Multimode inversion of Rayleigh waves using vertical and horizontal component data

Multimode inversion of surface waves improves S-wave velocity estimations. In surface wave analysis, only vertical components of the P-SV wavefield have been conventionally used to extract multimode Rayleigh waves. In this study, horizontal components of the P-SV waves were analyzed to extract additional mode information of Rayleigh waves. First, we extracted Rayleigh waves from vertical and horizontal components of the numerically synthesized P-SV waves. Additional mode information of Rayleigh waves could be obtained from horizontal component data. We then estimated S-wave velocity structures by multimode inversion using a genetic algorithm. Inclusion of dispersion curves from horizontal component data improved the investigation depth of Swave velocity estimation. Next, multimode Rayleigh waves were extracted from three-component seismic data acquired in Alberta, Canada. By including dispersion curves from horizontal component data, which have different mode information from those from vertical component data, the inverted S-wave velocity structures agreed well with logging data for deeper layer. Therefore, inclusion of horizontal component data of the P-SV wavefield makes it possible to extract additional mode information of Rayleigh waves, thus eliminating ambiguity from S-wave velocity estimations in multimode inversions.