起伏地表下的直接叠前时间偏移

Prestack time migration including surface topography

提出了一种新的叠前时间偏移方法和流程,可不必应用野外静校正,直接对起伏地表采集的地震数据进行叠前时间偏移.本文采用输入道成像方式,通过基于稳相点原理给出单道数据的走时和振幅计算方法,发展了一个表驱动的叠前时间偏移算法.偏移方法可依据同相轴是否被拉平确定叠加速度和修正近地表速度模型,也可依据拟成像的构造倾角,自适应地确定偏移孔径;后者既减少了偏移计算量,也压制了偏移噪声.文中用二维起伏地表的断陷盆地模型的理论数据验证了所发展方法的成像效果.

We present a pre-stack time migration scheme and workflow that can image land seismic data without field statics corrections.The scheme uses a ＂spread＂ imaging method.The travel times and amplitudes for computing the impulse response of each trace are obtained using the stationary-phase theory.This results in a table-driven migration algorithm.The proposed scheme can update the velocity model for both the stack velocities and near surface velocities with respect to the flats of the events.We also adaptively determine migration aperture according to the dips of the imaging structures.This reduces the computational cost and suppresses the migration noises.A synthetic dataset,which is generated using acoustic finite-difference for a rift-subsidence basin including 2-D irregular surface,is used to demonstrate the scheme.