Liang Wang, H. Li, Donghui Wang, Sheng Zhou, Wei Zhang, Long Xia, Jian Yang, Qiao Wang
Understanding the shallow geological structure of urban areas is crucial for effective planning and development of underground spaces. Geophysical methods that are well-suited for site-specific investigation and have robustly anti-interference capabilities can provide important geological information for urban areas. In support of investigating the 3D geological structure of the shallow subsurface in Chengdu International Bio-City, a geophysical exploration study was conducted using three methods: the electrical resistivity tomography (ERT), micro-seismic exploration, and opposing-coil transient electromagnetic method (OCTEM). Results from the study showed that the ERT method was greatly affected by local high-resistance bodies, construction sites, and industrial currents, therefore leading to poor detection results that did not match well with the area's layered structure characteristics. The micro-seismic exploration method showed good layering effects and correlation with the drilling data in the elevation range of approximately 350 m to 436 m, but poor layering effects and low correlation with drilling data in the elevation range of about 235 m to 350 m, with relatively slow construction efficiency. The OCTEM showed good correlation with the drilling data for shallow depths up to 200 m and good identification capabilities for gypsum and mudstone in the area. Additionally, the instrument's anti-interference ability was suitable for complex urban conditions. Thus, OCTEM was selected for the area-based exploration with a 100 m × 10 m grid, rapidly obtaining 3D resistivity information for depths up to 200 m in the study area. By integrating the 3D resistivity information with known engineering geological information, a comprehensive three-dimensional geological model of the study area was created.
{"title":"Urban geophysical exploration: case study in Chengdu International Bio-City","authors":"Liang Wang, H. Li, Donghui Wang, Sheng Zhou, Wei Zhang, Long Xia, Jian Yang, Qiao Wang","doi":"10.1093/jge/gxad049","DOIUrl":"https://doi.org/10.1093/jge/gxad049","url":null,"abstract":"\u0000 Understanding the shallow geological structure of urban areas is crucial for effective planning and development of underground spaces. Geophysical methods that are well-suited for site-specific investigation and have robustly anti-interference capabilities can provide important geological information for urban areas. In support of investigating the 3D geological structure of the shallow subsurface in Chengdu International Bio-City, a geophysical exploration study was conducted using three methods: the electrical resistivity tomography (ERT), micro-seismic exploration, and opposing-coil transient electromagnetic method (OCTEM). Results from the study showed that the ERT method was greatly affected by local high-resistance bodies, construction sites, and industrial currents, therefore leading to poor detection results that did not match well with the area's layered structure characteristics. The micro-seismic exploration method showed good layering effects and correlation with the drilling data in the elevation range of approximately 350 m to 436 m, but poor layering effects and low correlation with drilling data in the elevation range of about 235 m to 350 m, with relatively slow construction efficiency. The OCTEM showed good correlation with the drilling data for shallow depths up to 200 m and good identification capabilities for gypsum and mudstone in the area. Additionally, the instrument's anti-interference ability was suitable for complex urban conditions. Thus, OCTEM was selected for the area-based exploration with a 100 m × 10 m grid, rapidly obtaining 3D resistivity information for depths up to 200 m in the study area. By integrating the 3D resistivity information with known engineering geological information, a comprehensive three-dimensional geological model of the study area was created.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43308668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The broadband finite-difference (FD) coefficients computed by a cost function have been widely applied to suppress of numerical dispersion. Under the same condition, the FD coefficients with small low-wavenumber dispersion error will produce a more accurate numerical solution in the long-time seismic wave simulation. Thus, how to reduce the low-wavenumber dispersion error becomes a crucial problem. According to the research of zero point position at the dispersion curve for three types of cost functions, we found that the more zero points concentrate on the low-wavenumber region, the less dispersion error. Therefore, the concentration of zero points is a good way to reduce dispersion error, which can be implemented by modified wavenumbers of zero points. Then, we design a Lagrange dual problem with a restriction based on the modified wavenumbers. The Requirements for constructing the Lagrange dual problem are the optimization function and restricted condition, where the former is based on the dispersion relation, and the latter comprises the modified wavenumbers. The solution of this optimization problem, calculated by the dual ascent method, affords a less low-wavenumber dispersion error than the solution yielded by the alternating direction method of multipliers (ADMM). The theoretical analysis and numerical modeling suggest that the proposed method is superior to the existing optimal FD coefficients in reducing numerical error accumulation in low-frequency simulation.
