Polarization Migration of Multi-component Seismic Data for Survey in the Tunnel of Mountain Cities

2019 ◽  
Vol 24 (4) ◽  
pp. 569-578
Author(s):  
Bo Wang ◽  
Lanying Huang ◽  
Shengdong Liu ◽  
Fubao Zhou ◽  
Biao Jin ◽  
...  
Keyword(s):  
Polarization Characteristic ◽  
Matrix Analysis ◽  
Seismic Exploration ◽  
Polarization Direction ◽  
Tunnel Face ◽  
Tunnel Detection ◽  
Migration Imaging ◽  
Seismic Detection ◽  
Migration Method ◽  
Principal Polarization

With the development of transportation in the west of China, tunnel construction in mountain cities is becoming very important and widespread. Tunneling safety in the tunnels is usually controlled by faults, and the advanced prediction of faults by seismic detection method has become a research hotspot in the field of engineering geophysics. Unlike seismic exploration on the ground, the sources and receivers are not properly arranged due to the limitation of the tunnel detection space, so as to cause migration artifacts problem in the process of advanced migration imaging. The problem results in inaccurate imaging of the faults. To solve the problem, this paper proposed a new polarization migration method. The method makes use of the polarization characteristic of three-component seismic signals. The principal polarization direction is calculated by Hilbert transform and complex covariance matrix analysis. A weighted function of the principal polarization direction factor is incorporated into the migration calculation. To verify the effectiveness of the polarization migration method, this paper carries out numerical simulations. Test results demonstrate that the artifacts are eliminated by the polarization migration, and occurrence parameters of faults, such as dip and trend are calculated accurately. The field detection case shows that seismic advanced prediction which is based on polarization migration provided parameters of faults in the front of the tunnel face with 100m, and the distance error is less than 2m, and the dip error is less than 3°, which ensures efficient and safe construction of tunneling.

An introduction to seismic exploration of the Micang-Dabashan foothill belt in the Sichuan Basin

2018 ◽  
Vol 6 (4) ◽  
pp. SM39-SM50
Author(s):  
Jingbo Wang ◽  
Zhongshan Qi ◽  
Penggui Jing ◽  
Tianfa Zheng ◽  
Yanqi Li ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Oil And Gas ◽  
Seismic Exploration ◽  
Small Scale ◽  
Marine Strata ◽  
Piedmont Zone ◽  
Migration Imaging ◽  
Imaging Results ◽  
Platform Margin ◽  
The Sichuan Basin

Geologic studies indicate that the platform-margin reef-shallow facies in Permo-Triassic marine strata in the Micang-Dabashan foothill belt in the Sichuan Basin are favorable exploration targets for oil and gas exploration. However, the typical dual-complexity problem (complex surface condition and subsurface structure) brings a great challenge for seismic technology targeting of those potential oil and gas reservoirs. To overcome this problem, varieties of advanced seismic acquisition and processing methods have been used to improve the imaging quality of piedmont seismic data since 2000. Some improvements have been achieved: The reflection waves from the far offset and deep layer can be acquired in shot gathers from limestone outcropped areas, and the signal-to-noise ratio (S/N) of reflection and diffraction waves in the stack section has been enhanced significantly so as to reveal amounts of valuable geologic information. The resolution and the S/N of seismic migration imaging for the strong fold zone in marine strata have been improved partially, so that the structure of the step-fault zone and the enveloping of gypsum rock are clearer than those revealed by the old seismic section. Even so, actual drilling data demonstrate that the subsurface structures of the foothill belt are far more complex than those revealed by the current seismic imaging results. Therefore, postdrilling evaluation for the validity of seismic techniques implemented in the Nanjiang and Zhenba piedmont zone has been carried out. The results indicate that the current acquisition scheme and processing workflow cannot completely fulfill the requirements of high-precision velocity modeling and migration imaging of complex structures (such as footwalls of thrust fault and small-scale fault blocks) in the piedmont zone, especially when the rugged surface and the widespread limestone outcrop appear simultaneously. Finally, we have developed some potential needs of seismic theories and techniques in the foothill belt, including seismic wave propagation, acquisition, and processing technology.

