SE2.3 Elastic Wavefield Decomposition

Surface multi-component seismic land data are presented in terms of particle velocities measured on a stress free surface due to multi-component sources. We show that it is possible for any inhomogeneous ubsurface to decompose the wave fields both at the source and receiver side. This enables us 10 represent the seismic data in terms of upgoing P or S waves reaching the surface due to a pure P or S wave source. ln case of a homogeneous near surf;lce layer the decomposition can be done in the frequency-wavenumber domain (w,k,,k,). Like in the migration process, in case of lateral velocity variations it is preferable lo work in the frequency-space domain (w,x,y); in this domain decomposition can he described in terms of lateral convolution. To do a correct wave field decomposition we have to know the P and S wave velocity in the near surface layer. If this information is not available, it is possible to estimate them in an iterative way from the ‘wave field ilecomposirion results. The birefringence study, usualiy tiwr iw Itie horizontal particle displacements, should preferably be done on the decomposed S, and S, wave fields