Full-waveform velocity and impedance inversion using OBN and DAS-VSP data

We propose a high-precision velocity modeling and imaging method that jointly utilizes OBN and DAS-VSP data. DASVSP records axial strain rates, which are challenging to integrate directly into full-waveform inversion (FWI). Conventional approaches convert DAS-VSP data into velocity components, introducing assumptions and approximations that that can lead to errors. To overcome this limitation, we present a novel method that directly simulates strain rate components under the acoustic wave equation using virtual dipole sources while accounting for the gauge length effect in DAS measurements. This approach reconstructs observed DAS data with high accuracy, eliminating errors associated with conventional data conversion. We applied the proposed method to a joint OBN and DASVSP survey conducted in the East China Sea. The combined use of OBN and DAS-VSP data mitigates parameter tradeoffs, enhances constraints on vertical velocity and anisotropy, and enables precise inversion of depthdependent Q models. Leveraging the derived anisotropic velocity and Q models from FWI, we performed impedance inversion on the raw data. The resulting impedance model effectively suppresses multiples and compensates for highfrequency losses due to the Q effects. These results demonstrate the method’s potential to enhance FWI applications, reduce inversion uncertainty, and provide significant theoretical and practical benefits.