Imaging the Geology Ahead of a Tunnel Using Seismics and Adaptive Polarization Analysis

2020 ◽  
Vol 25 (2) ◽  
pp. 189-198
Author(s):  
Lei Chen ◽  
Chao Fu ◽  
Xinji Xu ◽  
Lichao Nie
Keyword(s):  
Time Window ◽  
Geophysical Methods ◽  
Weighting Coefficient ◽  
Tunnel Construction ◽  
Polarization Analysis ◽  
Polarization Direction ◽  
Tunnel Face ◽  
Seismic Method ◽  
Imaging Results ◽  
Geological Conditions

The seismic method is one of the main geophysical methods that are widely used to image the geology ahead of tunnels during tunnel construction. However, owing to the complex environment and limited observation aperture in a tunnel, symmetric false results (that appear in imaging results but not in the actual environment) frequently occur in imaging results. In a symmetric false reflection, false and true reflection points are axisymmetric around the tunnel axis. Such false results frequently cause errors in the interpretation of the geological conditions ahead of a tunnel face. To overcome this problem, a seismic method that uses adaptive polarization analysis was adopted to better image geological conditions. Based on an adaptive time window, the polarization characteristics of seismic signals were analyzed to calculate the main polarization direction. The symmetric false results in imaging results were suppressed by adopting a weighting coefficient based on the angle between the main polarization direction and ray direction. Numerical simulations revealed the superiority of the method when applied to synthetic data processing. Moreover, the method was applied to a diversion tunnel. The method successfully identified the fracture zones ahead of the tunnel face, thus significantly enhancing the safety of tunnel construction.

NOTES ON THE SESSION ON GOVERNMENT SCIENCE AT THE SEG CONVENTION IN GALVESTON, TEXAS, NOVEMBER 1960

Geophysics ◽  
1961 ◽  
Vol 26 (4) ◽  
pp. 508-513
Author(s):  
F. A. Van Melle
Keyword(s):  
World Wide ◽  
Seismic Station ◽  
Seismic Exploration ◽  
Seismic Control ◽  
System A ◽  
Seismic Detection ◽  
History Of ◽  
Nuclear Tests ◽  
Construction Operation ◽  
Dew Line

The history of the attempts at seismic control of nuclear tests shows that even before the discovery of decoupling or muffling—known in seismic exploration from shooting in a dry cavity—of explosions, the state of the art favored the cheating nation. With muffling, detection lags concealment of small nuclear tests by a factor in excess of one hundred. Technical and political considerations cannot be separated. A multibillion dollar effort such as the 180 seismic‐station Geneva system should not be undertaken without virtual certainty of adequate detection. If delays in construction, operation, and in situ inspection rendered the program ineffective within Russia and China after the free world had spent billions on the network in other parts of the world; the West would have suffered a sensitive cold war defeat and incurred the resentment of the underdeveloped nations. It would face frustration and loss of confidence at home. A fraction of the number of Geneva stations within the U.S.S.R., supplemented by a world‐wide net of seismological observatories of universities and other bodies with standard modern equipment and exchange of personnel and data, would have all the indirect advantages claimed by Dr. H. Bethe for the full Geneva system. A break‐through in research to advance detection by a factor in excess of one hundred is needed before an effort of DEW line magnitude appears justified. The probability of radical break‐throughs in research is never large. This diminishes the importance of attempts to improve detection by factors of two or three and of auxiliary development projects, such as those connected with on‐site inspection which presuppose effective seismic detection by a world‐wide net of stations.

