弱连接界面地层地震反射波场的正演方法

Forward modeling of reflected wavefleld from strata with weakly bonded interfaces.

当介质中存在按照一定方向排列的裂隙时,会形成弱连接界面。地震波传播时,界面两侧的质点不再满足位移的连续性条件,位移差与该点的应力呈线性关系。界面的这种弱连接特性可以用法向柔量和切向柔量来表示,柔量值越大,界面的接触程度和质点位移的连续性就越差。讨论了界面柔量对PP反射波的影响,并通过数值算例说明了法向柔量对反射系数的影响大于切向柔量;建立了基于反射率法的弱连接界面地层地震反射波场正演方法;通过用正演方法合成的(τ,p)域地震记录,讨论了含有弱连接界面模型的波场特征,给出了(τ,p)域波场的动校正方法。模拟试验和动校正结果说明方法正确可行。

Weakly bonded interfaces can be formed when some aligned cracks exist in the media.The particles beside the interface don't satisfy the continuity condition of the displacement any more.The displacement difference has linear relationship with the stress of the point.The weakly bonded characteristic can be expressed by nor- mal compliance and shear compliance.With the increasing of inter- face compliances,the bonding level and the displacement continuity becomes poorer.The influences of interface compliances on PP wave reflections were discussed.Numerical models were utilized to illustrate that the normal compliance had much influence on PP re- flections than shear compliance did.A forward modeling method for reflected wavefield of strata with weakly bonded interfaces was developed based on the reflectivity method.The synthetic seismo- grams in (r,p) domain were obtained by this method,and the wavefield characteristics of weakly bonded interface models were discussed.Meanwhile,the NMO correction procedure in (r,p) domain was established.Simulated test and NMO correction re- suits show that the method is feasible and accurate.