复杂地表条件下保幅高斯束偏移

高斯束偏移是一种准确、灵活、高效的深度域成像方法,其不但具有接近于波动方程偏移的成像精度,还保留了Kirchhoff偏移灵活、高效的特点以及对复杂地表条件良好的适应性.本文提出了一种适用于复杂地表条件的且具有相对振幅保持特点的高斯束偏移方法.通过考虑地表高程、倾角以及实际的道间距等信息,推导了基于高斯束表示的波场反向延拓公式,并结合反褶积成像条件,得到了复杂地表条件下的共炮域保幅高斯束偏移公式.同原有方法相比,本文方法不但可以直接在起伏的地表面进行局部平面波的分解,具有更高的成像精度,而且可以得到反映地下随角度变化反射系数的成像结果.数值模型的试算验证了上述结论.

Amplitude-preserved Gaussian beam migration under complex topographic conditions

Gaussian beam migration is an accurate,flexible and efficient depth migration method.It not only has the imaging accuracy approaching that of wave equation migration,but also retains many advantages of Kirchhoff migration,such as flexibility,efficiency and adaptability to complex topography.In this paper,we propose a Gaussian beam migration method which can easily accommodate complex topography and relatively preserve amplitude.By taking account of elevations,dip angles and actual trace intervals of topography,we derived an inverse wavefield extrapolation formula in terms of Gaussian beams,then combined it with deconvolution imaging conditions to obtain an amplitude-preserved shot domain Gaussian beam migration formula.Comparing to the original method,our method not only can decompose local plane-wave components directly from the complex topography to improve the imaging quality,but also can get migrated result which gives a direct measurement of the angle-dependent reflection coefficient.Trials of numerical models proved the above conclusions.