PS-wave processing and S-wave velocity inversion of OBS data from Northern South China Sea

Abstract

Abstract It is very important to convert seismic data from the time domain to the depth domain so we can explain the geological information more obviously. This paper provides a method for time to depth conversion. PS-wave data from an Ocean bottom seismograph (OBS) survey of the Northern South China Sea was processed through the separation of PP and PS wavefields and the rotation of horizontal components. An inverse modeling of travel times was performed for the determination of the S-wave velocity (Vs). The migration section of the single channel seismic data was used to define the model horizons and to help control their geometry. Wide angle hydrophone data of OBS were used to determine the P-wave travel times and wide angle horizontal component data of OBS were used to determine the PS-wave travel times. The chosen travel times from various shots were inverted for P- and S-wave interval velocities using RayInvr , which calculates theoretical travel times via ray tracing. Damped least squares optimization is performed to fine-tune the fits between observed and calculated travel times. The achieved trends of the P-wave velocity (Vp) and Vs curves are similar and the velocity increases in the layer where gas hydrates are present.