Research on Elastic Wave Reverse Time Migration Method for Single Component Data

The seismic waves propagating in actual earth media include longitudinal and transverse waves, which are coupled together and have vector characteristics of multi-wave and multi-component. At present, land seismic data generally only collects vertical components and approximates them as longitudinal waves, which has strict assumptions and prerequisites. This does not meet the actual situation. Even for single component seismic data, the seismic waves propagating underground are still vector waves with multi-wave and multi-component, and it is necessary to consider their vector characteristics when processing. To solve this problem, this paper develops an elastic wave reverse time migration (ERTM) imaging method for single component data. First, considering the characteristics of low shear wave velocity in the low deceleration zone, based on the assumption of elastic media, a theoretical model of overlying shear wave zero velocity layer + underlying fully elastic body is constructed, and based on this, a scalar-elastic coupled wave equation is established, which is more consistent with the actual process of seismic wave propagation, simultaneously suitable for conventional single component data. Then, the scalar-elastic coupled wave equation is used to carry out forward and backward continuation based on single component data to obtain the elastic vector wave field of underground multi-wave and multi-components, and Helmholtz decomposition is carried out for the vector wave field of forward and backward continuation to obtain the pure wave type underground P and S wave field. Finally, vector imaging conditions are applied to the forward and backward continuation wave field of pure wave type to obtain a multi-wave imaging profile. Application tests were conducted on typical models, and high-quality multi-wave imaging profiles were obtained based on conventional collected single component data, verifying the correctness and effectiveness of the method proposed in this paper.