Abstract：Because prestack seismic data contain abundant both P-wave and S-wave information that are close relative to lithology,so more abundant and effective lithologic information can be obtained from inversion of prestack data in comparison with from ordinary poststack impedance inversion. Since propagating regularity of seismic wave in layered e-lastic half-space has condition simulating common AVO analysis,so a method based on elastic wave equation can be adopted to synthesize prestack records. The paper deduced the reflection formula formed by spherical wave in layered half-space that contains spreading effects of waveform,S-wave reflections in layered strata and reflections from free surface;taking the forward simulating algorithm as a basis,a set of prestack elastic wave equation inversion methods was built up,among which the solution of inversion problem was finished by genetic algorithm. The real implement of genetic algorithm was designed totally according to prestack inversion that is a certain optimized non-linear multi-parameters problem in order to effectively search optimum strata parameters. The P- and S-wave velocities and densities computed from prestack elastic wave inversion can be used to compute lithologic physical parameters such as Poisson ratio, elastic modulus etc., providing new tool for identifying fluid content in reservoir pores.