{"title":"Reducing the low-wavenumber dispersion error by building the Lagrange dual problem with a powerful local restriction","authors":"Peng Wei-ting, Jianping Huang, Yi Shen","doi":"10.1093/jge/gxad047","DOIUrl":"https://doi.org/10.1093/jge/gxad047","url":null,"abstract":"\u0000 The broadband finite-difference (FD) coefficients computed by a cost function have been widely applied to suppress of numerical dispersion. Under the same condition, the FD coefficients with small low-wavenumber dispersion error will produce a more accurate numerical solution in the long-time seismic wave simulation. Thus, how to reduce the low-wavenumber dispersion error becomes a crucial problem. According to the research of zero point position at the dispersion curve for three types of cost functions, we found that the more zero points concentrate on the low-wavenumber region, the less dispersion error. Therefore, the concentration of zero points is a good way to reduce dispersion error, which can be implemented by modified wavenumbers of zero points. Then, we design a Lagrange dual problem with a restriction based on the modified wavenumbers. The Requirements for constructing the Lagrange dual problem are the optimization function and restricted condition, where the former is based on the dispersion relation, and the latter comprises the modified wavenumbers. The solution of this optimization problem, calculated by the dual ascent method, affords a less low-wavenumber dispersion error than the solution yielded by the alternating direction method of multipliers (ADMM). The theoretical analysis and numerical modeling suggest that the proposed method is superior to the existing optimal FD coefficients in reducing numerical error accumulation in low-frequency simulation.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41978762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To improve the resolution of electromagnetic inversion for thin layers, electromagnetic one-dimensional inversion was studied. The smooth conductivity model produced by Occam's inversion cannot accurately represent the information of the subterranean thin resistive layers, leading to erroneous inversion findings. The existing thin resistive layers’ inversion method sets the model constraint term at the thin resistive layers to 0, resulting in abrupt changes in resistivity values. Given the above problems, we proposed an adaptive roughness matrix calculation method to improve the thin, lowly resistive-layer resolution. The resistivity difference between neighboring layers of the updated inversion model determines the roughness matrix, allowing for the realization of adaptive inversion of the thin layer. It achieves semi-airborne transient electromagnetic enhanced adaptive thin-layer inversion and automatically manages the model constraint term. The calculation of the synthetic model demonstrates that the improved adaptive thin-layer inversion method does not need to know the thin, lowly resistive layers information in advance. The model can produce appropriate inversion results regardless of the presence of thin, lowly-resistive layers. Finally, the drilling results are consistent with the inversed appearance of the semi-airborne transient electromagnetic field data. Other geophysical adaptive thin resistive layers inversion can also benefit from this research's findings.
{"title":"Improved adaptive thin-layer inversion for semi-airborne transient electromagnetic","authors":"Yougong Xian, Riyan Lan, Yuchao Liu, Dunren Li, Jing Yang, Huaifeng Sun","doi":"10.1093/jge/gxad045","DOIUrl":"https://doi.org/10.1093/jge/gxad045","url":null,"abstract":"\u0000 To improve the resolution of electromagnetic inversion for thin layers, electromagnetic one-dimensional inversion was studied. The smooth conductivity model produced by Occam's inversion cannot accurately represent the information of the subterranean thin resistive layers, leading to erroneous inversion findings. The existing thin resistive layers’ inversion method sets the model constraint term at the thin resistive layers to 0, resulting in abrupt changes in resistivity values. Given the above problems, we proposed an adaptive roughness matrix calculation method to improve the thin, lowly resistive-layer resolution. The resistivity difference between neighboring layers of the updated inversion model determines the roughness matrix, allowing for the realization of adaptive inversion of the thin layer. It achieves semi-airborne transient electromagnetic enhanced adaptive thin-layer inversion and automatically manages the model constraint term. The calculation of the synthetic model demonstrates that the improved adaptive thin-layer inversion method does not need to know the thin, lowly resistive layers information in advance. The model can produce appropriate inversion results regardless of the presence of thin, lowly-resistive layers. Finally, the drilling results are consistent with the inversed appearance of the semi-airborne transient electromagnetic field data. Other geophysical adaptive thin resistive layers inversion can also benefit from this research's findings.