The spatial autocorrelation(SPAC)(also known as the Aki’s spectral method)of ambient seismic noise has been widely adopted in surface wave phase velocity extraction.In two-dimensional cases,the surface wave velocity ...The spatial autocorrelation(SPAC)(also known as the Aki’s spectral method)of ambient seismic noise has been widely adopted in surface wave phase velocity extraction.In two-dimensional cases,the surface wave velocity can be calculated by fitting the SPAC coefficients with the zero-order Bessel function of the first kind or using the zeros of the Aki’s spectrum.This method has also been extended to active-source records.This study examined the application of the zeros of Aki’s spectra on active-source records using theoretical analysis and numerical simulation.We show that the zeros of the Aki’s spectrum should be associated with the zeros of the cosine function instead of the zeros of the zero-order Bessel function when extracting the phase velocity of the surface wave,considering the data acquisition and processing of the active-source records.The proposed method was then applied to the active-source data from methane explosion experiments collected using a dense array in Tongzhou,the subcenter of Beijing,for extracting the phase velocity of Rayleigh wave.The extracted dispersion curves were integrated with those obtained by beamforming the ambient noise to yield broadband dispersion curves at 0.3–6 Hz.This provides insightful results at high frequencies,at which less information can be obtained through the passive-source beamforming.The combing phase velocities from active-source with those obtained from ambient noise provide a better constrain on the shallow structure.Based on the combined fundamental mode dispersion curves at 28 excitation points,the S-wave velocity structure below the dense array is obtained by depth inversion.Due to the constraints imposed by the high-frequency information from active source,the estimated vS30 are more reliable and can be used to the site classification.展开更多
基于目前AVO(Amplitude Versus Offset)反演技术中所普遍使用的Aki-Richards和Shuey近似,以Zoeppritz方程的准确解为参照,针对几种典型油藏反射界面,计算了Aki-Richards和Shuey近似所产生的相对误差,绘出了相对误差随入射角的变化曲线....基于目前AVO(Amplitude Versus Offset)反演技术中所普遍使用的Aki-Richards和Shuey近似,以Zoeppritz方程的准确解为参照,针对几种典型油藏反射界面,计算了Aki-Richards和Shuey近似所产生的相对误差,绘出了相对误差随入射角的变化曲线.计算表明,在存在极性反转的反射界面,Aki-Richards和Shuey近似的计算结果会带来很大的误差,在极性反转点附近的计算结果失去它的可信性;在泥岩与气砂、油砂或水砂组成的反射界面,即便就是在小角度范围内也存在较大的计算误差(如泥岩—气砂反射界,入射角在5°之内,相对误差就超过了10%);在油砂和水砂反射界面Aki Richards和Shuey是很好的近似.本文对Aki-Richards和Shuey近似结合几种典型油藏反射界面给出定量的分析,为储层参数反演方案的设计特别是反演道集及范围的选择提供理论依据.展开更多
基金supported by the National Natural Science Foundation of China(No.42474081)the Fundamental Research Funds from the Institute of Geophysics,China Earthquake Administration(No.DQJB 23K34)the Science and Technology Department of Henan Province of China(No.242102320039).
文摘The spatial autocorrelation(SPAC)(also known as the Aki’s spectral method)of ambient seismic noise has been widely adopted in surface wave phase velocity extraction.In two-dimensional cases,the surface wave velocity can be calculated by fitting the SPAC coefficients with the zero-order Bessel function of the first kind or using the zeros of the Aki’s spectrum.This method has also been extended to active-source records.This study examined the application of the zeros of Aki’s spectra on active-source records using theoretical analysis and numerical simulation.We show that the zeros of the Aki’s spectrum should be associated with the zeros of the cosine function instead of the zeros of the zero-order Bessel function when extracting the phase velocity of the surface wave,considering the data acquisition and processing of the active-source records.The proposed method was then applied to the active-source data from methane explosion experiments collected using a dense array in Tongzhou,the subcenter of Beijing,for extracting the phase velocity of Rayleigh wave.The extracted dispersion curves were integrated with those obtained by beamforming the ambient noise to yield broadband dispersion curves at 0.3–6 Hz.This provides insightful results at high frequencies,at which less information can be obtained through the passive-source beamforming.The combing phase velocities from active-source with those obtained from ambient noise provide a better constrain on the shallow structure.Based on the combined fundamental mode dispersion curves at 28 excitation points,the S-wave velocity structure below the dense array is obtained by depth inversion.Due to the constraints imposed by the high-frequency information from active source,the estimated vS30 are more reliable and can be used to the site classification.
文摘基于目前AVO(Amplitude Versus Offset)反演技术中所普遍使用的Aki-Richards和Shuey近似,以Zoeppritz方程的准确解为参照,针对几种典型油藏反射界面,计算了Aki-Richards和Shuey近似所产生的相对误差,绘出了相对误差随入射角的变化曲线.计算表明,在存在极性反转的反射界面,Aki-Richards和Shuey近似的计算结果会带来很大的误差,在极性反转点附近的计算结果失去它的可信性;在泥岩与气砂、油砂或水砂组成的反射界面,即便就是在小角度范围内也存在较大的计算误差(如泥岩—气砂反射界,入射角在5°之内,相对误差就超过了10%);在油砂和水砂反射界面Aki Richards和Shuey是很好的近似.本文对Aki-Richards和Shuey近似结合几种典型油藏反射界面给出定量的分析,为储层参数反演方案的设计特别是反演道集及范围的选择提供理论依据.
