【摘要】 从TTI介质一阶应力—速度方程出发,利用旋转交错网格高阶有限差分方法,将非分裂完全匹配层(Non-spliting Perfect Match Layer,简称NPML)边界吸收条件和自由边界条件相结合形成组合边界条件,进行了二维三分量TTI介质弹性波场数值模拟。波场快照和炮记录表明:①采用非分裂式边界条件能较好地消除近地表大角度入射波和瞬逝波;②组合边界条件与NPML边界吸收条件相比,不仅有效地压制了边界反射,同时实现了对自由地表的模拟,获得了丰富的全波场信息,其中在地表产生的PS转换横波作为一种特殊的横波现象,可为近地表结构调查以及多波波场分析等提供有益信息;③自由地表引起的面波以及多次波对偏移结果有着重要影响,因此在实际地震资料处理中应当充分考虑自由地表条件对波场的影响效应。数值模拟结果证实了组合边界条件下二维三分量TTI介质波场数值模拟方法的可行性和正确性。更多还原

【Abstract】 In this work,based on the rotated staggered grid high-order finite-difference schemes of the first-order velocity-stress elastic wave equation,three-component elastic wavefield in the 2D TTI(Tilted Transverse Isotropy) media is simulated after combining NPML(Non-splitting Perfect Match Layers) absorption condition and the free-surface boundary condition.The snapshot and synthetic records illustrate: 1.The NPML absorption condition can efficiently attenuate near-surface incidence waves and evanescent waves;2.Comparison with the NPML absorption condition,the combined boundary conditions not only attenuate boundary reflections,but also accurately simulate free-surface situation and obtain full waves seismic data.Among these waves,PS converted wave as a special phenomenon provide useful information for the near surface structure investigation and multi-wave wavefield analysis;3.Rayleigh surface wave and surface multiples generated in the free-surface boundary have an important influence on seismic imaging,thus the free surface condition should be taken account in seismic data processing.The simulation results indicate the numerical simulation of elastic wavefield in the 2D TTI media based on the combined boundary conditions is feasible and valid.更多还原