Mapping water-abundant zones using transient electromagnetic and seismic methods when tunneling through fractured granite in the Qinling Mountains, China

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. B147-B159
Author(s):  
Bin Liu ◽  
Kerui Fan ◽  
Lichao Nie ◽  
Xiu Li ◽  
Fusheng Liu ◽  
...  
Keyword(s):  
Apparent Resistivity ◽  
Water Inrush ◽  
Cost Effective ◽  
Tunnel Face ◽  
Water Transportation ◽  
Transient Electromagnetic ◽  
Fractured Zones ◽  
Migration Imaging ◽  
Boundary Information ◽  
Fractured Granite

Severe water inrush currently halts the excavation of the Qinling Water Transportation Tunnel and has even stopped tunneling. Based on the geologic conditions of the construction area, the source of water inrush is abundant groundwater in fractured granite. To accurately predict water inrush, we must know the location, geometry, and boundary information of water-abundant zones before excavation. We have developed a field study of integrated seismic and transient electromagnetic (TEM) applications to map the water-abundant zones ahead of the tunnel face. Before the in-tunnel survey, numerical experiments based on excavation and drilling records verified the feasibility of our scheme. To reveal the fractured zones that may be filled with groundwater, an equitraveltime plane algorithm was used in the seismic data processing. Then, the TEM apparent resistivity was calculated to investigate the water-bearing condition of the fractured zones. To detect the water-abundant zone boundaries, we conducted migration imaging of the TEM pseudowavefield that was extracted from the measured TEM signals. A correlation stacking process to extract the TEM pseudowavefield was used to mitigate the ill-posed effect in the inverse wavefield transformation and obtain boundary information of the water-abundant zones. As expected, the results revealed the depth and geometry of the front and rear boundaries of two water-abundant zones 30 m ahead of the tunnel face, which is consistent with drilling and excavation records after the survey. The results of our case study indicate that the integration of seismic imaging, apparent resistivity imaging, and TEM pseudowavefield migration is an efficient and cost-effective method to provide the location, geometry, and boundary information of water-abundant zones.

scholarly journals Study on observation system of seismic forward prospecting in tunnel: A case on tailrace tunnel of Wudongde hydropower station

2022 ◽  
Vol 14 (1) ◽  
pp. 1-12
Author(s):  
Senlin Yang ◽  
Hongyi Cao ◽  
Yi Zhang ◽  
Lei Chen ◽  
Xinji Xu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Space Environment ◽  
Hydropower Station ◽  
Observation System ◽  
Tunnel Face ◽  
Field Environment ◽  
Single Side ◽  
Imaging Results ◽  
Seismic Detection ◽  
Tailrace Tunnel

Abstract Seismic method is a major approach for detecting the seismic geological features ahead of the tunnel, understanding the distribution of unfavorable geology, and ensuring the safety of tunnel construction. Observation system is the key for seismic detection, many studies have been conducted to optimize the observation system; however, most of them focused on the surface seismic investigation and numerical simulation rather than in tunnel field environment (limited aperture and full space environment). How to obtain better wavefield information with limited observation aperture is a great challenge. In this study numerical simulation and instrumental techniques (GPR, DC, etc.) were implemented to further check the result of seismic detection at the 1# tailrace tunnel at the Wudongde hydropower station. In the field case, observation detectors were arranged spatially in the tunnel and source points were placed in four ways: linearly along a single side, on the tunnel face, in front of the detectors, and behind the detectors. Then, after data acquisition, the data processing is conducted to carry out the migration results. The imaging results indicate that the observation system with sources and detectors in liner arrangement (with equal interval) helps to suppress artifacts, further supporting the advantages of spatial observation system with liner observation line (detectors). Moreover, the study provides suggestions for geological prospecting in similar tunnel projects.

