边界元法模拟含随机分布裂纹介质中波的传播
|
摘要
利用二维弹性动力边界积分方程解决了地震波在含裂纹介质中的散射问题。给出了二维空间中裂纹呈平均分布、正态分布和指数分布模型图。从记录到的波场散射图看到,裂纹不同空间分布会导致散射特性的极大不同。而且,当裂纹横向长度不变,纵横比增加时发现,波场通过该裂纹区时能量被俘获的更多,波传播持续时间更短,衰减更快,但由于这种分布能量更容易集中,使得波通过裂纹区后产生了较强的局部能量。
The problem about scattering of elastic waves by cracks or inclusions is important especially in seismology and geophysics.Numerical modeling of seismic data has long been recognized to be a powerful interpretive tool for understanding the complicated wave propagation.In this paper,a 2D BEM program was used to model seismic waves excited by a point explosive source propagating in the media with randomly distributed cracks.The accuracy of the method was well checked by means of computing waves propagating in the medium without any cracks with the corresponding theoretical solution.It was shown by the first example that different spatial distributions of the same scatters led to different wavefield characteristics.The effects of aspect ration of cracks with the same spatial distribution was shown in the second example.It was concluded that a lot of energy was trapped in areas with crack clustering.When the size of the clusters were small,most of the energy would propagate through the whole model,and high clustering would result in more attenuation when waves passed through the areas.With increasing of the aspect ration of cracks,the attenuation increased but some local energy might be concentrated.
The problem about scattering of elastic waves by cracks or inclusions is important especially in seismology and geophysics.Numerical modeling of seismic data has long been recognized to be a powerful interpretive tool for understanding the complicated wave propagation.In this paper,a 2D BEM program was used to model seismic waves excited by a point explosive source propagating in the media with randomly distributed cracks.The accuracy of the method was well checked by means of computing waves propagating in the medium without any cracks with the corresponding theoretical solution.It was shown by the first example that different spatial distributions of the same scatters led to different wavefield characteristics.The effects of aspect ration of cracks with the same spatial distribution was shown in the second example.It was concluded that a lot of energy was trapped in areas with crack clustering.When the size of the clusters were small,most of the energy would propagate through the whole model,and high clustering would result in more attenuation when waves passed through the areas.With increasing of the aspect ration of cracks,the attenuation increased but some local energy might be concentrated.
引文
[1]奚先,姚姚.二维随机介质及波动方程正演模拟[J].石油地球物理勘探,2001,36(5):546–552.(XI Xian,YAO Yao.2-D random media and wave equation forward modeling[J].OGP,2001,36(5):546–552.)
[2]LIU E,ZHONG Zhong-jie,NIU Bin-hua.BEM simulation of multiple scattering of elastic waves by cracks[J].Proc Int Conf Boundary element Techniques,1999,7:59–66.
[3]BENITES R,AKI K,YOMOGIDA K.Multiple scattering of SH waves in 2-D midia with many cavities[J].Pure Appl Geophys,1992,138:353-390.
[4]POINTER Liu E,HUDSON J A.Numerical modeling of seismic waves scattered by hydrofractures:application of the indirect boundary element method[J].Geophys J Int,1998,135:289–303.
[5]CHEN Gen-meng,ZHOU Hua-wei.Boundary element modeling of nondissipative and dissipative waves[J].Geophysics,1994,59:113–118.
[2]LIU E,ZHONG Zhong-jie,NIU Bin-hua.BEM simulation of multiple scattering of elastic waves by cracks[J].Proc Int Conf Boundary element Techniques,1999,7:59–66.
[3]BENITES R,AKI K,YOMOGIDA K.Multiple scattering of SH waves in 2-D midia with many cavities[J].Pure Appl Geophys,1992,138:353-390.
[4]POINTER Liu E,HUDSON J A.Numerical modeling of seismic waves scattered by hydrofractures:application of the indirect boundary element method[J].Geophys J Int,1998,135:289–303.
[5]CHEN Gen-meng,ZHOU Hua-wei.Boundary element modeling of nondissipative and dissipative waves[J].Geophysics,1994,59:113–118.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心