Elastic Gaussian-Beam Migration for PP and PS Imaging Using Single-Component Seismic Data

Multicomponent elastic Gaussian-beam migration (EGBM) is relatively accurate, efficient, and flexible. However, a large amount of land seismic data is recorded by single-component geophones, which means that only vertical ground motions can be measured. In this case, the multicomponent EGBM cannot be applied. Conventionally, the vertical component is simply interpreted as the P-wave to P-wave reflected waves (PP) component and migrated using an acoustic migration method. But in fact, the vertical component also records the shear wave information. To perform elastic migration using only vertical-component data (in cases where multicomponent data are not available), we propose a single-component EGBM method for PP and P-wave to S-wave reflected waves (PS) imaging. Based on the Kirchhoff-Helmholtz integral, we give an effective formula for the downward extrapolation of multimode waves. Using our method, different wave modes are separated during migration by applying a decomposition vector to single-component data without prior data separation, resulting in better elimination of crosstalk artifacts and lower processing costs. Numerical experiments on 3-D land seismic data and 2-D vertical seismic profile (VSP) data are provided to demonstrate the performance of the method. Results show that PS-wave imaging is also feasible when we only have vertical-component data.