Phase-amplitude-based polarized direct envelope inversion in the time-frequency domain

Abstract

Large-scale geologic structures with strong contrasts present difficulties for seismic imaging and inversion. Previously, direct envelope inversion (DEI) with ultralow frequency has been proposed to retrieve strong-contrast velocity models. However, the envelope signals lose the instantaneous phase of the original wavefield, resulting in erroneous seismic inversion results. To solve this problem, the instantaneous phase of the wavefield is encoded into envelopes for DEI. In this way, a polarized envelope is created to contain both abundant low frequencies and the instantaneous phase information of the original seismic waveform. Furthermore, to improve the resolution of deep regions underneath the strong reflections, we propose a phase-amplitude-based polarized direct envelope inversion (PA-PDEI) misfit in the time-frequency domain that uses an amplitude factor to emphasize the phase information. This makes it possible to adjust the amplitude influence and boost the low-amplitude seismic signals for deep targets. Tests on a model with a salt body and on field data show that combining the PA-PDEI with the phase-amplitude-based full-waveform inversion (PA-FWI) make it possible to reliably reconstruct velocity models, especially for deep regions, despite large and strong perturbations.