Time‐Reversal Full Wavefield Inversion: From Waveform Misfit to Wavefield Focus

We introduce time‐reversal full wavefield inversion (TRFWI), a velocity‐model‐building method that replaces waveform‐misfit minimization with a physically motivated wavefield‐focusing criterion. The recorded data are reversed in time and backpropagated through a trial velocity model; the inversion objective is the degree to which the wavefield focuses on the known source position and onset time. This Research Note presents a proof‐of‐concept demonstration using a simple acoustic example. The focusing functional exhibits a clear maximum at the true velocity, confirming that time‐reversal focusing provides a viable alternative to classical full waveform inversion (FWI). Unlike waveform‐misfit objectives, the focusing criterion naturally incorporates the full recorded wavefield, including multiples and scattered energy as constructive information. Optimization strategies and field‐data applications will be addressed in a subsequent publication.