【摘要】 本文通过弹性波方程交错网格有限差分正演,模拟了地震波在二维弹性随机介质中的传播,得到了球面波传播的单炮记录和波场快照以及平面波自激自收记录。为了考察二维弹性随机介质的波场特征,将平面波自激自收记录分成直达波区、散射波区、反射波区三个区域,并在三个区域中分别计算了能量相对值、主频、有效频带宽度三个特征量。通过研究这三个特征量与随机介质模型的自相关长度、粗糙度因子、扰动标准差等因素的关系,得到以下结论:直达波、散射波、反射波的能量相对值随随机介质模型自相关长度、粗糙度因子、扰动标准差以及震源主频的变化有明显的变化。直达波的主频和频带宽度受这些因素的影响很小;散射波的主频主要受自相关长度的影响,散射波的有效频带宽度很窄,受各因素影响也很小;反射波的主频随自相关长度、粗糙度因子、扰动标准差的变化有明显的变化,而反射波的频带宽度主要受扰动标准差的影响。更多还原

【Abstract】 With the staggered-grid finite-difference forward modeling of wave equation,we simulate seismic wave propagation in 2-D elastic random medium,obtain seismograms and snapshots of the propagation of spherical wave,and zero offset records of plane wave.In order to study wave field characteristics in 2-D elastic random medium,we divide the records of plane wave into three different time segments:direct wave segment,scattered wave segment and reflected wave segment.And we calculate three statistical characteristic values of three different time segments:relative value of wave field energy,dominant frequency and bandwidth.By studying the relationship between the three statistical characteristic values and autocorrelation length,roughness factor and disturbance standard deviation of the random medium model,we get the following conclusions:with the changes of autocorrelation length,the relative value of wave field energy of direct wave,scattered wave and reflected wave changes significantly.The dominant frequency and bandwidth of direct wave have little effect by these factors.The dominant frequency of scattered wave is mainly affected by the autocorrelation length.However,the bandwidth of scattered wave is very narrow,and has little effect of the factors.The dominant frequency of reflected wave changes significantly versus the factors such as autocorrelation length,roughness factor and disturbance standard deviation,and the bandwidth of the reflected wave is mainly affected by the standard deviation of disturbances.更多还原