Joint Traveltime and Waveform Envelope Inversion for Near-surface Imaging

In the linearized seismic full waveform inversion (FWI), it is well known that a good initial model is needed to avoid cycle-skipping issue, especially when the low-frequency components of data are lacking. To solve the problem, we develop a joint first-arrival traveltime and early arrival envelope inversion method (JTE) to build a good near-surface velocity model with low-wavenumber components. The JTE method combines the robustness of nonlinear traveltime inversion and the low-frequency information embedded in the waveform envelope. In two synthetic experiments, we confirm that traveltime inversion constrains the top near-surface velocity structures tightly, while the envelope inversion recovers the low-wavenumber structures with low-velocity objects or layers. Using the results of JTE as starting models, we find that FWI can produce accurate solutions for complex numerical models. In a real-data example, JTE followed by FWI resolves a near-surface velocity model to improve statics corrections for the subsurface stacking image.