煤层转换波的数值模拟及应用

Numerical modeling of coal converted waves and its application

（1. 中国煤炭地质总局，北京 100039;2.中国矿业大学，北京 100083）

（China National Administration of Coal Geology; Beijing 100039; China）

从弹性波动方程出发，在交错网格空间中采用高阶有限差分技术导出了应力-速度弹性波动方程正演的差分格式，研究了其吸收边界条件与数值频散关系，建立了煤田多波勘探的数学模型。在此基础上通过对特定模型的数值模拟，研究了纵波震源激发条件下弹性波在地下的传播规律与煤层多波记录的波场特征。数值模拟结果表明,当地表不存在低速层时，煤田多波记录的X分量与Z分量上均有纵波与横波存在，因此在资料处理中必须首先进行波场分离工作。在一定的厚度范围内，煤层转换波的能量还与煤层厚度有关。故在进行野外资料采集观测系统设计时，要综合考虑转换波和纵波的观测范围。

Based on elastic wave equation, a high-order finite-difference scheme was derived in staggered grid space, and the relation between absorbing boundary conditions and numerical dispersion was also studied to establish the mathematical model of coal multi-component seismic exploration. By modeling typical geology, this paper studied the propagation regularity of elastic waves and the wave-field characteristics of multi-component seismic waves. Modeling showed that there are longitudinal waves and shear waves in both X and Z components if there is no low velocity layer in near surface. This suggests that separation of waves should be implemented at the very beginning of data processing. The result also showed that the energy of converted waves changes with thickness of coal within a certain range, which indicates that the observing range of converted waves and longitudinal waves should be taken into account when designing layout.