Seismic wave reflection method is an advanced geophysical detection method in tunnel geological prediction.It is more sensitive and effective in detecting geological anomalies such as fault fracture zone and karst.In ...Seismic wave reflection method is an advanced geophysical detection method in tunnel geological prediction.It is more sensitive and effective in detecting geological anomalies such as fault fracture zone and karst.In order to verify the prediction efficacy and accuracy of the seismic wave reflection method with different instruments and equipment(tunnel geological prediction[TGP]/tunnel seismic prediction[TSP])and different vibration modes(hammering,explosives),a comparison test was carried out in Jinping Tunnel.The test results showed that the time-consumption of the hammering source was short,which can greatly reduce the impact on the construction site;different vibration sources methods of seismic wave reflection can predict the unfavorable geological sections accurately.展开更多
Through solving the Zoeppritz's partial derivative equations, we have obtained accurate partial derivatives of reflected coefficients of seismic wave with respect to Pand S-wave velocities.With those partial deriv...Through solving the Zoeppritz's partial derivative equations, we have obtained accurate partial derivatives of reflected coefficients of seismic wave with respect to Pand S-wave velocities.With those partial derivatives, a multi-angle inversion is developed for seismic wave velocities.Numerical examples of different formation models show that if the number of iterations goes over 10, the relative error of inversion results is less than 1%, whether or not there is interference among the reflection waves.When we only have the reflected seismograms of P-wave, and only invert for velocities of P-wave, the multi-angle inversion is able to obtain a high computation precision.When we have the reflected seismograms of both P-wave and VS-wave, and simultaneously invert for the velocities of P-wave and VS-wave, the computation precisions of VS-wave velocities improves gradually with the increase of the number of angles, but the computation precision of P-wave velocities becomes worse.No matter whether the reflected seismic waves from the different reflection interface are coherent or non-coherent, this method is able to achieve a higher computation precision.Because it is based on the accurate solution of the gradient of SWRCs without any additional restriction, the multi-angle inversion method can be applied to seismic inversion of total angles.By removing the difficulties caused by simplified Zoeppritz formulas that the conventional AVO technology struggles with, the multiangle inversion method extended the application range of AVO technology and improved the computation precision and speed of inversion of seismic wave velocities.展开更多
We carried out surveying on the shallow structure and faulted-stratum of the Haihe fault in Tianjin using acoustic surveying methods such as the single-channel seismic technique. The result shows that the method can o...We carried out surveying on the shallow structure and faulted-stratum of the Haihe fault in Tianjin using acoustic surveying methods such as the single-channel seismic technique. The result shows that the method can obtain satisfactory results in wide and deep river courses. It also shows that in the Tanggu area of Tianjin, the upper fault point of Haihe fault is about 30m beneath the river bed and the corresponding latest active period is Qp^3- Qh^1 , which is consistent with the former borehole survey result. In the offshore area of the Bohai Sea, Haihe fault shows as a NWW-NEE strike dense fault zone and its upper fault point is less than 30m beneath the seabed. It shows that the active characteristics of Haihe fault in the Bohai Sea correspond to the Tanggu area.展开更多
文摘Seismic wave reflection method is an advanced geophysical detection method in tunnel geological prediction.It is more sensitive and effective in detecting geological anomalies such as fault fracture zone and karst.In order to verify the prediction efficacy and accuracy of the seismic wave reflection method with different instruments and equipment(tunnel geological prediction[TGP]/tunnel seismic prediction[TSP])and different vibration modes(hammering,explosives),a comparison test was carried out in Jinping Tunnel.The test results showed that the time-consumption of the hammering source was short,which can greatly reduce the impact on the construction site;different vibration sources methods of seismic wave reflection can predict the unfavorable geological sections accurately.
基金supported by Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality(PHR(IHLB))(Grant No.PHR201107145)
文摘Through solving the Zoeppritz's partial derivative equations, we have obtained accurate partial derivatives of reflected coefficients of seismic wave with respect to Pand S-wave velocities.With those partial derivatives, a multi-angle inversion is developed for seismic wave velocities.Numerical examples of different formation models show that if the number of iterations goes over 10, the relative error of inversion results is less than 1%, whether or not there is interference among the reflection waves.When we only have the reflected seismograms of P-wave, and only invert for velocities of P-wave, the multi-angle inversion is able to obtain a high computation precision.When we have the reflected seismograms of both P-wave and VS-wave, and simultaneously invert for the velocities of P-wave and VS-wave, the computation precisions of VS-wave velocities improves gradually with the increase of the number of angles, but the computation precision of P-wave velocities becomes worse.No matter whether the reflected seismic waves from the different reflection interface are coherent or non-coherent, this method is able to achieve a higher computation precision.Because it is based on the accurate solution of the gradient of SWRCs without any additional restriction, the multi-angle inversion method can be applied to seismic inversion of total angles.By removing the difficulties caused by simplified Zoeppritz formulas that the conventional AVO technology struggles with, the multiangle inversion method extended the application range of AVO technology and improved the computation precision and speed of inversion of seismic wave velocities.
基金the China Digital Seismic Observation Network Program and the Active Fault Detecting Sub-program of the tenth"Five-Year Plan" of China Earthquake Administration
文摘We carried out surveying on the shallow structure and faulted-stratum of the Haihe fault in Tianjin using acoustic surveying methods such as the single-channel seismic technique. The result shows that the method can obtain satisfactory results in wide and deep river courses. It also shows that in the Tanggu area of Tianjin, the upper fault point of Haihe fault is about 30m beneath the river bed and the corresponding latest active period is Qp^3- Qh^1 , which is consistent with the former borehole survey result. In the offshore area of the Bohai Sea, Haihe fault shows as a NWW-NEE strike dense fault zone and its upper fault point is less than 30m beneath the seabed. It shows that the active characteristics of Haihe fault in the Bohai Sea correspond to the Tanggu area.
