基于Lowrank近似的TTI介质一步法qP波正演模拟

One-step qP-waves forward Modeling in TTI Media with Lowrank Approximation

近年来,基于Lowrank近似的qP波正演模拟受到广泛关注。通常的Lowrank近似两步法波场外推虽然也能消除伪横波干扰,但是两步法依赖一个实值的相位函数,且在大时间步长不适用。基于Lowrank近似的qP波一步法波场外推方法具有处理复值相位函数的能力,对相位函数进行改进,加入速度梯度项,并成功应用于TTI介质qP波正演模拟。通过试验可知:基于Lowrank近似的一步法波场延拓具有传统两步法的优点,无伪横波干扰,在大时间步长波传播时比两步法更加稳定;各向异性情况下,一步法波场外推适用于任意倾角情况下,波场模拟结果清晰准确,没有发生不稳定。

Forward modeling of quasi-P-waves （qP） in TI medium for practical application draw great attention in recent year. Lowrank two-step wave field extrapolation can eliminate the SV-wave artifacts interference, but the two-step method relies on a real-valued phase function and cannot use in large time step. For this reason, we propose qP wave one-step wave field extrapolation method based on Lowrank approximation, One-step method has the ability to handle complex-valued phase functions, we add velocity gradient term to the phase function, and successfully applied in TTI media qP wave forward modeling. By experiment shows： One-step wave field extrapolation has the advantage the traditional two-step process, no SV-wave artifacts. One-step method is more stable in the large time step, and can reduce computing costs. In the case of anisotropic, the one-step wave field extrapolation applies to any inclinations, and the result of wave field simulation is clear and accurate, with no instability.