Multi-modal surface wave inversion and application to North sea OBN data

Surface wave inversion (SWI) for S-wave velocity plays an important role in near surface characterization and PS-wave velocity model building for depth migration. A hybrid approach is proposed to reduce non-linearity for multi-modal inversion without a-priori identification of higher order modes. This method is applied to north sea OBN data and produce a shallow Vs model that penetrates 120m depth below seabed. Vp/Vs ratios are then calculated as a powerful tool for near-surface characterization. SWI provides a high-resolution shallow Vs model which complements the weakness of PS-wave tomography in illuminating the near surface.