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61718825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Traditional tomographic methods do not consider the uncertainties associated with near-surface velocities and static corrections and provide a deterministic solution to the estimation problem. However, these uncertainties significantly impact structural mapping and interpretation of seismic imaging results. On the other hand, Bayesian first-arrival tomography provides multiple near-surface models that fit observed traveltimes equally well and enable the study of potential solution distributions. We demonstrate this approach on a complex synthetic near-surface model, representative of arid environments, to quantify associated velocity and statics uncertainties. We evaluate two different parameterizations for subsurface velocities in the context of near-surface Bayesian tomography: Voronoi tessellation with natural neighbor interpolation and the more conventional Delaunay triangulation with linear interpolation. Our analysis shows that the Voronoi cell parameterization with natural neighbor interpolation is more appropriate for this problem. Finally, the new approach is applied to compare two alternative acquisition geometries comprising conventional surface receivers and surface receivers augmented with vertical receiver arrays. The results demonstrate that adding vertical receiver arrays to conventional surface receivers can significantly reduce the near-surface velocity uncertainty and thus increases the accuracy of the seismic imaging results. Furthermore, the study shows that Bayesian tomography can be used as a tool for evaluating different source and receiver geometries during the acquisition design stage.
{"title":"Evaluating imaging uncertainty associated with the near surface and added value of vertical arrays using Bayesian seismic refraction tomography","authors":"I. Silvestrov, A. Egorov, A. Bakulin","doi":"10.1093/jge/gxad044","DOIUrl":"https://doi.org/10.1093/jge/gxad044","url":null,"abstract":"\u0000 Traditional tomographic methods do not consider the uncertainties associated with near-surface velocities and static corrections and provide a deterministic solution to the estimation problem. However, these uncertainties significantly impact structural mapping and interpretation of seismic imaging results. On the other hand, Bayesian first-arrival tomography provides multiple near-surface models that fit observed traveltimes equally well and enable the study of potential solution distributions. We demonstrate this approach on a complex synthetic near-surface model, representative of arid environments, to quantify associated velocity and statics uncertainties. We evaluate two different parameterizations for subsurface velocities in the context of near-surface Bayesian tomography: Voronoi tessellation with natural neighbor interpolation and the more conventional Delaunay triangulation with linear interpolation. Our analysis shows that the Voronoi cell parameterization with natural neighbor interpolation is more appropriate for this problem. Finally, the new approach is applied to compare two alternative acquisition geometries comprising conventional surface receivers and surface receivers augmented with vertical receiver arrays. The results demonstrate that adding vertical receiver arrays to conventional surface receivers can significantly reduce the near-surface velocity uncertainty and thus increases the accuracy of the seismic imaging results. Furthermore, the study shows that Bayesian tomography can be used as a tool for evaluating different source and receiver geometries during the acquisition design stage.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46769254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recovering anomalous information covered under noise in late gates can enhance airborne transient electromagnetic (ATEM) detection. Conventional denoising mainly comprises filtering and gate correlation-based decomposition algorithms; the former fails to extract anomalies contaminated by noise and the latter relies on the correlation between gates, which may yield false late gate anomalies caused by early large-amplitude anomalies in early gates. In ATEM profiles, the correlation between anomalies in adjacent gates makes the anomalies to be measured to have low-rank characteristics relative to the noise-contaminated profiles; the noise is uniformly distributed in the profiles, which have nonlocal self-similarity. Therefore, the low-rank matrix approximation algorithm is applicable to ATEM data denoising. In this study, an algorithm—noise-whitening-based weighted nuclear norm minimization (NW-WNNM)—is designed to remove ATEM profile noise. First, we analyse the influence of patch size in block matching on anomalous and noisy patches and estimate the profile patch size adaptively. Then, we combine the estimation of noise variance in weighted nuclear norm minimization (WNNM) with the noise whitening of similar patch matrices to reduce the noise interference on the nuclear norm and add a whitening factor in the weight vector to make the soft-thresholding function applicable to the low-rank reconstruction of the whitened matrix. By analysing the reconstructed low-rank matrix and its feature distribution, compared with WNNM, NW-WNNM can detect the feature information more accurately and eliminate the influence of noise on the nuclear norm. Simulation and field profile results indicate that NW-WNNM is superior to comparison denoising methods.
