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正如可将由震源发射出的波场表示成一组高斯射束来建立合成地震数据那样,也可将记录的波场表示在地表出现的一组高斯射束,将所记录的数据向下延拓。在这两种情况下,当地震速度横向变化时,用高斯射束描述地震波的传播可能是方便的。高斯射束下延拓能实现波传播的波动方程计算,而仍然保留波传播可解释的射线路径特征。本文描述一种零炮检距的深度偏移方法,该方法使用记录波场的高斯射束下延拓。高斯射束偏移方法有助于复杂构造成象。像有限差分偏移那样,它尤其适用于速度横向变化的地方。不过,高斯射束偏移可使陡倾反射层成象且不会在速度模型的构造上产生多余的反射。不像其他射线路径方法,高斯射束偏移方法在焦散面和屏蔽面处保证正常响应。此外,本方法确保有效而又精确地计算射束间隔。高斯射束偏移所成的象通常是稳定的,不受射束参数变化的影响。
Just as the wave field emitted by the source can be represented as a set of Gaussian beams to create synthetic seismic data, the recorded wave field can also represent a set of Gaussian beams appearing on the surface, extending the recorded data downward. In both cases, it may be convenient to describe the propagation of seismic waves with gaussian beams when the seismic velocity varies laterally. Gaussian beam extension can achieve wave propagation wave equation calculation, and still retain the wave propagation can explain the ray path characteristics. This paper describes a zero offset depth offset method that uses Gaussian beam continuation of the recorded wavefield. The Gaussian beam migration method helps with the imaging of complex structures. Like finite difference offsets, it is especially useful where lateral velocity changes. However, Gaussian beam offsets allow the steeply reflecting layer to be imaged without creating extraneous reflections in the construction of the velocity model. Unlike other ray path methods, the Gaussian beam migration method ensures normal response at caustics and shield surfaces. In addition, this method ensures efficient and accurate calculation of beam spacing. The image created by Gaussian beam offsets is usually stable, independent of changes in the beam parameters.