旋转时空双变网格有限差分地震波场正演模拟

在交错网格有限差分算法中,模型网格剖分原则与正演计算效率密切相关.当模型存在小型非均质体或者低降速层等情况,为保证精度,满足稳定性条件,需缩小网格步长,导致局部过采样,计算效率低下.为保证模拟精度的同时保持高计算效率,通常采用变化的空间网格与时间步长相结合的高阶有限差分模拟方法对波场进行模拟.然而,时空双变算法存在着交错网格固有缺点,在模拟非均匀性较强的复杂介质波场传播时,需对介质参数进行平均或内插.同时,该算法在空间与时间上的变网格实现极为复杂.为压制变网格引起的虚假反射,提升模拟精度和计算效率,本文在时空双变网格算法的基础上,采用旋转差分角度的方式,提出了旋转时空双变交错网格算法.该方法既保留了旋转网格和双变网格的优势,又简化了时空双变算法流程,更利于推广和应用.

Modeling seismic wave propagation with rotated staggered dual-variable grid

In the staggered grid finite difference algorithm, the model mesh generation principle is closely related to the forward calculation efficiency. When there are small inhomogeneous bodies or low deceleration layers in the model, in order to ensure the accuracy and meet the stability conditions, it is necessary to adopt small grid step size, resulting in local oversampling and reducing the calculation efficiency. In this paper, the wave field is simulated by the high-order finite difference simulation method combining the variable spatial grid and time step length. However, the spatiotemporal dual-variable grid algorithm has the inherent disadvantages of staggered grid. When simulating the wave field propagation of complex medium with strong heterogeneity, the medium parameters need to be averaged or interpolated. At the same time, the variable grid implementation of the algorithm in space and time is very complex. In order to suppress the false reflection caused by the variable grid and improve the simulation accuracy and computational efficiency, this paper proposes a rotating spatiotemporal double variable interlaced grid algorithm based on the spatiotemporal double variable grid algorithm and by means of rotating differential angle. This algorithm not only retains the advantages of rotating grid and double variable grid, but also simplifies the process of spatio-temporal double variable algorithm, which is more conducive to popularization and application.