摘要
粘弹性介质的吸收特性与频率有关,在地震波的传播过程中高频成份比低频成份衰减得快。这就导致低频部分相对增加,使主频向低频方向移动。假设介质的品质因子与频率无关,地震波主频的偏移量与吸收系数对传播路径的积分成比例,则通过它们之间的关系可以估测介质的吸收系数。通过零偏VSP理论模型试算,证实了这种方法的可靠性。用主频偏移求取吸收系数和品质因子是在频率域中进行,利用快速傅氏变换,使得计算成本大大降低,并且不需要迭代求解,不用考虑收敛条件,因此具有较大的实用价值。
The attenuation of anelastic medium is dependent on frequency. The high-frequency components of seismic signals are attenuated more rapidly than the low-frequency components as seismic waves propagate. As a result, the low-frequency contents increase as the centroid of signal spectrum experiences a downshift. In case that frequency is independent on quality factor, the offset of the centroid frequency is proportional to the integral of attenuation factor along wavepath, thus can be used to reconstruct the attenuation distribution. Tests on synthetic zero-offset VSP data showed that the method is reliable. The proposed method is of practical value because it works in frequency domain, its computation cost can be greatly reduced through fast Fourier transformation.
出处
《勘探地球物理进展》
2006年第1期30-33,共4页
Progress in Exploration Geophysics
关键词
主频偏移
吸收系统
品质因子
零偏VSP
模型计算
frequency shift
absorption coefficient
quality factor
zero-offset VSP
modeling
