ANALYSIS OF COMBINED EXCITATION EFFECT OF SHEAR-WAVE VIBROSEIS

Limited by the vibrator structure, there are some problems such as low down-going earth energy and shallow down-going depth of shear-wave signals when the shear-wave vibroseis is excited. Therefore, the influence of different combinations of shear-wave vibroseis vibrators on the excitation effect was innovatively studied through the three-dimensional finite element numerical simulation. Firstly, based on three-dimensional nine-component data and two types of combinations, eight modes of vibration excitation of combined shear-wave vibroseis were considered, a vibrator-earth finite element model was established, and an evaluation system of the vibration excitation effect of the combined shear-wave vibroseis was constructed. Secondly, based on this evaluation system, the influence of the various combined excitation modes of the shear-wave vibroseis on the downward energy of the earth, the downward depth of shear-wave signals and the mutual interference between combined excitation waves was analyzed in detail. The results show that, compared with a single shear-wave vibroseis, when two SHY shear-wave vibroseises are arranged side by side for the normal excitation, the incoming earth energy is increased by 86.36%, and the displacement amplitude of earth particles is increased by 73.40% on average. When two SHX shear-wave vibroseises are excited in the normal direction, the incoming earth energy increases by 97.48%, and the displacement amplitude of earth particles increases by 58.61% on average, which greatly improves the excitation effect. The research results can provide the guidance for improving the excitation effect of the shear-wave vibroseis and the reference for the design of combined excitation mode of the shear-wave vibroseis.