Seismic Acquisition And Analysis In The Area Of High Velocity Shielding Layers

The discrepancy of high velocity layer and wall rock in wave impedance or in reflectivity is palpable, so it will come into being a strong reflector. If we adopt a normal method of seismic exploration, the high velocity will shield the energy of down wave, because the critical angle is very small and the full reverberation is easy, also it is difficulty for seismic wave strike the interface which we will explore. Moreover, the energy of the interference wave, such as multiple wave and refractive wave, are very strong. Based on Snell law and Zoeppritz equation and used the forward modeling in ray theory, this master's thesis have do some research on gathering the seismic data in the high velocity shielded layer area.Firstly we analysis the reflection coefficient and transmission coefficient of P-wave or SV-wave vary with the incidence angle under different condition. So we can ameliorate ways and means in seismic exploration according to the peculiarity of the high velocity shielded layer.Secondly this thesis study the wide-angel reflection, we can receive stronger energy with a long layout in the high velocity layer area. In this condition, it is inapplicable to NMO correction with normal method, so non-hyperbolic time-distance equation is required. In addition, this thesis also deduce the V_av or V_r will be accelerate along with the off-set.Finally based on the peculiarity of reflection and transmission we can receive comparatively stronger reflected SV wave, so it is feasible to explore with PS converted wave in the high velocity shielded layer area. This thesis has sought exactly the converted point in homogeneous medium by solving the cubic equation and quartic equation, it also analysis and compare one-parameter, two-parameter and three-parameter time-distance equation of PS converted wave. Moreover, it analysis the peculiarity of AVO.