{"title":"Denoising for airborne transient electromagnetic data using noise-whitening-based weighted nuclear norm minimization","authors":"Cong Peng, K. Zhu, Tianjiao Fan, Yang Yang","doi":"10.1093/jge/gxad043","DOIUrl":"https://doi.org/10.1093/jge/gxad043","url":null,"abstract":"\u0000 Recovering anomalous information covered under noise in late gates can enhance airborne transient electromagnetic (ATEM) detection. Conventional denoising mainly comprises filtering and gate correlation-based decomposition algorithms; the former fails to extract anomalies contaminated by noise and the latter relies on the correlation between gates, which may yield false late gate anomalies caused by early large-amplitude anomalies in early gates. In ATEM profiles, the correlation between anomalies in adjacent gates makes the anomalies to be measured to have low-rank characteristics relative to the noise-contaminated profiles; the noise is uniformly distributed in the profiles, which have nonlocal self-similarity. Therefore, the low-rank matrix approximation algorithm is applicable to ATEM data denoising. In this study, an algorithm—noise-whitening-based weighted nuclear norm minimization (NW-WNNM)—is designed to remove ATEM profile noise. First, we analyse the influence of patch size in block matching on anomalous and noisy patches and estimate the profile patch size adaptively. Then, we combine the estimation of noise variance in weighted nuclear norm minimization (WNNM) with the noise whitening of similar patch matrices to reduce the noise interference on the nuclear norm and add a whitening factor in the weight vector to make the soft-thresholding function applicable to the low-rank reconstruction of the whitened matrix. By analysing the reconstructed low-rank matrix and its feature distribution, compared with WNNM, NW-WNNM can detect the feature information more accurately and eliminate the influence of noise on the nuclear norm. Simulation and field profile results indicate that NW-WNNM is superior to comparison denoising methods.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45795868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Shirzad, Nastaran Shakeri, M. K. Kakhki, S. Norouzi, I. Abdollahiefard
Local P-wave tomography is an efficient method to study geologically complex areas where the seismic exploration methods are not ideal for unraveling the shallow crustal heterogeneity due to the great thickness of evaporitic deposits. Despite the complex geological features in the salt-rich DehDasht region, SW Iran, we used >11 000 micro-earthquake events, which have been recorded by a temporary seismic network (deployed between 18 October 2016 and 1 July 2017), to derive the three-dimensional velocity structure based on the first arrival time. We selected a subset of events (1571 micro-earthquakes) by various strict criteria for our processing, and then the 1D velocity model was calculated by the computer program VELEST. Afterward, the 3D initial model of the inversion procedure with 1.5-km horizontal and 1-km deep intervals was parametrized using the calculated 1D model. Finally, the observed data (first arrival P-wave traveltimes and events locations) was inverted with an optimum regularization parameter and iteration using the computer program SIMULPS14. Our tomographic results indicate the DehDasht Basin as a relatively low-velocity zone filled out dominantly by the Gachsaran Formation and surrounded by the high-velocity Asmari-Pabdeh-Sarvak Formations. The basin has a bowl shape that is elongated in the NW–SE direction or an oval on a horizontal view. The depth of the basin varies between 3 and 5 km and contains many folding-faulting systems, which lead to locally low-velocity patches. Moreover, some evaporate deposits, which are overlying the Gachsaran Formation, emerge as a thin low-velocity layer (e.g. Aghajari, etc.).
