变时间步长有限差分法逆时偏移

Finite-difference method with variable time-steps for reverse-time migration

逆时偏移因其可以利用多次波和回转波等信息,不受倾角限制对构造进行成像而逐渐成为一个研究的热点.但相对极低的计算效率,成为限制其实际应用的瓶颈之一.针对该问题,本文提出了一种时变的计算范围及可变时间步长的思路,即在不同的时间段内利用不同的时间步长计算相应空间范围内的波场,从而在算法上节省大量的计算时间.该思路简单易行,本文将其应用于有限差分法逆时偏移;通过对理论模型数据进行处理,证明该方案不影响波场计算的精度,并且可以在一定程度上提高计算的效率.

Two-way wave equation based reverse-time migration（RTM） is a quite attractive seismic imaging method, because it does not have the angle limitation of one-way propagators and can image the steeply dipping structures using multiples and overturning waves. But this method is expensive and not easy to compute in real applications. In this paper, we present a method to reduce the computational cost. According to the character of wave propagation, for a special span, we calculate the wave field only in a part of the whole space using a local time step. By processing of synthetic data, we show that this method does not alter the computational precision of the wave field, and can speed up the processing obviously.