摘要
在实际中常遇到一类含有低速层的介质,其频散曲线在感兴趣的频率范围并无视觉上的交叉现象,也无明显的低速层指示。针对此类介质,基于地震反射资料中的面波信息,综合实例和数值模拟进行分析,结果显示:如果观测的基阶模式频散曲线不包含对低速层深度敏感的频段,单独基于基阶模式的频散曲线可能无法恢复模型的低速特征;但如果同时利用相同频段的多阶模式信息,即使观测的频散曲线没有明显的低速特征指示,也可以通过多模式频散信息反演重建模型的低速特征。
Due to high sensitivity to S-wave velocity,Rayleigh-wave dispersion curves of the fundamental and higher modes are usually used to invert near-surface S-wave velocities in engineering geophysical exploration.For the model containing a low-velocity layer,the disper-sion curves of the fundamental and higher modes show two typical characteristics.One typical characteristic is that the crossover would be observed between different modes,and the funda-mental mode shows obvious indication of low-velocity characteristics in interested frequency ranges.For the other kind of model with low-velocity layers,the dispersion curves have no visual crossing phenomenon in the frequency range of interest,and the low-velocity character-istics may not be observed in the measured dispersion curves.For the latter model containing a low-velocity layer,which is often encountered in practice,investigations on the inversion of multi-mode Rayleigh waves are conducted in this paper based on seismic reflection data.The studies show that if the observed fundamental-mode dispersion curve does not include the frequency band sensitive to the depth of the low-velocity layer,the inversion based on the fundamental-mode alone may not be able to recover the low-velocity characteristics of the model. But the low-velocity layer can be reconstructed accurately by inversion considering both the fundamental and higher mode Rayleigh waves even the observed fundamental mode disper- sion curve has no obvious indication of low-velocity characteristics.
作者
冯宣政
鲁来玉
王少曈
秦彤威
Feng Xuanzheng;Lu Laiyu;Wang Shaotong;Qin Tongwei(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)
出处
《地震学报》
CSCD
北大核心
2023年第2期203-222,共20页
Acta Seismologica Sinica
基金
国家自然科学基金地震联合基金(U1839209),国家自然科学基金(41674062)共同资助
国家重点研发计划(2017YFC1500200)。
关键词
高阶瑞雷面波
反演
低速层
频散曲线
浅层地震反射
higher-mode Rayleigh waves
inversion
low-velocity layer
dispersion curves
shallow seismic reflection
