Multi-parameter full waveform inversion using only the streamer data based on the acoustic-elastic coupled wave equation

Abstract

The ocean seismic pressure data observed by hydrophones contain the elastic information of the subsurface medium, although few studies of full waveform inversion (FWI) regard the pressure data as generated from elastic media. Based on the acoustic-elastic coupled equation, which can directly obtain the elastic pressure component, we propose an acoustic-elastic FWI (AEFWI) method to use elastic pressure data. First, we illustrated the similarities and differences in wave propagation in acoustic and elastic media using ocean-bottom models. Furthermore, we compared the effect of pressure data with different degrees of elastic effects on acoustic FWI (AFWI) and AEFWI. It was found that the S-wave velocity at the seabed interface had a significant effect on the AFWI. When the seabed is soft, the results of AFWI are acceptable, whereas when the seabed is hard, the results of AFWI are nearly wrong, and the presence of elastic effects has to be considered in the inversion at this time. Contrastingly, the proposed method can obtain more accurate P- and S-wave velocities using only pressure data. Finally, the proposed method was applied to a real streamer dataset of the East China Sea, and high wavenumber P- and S-wave velocities were obtained. The RTM images illustrated the accuracy of the inversion results.