Ground Penetrating Radar Imaging Based on FDTD Migration Method

2012 ◽  
Vol 490-495 ◽  
pp. 1261-1264 ◽  
Author(s):  
Yao Qin ◽  
Qi Fu Wang
Keyword(s):  
Time Domain ◽  
Ground Penetrating Radar ◽  
Finite Difference Time Domain ◽  
Computer Memory ◽  
Migration Imaging ◽  
Detection Technology ◽  
Simulation And Experiment ◽  
Migration Method ◽  
Ground Penetrating ◽  
Difference Time

Estimation the shape and position of the objects is an important subject in ground penetrating radar(GPR). Migration method is popular used in seismic wave detection technology to locate and reshape the objects. Finite difference time domain(FDTD) migration method is widely used not only because the iterative method can save the computer memory but also because it is sensitive with different horizontal velocity and vertical velocity of electromagnetic wave. In this paper, migration imaging principle is been introduced at first, then FDTD migration method is been discussed. By dealing with GPR simulation and experiment image, it shows that the FDTD Migration method used in GPR imaging is effectiveness and stability.

scholarly journals 3-D Multi-Component Reverse Time Migration Method for Tunnel Seismic Data

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3244
Author(s):  
Peng Guan ◽  
Cuifa Shao ◽  
Yuyong Jiao ◽  
Guohua Zhang ◽  
Bin Li ◽  
...  
Keyword(s):  
Seismic Data ◽  
Cross Correlation ◽  
Measured Data ◽  
Ray Theory ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Kirchhoff Migration ◽  
Time Migration ◽  
Migration Imaging ◽  
Migration Method

Migration imaging is a key step in tunnel seismic data processing. Due to the limitation of tunnel space, tunnel seismic data are small-quantity, multi-component, and have a small offset. Kirchhoff migration based on the ray theory is limited to the migration aperture and has low migration imaging accuracy. Kirchhoff migration can no longer meet the requirements of high-precision migration imaging. The reverse time migration (RTM) method is used to realize cross-correlation imaging by reverse-time recursion principle of the wave equation. The 3-D RTM method cannot only overcome the effect of small offset, but also realize multi-component data imaging, which is the most accurate migration method for tunnel seismic data. In this paper, we will study the 3-D RTM method for multi-component tunnel seismic data. Combined with the modeled data and the measured data, the imaging accuracy of the 3-D Kirchhoff migration and 3-D RTM is analyzed in detail. By comparing single-component and multi-component Kirchhoff migration and RTM profile, the advantages of the multi-component RTM method are summarized. Compared with the Kirchhoff migration method, the 3-D RTM method has the following advantages: (1) it can overcome the effect of small offset and expand the range of migration imaging; (2) multi-component data can be realized to improve the energy of anomalous interface; (3) it can make full use of multiple waves to realize migration imaging and improve the resolution of the anomalous interface. The modeled data and the measured data prove the advantages of the 3-D multi-component RTM method.

Decoupled elastic least-squares reverse time migration and its application in tunnel geological forward-prospecting

Geophysics ◽  
2021 ◽  
pp. 1-136
Author(s):  
Bin Liu ◽  
Jiansen Wang ◽  
Yuxiao Ren ◽  
Xu Guo ◽  
Lei Chen ◽  
...  
Keyword(s):  
Least Squares ◽  
Tunnel Construction ◽  
Stable Convergence ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Migration Imaging ◽  
Imaging Results ◽  
Geological Conditions ◽  
Migration Method

Accurate seismic imaging can ensure safe and efficient tunnel construction under complex geological conditions. As a high-precision migration method, reverse time migration (RTM) has been introduced into tunnel seismic forward-prospecting. However, the resolution of traditional RTM imaging results may not meet the requirements in a complex tunnel environment, which affects the interpretation of tunnel seismic forward-prospecting results. In this study, we propose a least-squares RTM method based on the decoupled elastic wave equation in tunnels. The Born forward modeling operator and its exact adjoint migration imaging operator are derived to ensure a stable convergence of the conjugate gradient method. Moreover, a pseudo-Hessian based preconditioning operator is adopted to accelerate the convergence. Numerical examples are provided to verify the efficiency of the proposed scheme. A field test in a traffic tunnel construction site is performed to show the good application effect of the decoupled elastic least-squares RTM in practical situations.

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