveyed subsurface, the method comprising: receiving recorded wave fields D recorded with seismic sensors over the subsurface; generating a series of modified recorded wave fields D n based on the recorded wave fields D; iteratively applying an objective function F i to one element D i of the series of modified recorded wave fields D n and predicted wave fields P mi, where "i" is an index associated with a given iteration; calculating with a computing device an updated velocity model m i+1 based on a previous velocity model m i; and producing the image of the subsurface based on the recorded wave fields D and the updated velocity model m i+1, wherein the predicted wave fields P mi are predicted by the previous velocity model m i, wherein the step of generating a series of modified recorded wave fields D n further comprises applying a dynamic warping method for determining travel time differences τ between the predicted wave fields P mi and the recorded wave fields D, said method being characterized in that in said calculating step, said updated velocity model m i+1 is also based on a step length and in that said method further comprises: estimating a maximum travel time difference T from the travel time differences τ; defining an integer N based on the maximum travel time difference T and a dominant frequency f of the recorded wave fields D; and calculating the series of modified recorded wave fields D n as being the recorded wave fields D in which a time t is shifted with a product of a function of N and n and the travel time differences τ, wherein n is another integer. receiving recorded wave fields D recorded with seismic sensors over the subsurface; generating a series of modified recorded wave fields D n based on the recorded wave fields D; iteratively applying an objective function F i to one element D i of the series of modified recorded wave fields D n and predicted wave fields P mi, where "i" is an index associated with a given iteration; calculating with a computing device an updated velocity model m i+1 based on a previous velocity model m i; and producing the image of the subsurface based on the recorded wave fields D and the updated velocity model m i+1, wherein the predicted wave fields P mi are predicted by the previous velocity model m i, wherein the step of generating a series of modified recorded wave fields D n further comprises applying a dynamic warping method for determining travel time differences τ between the predicted wave fields P mi and the recorded wave fields D, said method being characterized in that in said calculating step, said updated velocity model m i+1 is also based on a step length and in that said method further comprises: estimating a maximum travel time difference T from the travel time differences τ; defining an integer N based on the maximum travel time difference T and a dominant frequency f of the recorded wave fields D; and calculating the series of modified recorded wave fields D n as being the recorded wave fields D in which a time t is shifted with a product of a function of N and n and the travel time differences τ, wherein n is another integer. estimating a maximum travel time difference T from the travel time differences τ; defining an integer N based on the maximum travel time difference T and a dominant frequency f of the recorded wave fields D; and calculating the series of modified recorded wave fields D n as being the recorded wave fields D in which a time t is shifted with a product of a function of N and n and the travel time differences τ, wherein n is another integer.