Wave-equation reflection traveltime inversion with dynamic warping and hybrid waveform inversion

In reflection seismology, full waveform inversion (FWI) can generate high-wavenumber subsurface velocity models but often suffers from an objective function with local minima caused mainly by the absence of low frequencies in seismograms. These local minima cause cycle skipping when the smooth low-wavenumber component in the initial velocity model for FWI is far from the true model. To avoid cycle skipping, we propose a new wave-equation reflection traveltime inversion (WERTI) to update the low-wavenumber component of the velocity model, while using FWI to only update high-wavenumber details of the model. A hybrid waveform inversion (HWI) is then implemented by using WERTI and FWI alternatively. The hybrid waveform inversion mitigates the velocity-depth ambiguity and can recover subsurface velocities using only highfrequency reflection data.