Comparison of refraction inversion methods

Bernard Law and Daniel Trad

ABSTRACT

Near surface weathering statics correction are traditionally done using first arrival times. Generalized Linear Inversion (GLI) and refraction tomography are two commonly used methods. Both GLI and refraction tomography are ray based method and require velocity to varies slowly. Furthermore, GLI uses the delay time concept and requires layered medium with velocity varies slowly in the lateral direction only. Refraction tomography is based on ray traced refraction ray paths and can handle more complex near surface geology. Both algorithms can include model weight and data weight in the cost function to incorporate reflection residual statics measurements. The modified GLI and refraction tomography cost function can improve the stability of the solution; however, the methods use first arrival travel time picks and are limited by the high frequency asymptotic approximation. Full waveform inversion (FWI) updates the velocity model by minimizing the misfit between the recorded field data and the modeled wavefield. FWI can provide higher resolution model than ray theory based methods. We compare Both GLI and refraction tomography methods using synthetic model and field data. We also review the full wave form inversion method and use synthetic model to demonstrate its potential and limitations for refraction inversion.

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