{"title":"Three-dimensional P-wave model of the shallow crustal structure, a complementary method for detecting a trapped hydrocarbon: a case study in the DehDasht region, SW Iran","authors":"T. Shirzad, Nastaran Shakeri, M. K. Kakhki, S. Norouzi, I. Abdollahiefard","doi":"10.1093/jge/gxad031","DOIUrl":"https://doi.org/10.1093/jge/gxad031","url":null,"abstract":"\u0000 Local P-wave tomography is an efficient method to study geologically complex areas where the seismic exploration methods are not ideal for unraveling the shallow crustal heterogeneity due to the great thickness of evaporitic deposits. Despite the complex geological features in the salt-rich DehDasht region, SW Iran, we used >11 000 micro-earthquake events, which have been recorded by a temporary seismic network (deployed between 18 October 2016 and 1 July 2017), to derive the three-dimensional velocity structure based on the first arrival time. We selected a subset of events (1571 micro-earthquakes) by various strict criteria for our processing, and then the 1D velocity model was calculated by the computer program VELEST. Afterward, the 3D initial model of the inversion procedure with 1.5-km horizontal and 1-km deep intervals was parametrized using the calculated 1D model. Finally, the observed data (first arrival P-wave traveltimes and events locations) was inverted with an optimum regularization parameter and iteration using the computer program SIMULPS14. Our tomographic results indicate the DehDasht Basin as a relatively low-velocity zone filled out dominantly by the Gachsaran Formation and surrounded by the high-velocity Asmari-Pabdeh-Sarvak Formations. The basin has a bowl shape that is elongated in the NW–SE direction or an oval on a horizontal view. The depth of the basin varies between 3 and 5 km and contains many folding-faulting systems, which lead to locally low-velocity patches. Moreover, some evaporate deposits, which are overlying the Gachsaran Formation, emerge as a thin low-velocity layer (e.g. Aghajari, etc.).","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61718771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chuan Li, Minmin Li, Xiumei Yang, Weiping Zhang, Mingkun Fan, Xi Yang, Lu Wang
Relatively low ground-penetrating radar antenna frequencies are usually selected for tunnel inspection due to the thickness of the lining, which causes the geometric features of voids in the image to be blurred and difficult to identify. Therefore, the boundary points of the voids are determined by combining reflection and attenuation coefficients, and the geometric features are constructed to identify the voids. Depending on the electromagnetic differences between the void and other mediums in the lining, when the electromagnetic wave propagates from the lining concrete to the void, the reflection coefficient is positive, and the phase of the reflected wave is the same as the incident wave. Conversely, the phase of the reflected wave is opposite to the incident wave. Therefore, the boundary point can be determined in the one dimension time-waveform diagram (A-Scan) based on the phase change. Moreover, the amplitude of the electromagnetic wave attenuates exponentially in the concrete, but it attenuates slowly in the void. And electromagnetic waves exhibit high-frequency characteristics in the lining but low-frequency characteristics in the voids. Boundary points that conform to the variation of amplitude and frequency characteristics in the void are screened. These boundary points are then constructed in two-dimensional scan data (B-Scan) to identify the voids by using the geometry of the voids. This method is applied to the Hu Sa tunnel. The voids are successfully identified in the mileage section YK81+310 - YK81+422 of the Hu Sa tunnel, and the depth of cover and the area of voids are correctly estimated.
{"title":"Boundary recognition of tunnel lining void from ground penetrating radar data","authors":"Chuan Li, Minmin Li, Xiumei Yang, Weiping Zhang, Mingkun Fan, Xi Yang, Lu Wang","doi":"10.1093/jge/gxad041","DOIUrl":"https://doi.org/10.1093/jge/gxad041","url":null,"abstract":"\u0000 Relatively low ground-penetrating radar antenna frequencies are usually selected for tunnel inspection due to the thickness of the lining, which causes the geometric features of voids in the image to be blurred and difficult to identify. Therefore, the boundary points of the voids are determined by combining reflection and attenuation coefficients, and the geometric features are constructed to identify the voids. Depending on the electromagnetic differences between the void and other mediums in the lining, when the electromagnetic wave propagates from the lining concrete to the void, the reflection coefficient is positive, and the phase of the reflected wave is the same as the incident wave. Conversely, the phase of the reflected wave is opposite to the incident wave. Therefore, the boundary point can be determined in the one dimension time-waveform diagram (A-Scan) based on the phase change. Moreover, the amplitude of the electromagnetic wave attenuates exponentially in the concrete, but it attenuates slowly in the void. And electromagnetic waves exhibit high-frequency characteristics in the lining but low-frequency characteristics in the voids. Boundary points that conform to the variation of amplitude and frequency characteristics in the void are screened. These boundary points are then constructed in two-dimensional scan data (B-Scan) to identify the voids by using the geometry of the voids. This method is applied to the Hu Sa tunnel. The voids are successfully identified in the mileage section YK81+310 - YK81+422 of the Hu Sa tunnel, and the depth of cover and the area of voids are correctly estimated.