【摘要】 将真空法和旋转交错网格相结合,实现了地下空洞高阶旋转交错网格波场数值模拟,克服了旋转交错网格在模拟自由边界条件时只在空间二阶差分时稳定的不足。通过和已有普通交错网格下改进的真空法对比,验证了该方法的正确性和稳定性。为了减弱模型人工边界产生的反射,采用了吸收效果较好的完全匹配层技术。模拟了不同模型参数组合情况下的地震波传播以及地震波与地下空洞的相互作用,通过对比不同参数组合的地震记录和波场快照,以及包含空洞和不含空洞地震记录和波场快照,分析了地震波在地下存在空洞时的传播特征以及震源子波频率、地下空洞大小和埋深对地表地震记录的影响。更多还原

【Abstract】 We combined the improved vacuum formulation and the rotated staggered grid finite difference method to implement the high order rotated staggered finite difference elastic wave-field simulation at the presence of underground cavities.Our method overcame the defect of rotated staggered finite difference when modeling the free surface condition which is only stable at second order spatial FD operators,through the comparison with existing vacuum formulation testifies our methods accuracy and stability.The perfectly Matched Layer(PML)absorbing boundary condition is applied to decrease the reflection from the edges of the numerical model.Different seismograms are calculated with models without voids and models contain voids with different size and depth under different source wavelet frequency.The effects of different cavity size and depth and the source wavelet frequency are evaluated from the snapshots and seismograms with and without the cavity.更多还原