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42041728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anisotropic pseudo-acoustic forward modeling and migration imaging are critical for high-precision seismic exploration. However, the wavefields simulated by the traditional coupled anisotropic acoustic wave equation have the problems of shear wave noise and numerical simulation instability for epsilon that is less than delta. Furthermore, although the pure anisotropic acoustic wave equation expressed by the differential operators can solve the aforementioned noise interference and numerical simulation instability issues, its numerical simulation calculation is large, particularly in 3D industrial applications, because it has to be solved by the spectral-based method. In this paper, a pure anisotropic acoustic wave equation in a vertical transverse isotropic (VTI) medium that can be numerically computed using the efficient finite difference method is derived. This equation not only eliminates noise interference and numerical simulation instabilities, but also allows for efficient wavefield simulation. We also implement reverse time migration (RTM) using the proposed VTI pure anisotropic acoustic wave equation. Two synthetic tests and one field data test are performed to evaluate the accuracy and robustness of the developed VTI RTM. The imaging results show that the proposed VTI RTM can correct the anisotropy effect on seismic wave propagation and improve migration imaging precision.
{"title":"Efficient pure qP-wave simulation and reverse time migration imaging for vertical transverse isotropic (VTI) media","authors":"X. Mu, Jianping Huang, Q. Mao, Jiale Han","doi":"10.1093/jge/gxad039","DOIUrl":"https://doi.org/10.1093/jge/gxad039","url":null,"abstract":"\u0000 Anisotropic pseudo-acoustic forward modeling and migration imaging are critical for high-precision seismic exploration. However, the wavefields simulated by the traditional coupled anisotropic acoustic wave equation have the problems of shear wave noise and numerical simulation instability for epsilon that is less than delta. Furthermore, although the pure anisotropic acoustic wave equation expressed by the differential operators can solve the aforementioned noise interference and numerical simulation instability issues, its numerical simulation calculation is large, particularly in 3D industrial applications, because it has to be solved by the spectral-based method. In this paper, a pure anisotropic acoustic wave equation in a vertical transverse isotropic (VTI) medium that can be numerically computed using the efficient finite difference method is derived. This equation not only eliminates noise interference and numerical simulation instabilities, but also allows for efficient wavefield simulation. We also implement reverse time migration (RTM) using the proposed VTI pure anisotropic acoustic wave equation. Two synthetic tests and one field data test are performed to evaluate the accuracy and robustness of the developed VTI RTM. The imaging results show that the proposed VTI RTM can correct the anisotropy effect on seismic wave propagation and improve migration imaging precision.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46923448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An accurate assessment of the stress concentration of the surrounding rock is crucial for ensuring safety in underground coal mines with a high potential for rockburst accidents. Traditional methods for measuring the stress of the surrounding rock use borehole stress monitoring equipment and drilling and cutting methods. However, these methods do not always yield accurate and reliable data. In this study, we aim to explore the feasibility of a novel approach for characterizing stress concentration in surrounding rock using monitoring while drilling (MWD) technology during large-diameter drilling. This study combined microseismic monitoring to collect vibration signals during the drilling process and collection of pulverized coal samples at each drilling stage. We analyzed the amplitude, number of coal vibration events and proportion of coarse pulverized coal. By integrating these indices, we characterized the stress concentration in the surrounding rock. Our approach was validated by comparing accurate, stable, and representative data from deep- and shallow-hole stress gauges installed in similar locations and data from the conventional drilling cutting method. Our findings indicate that the proposed method provides a reliable and effective alternative to traditional techniques during large-diameter drilling. The proposed approach can significantly enhance safety management in underground coal mines prone to rockburst accidents.
{"title":"A new method for characterization of stress concentration degree of coal mine roadway surrounding rock","authors":"Kai Zhan, Xiaotao Wen, Xuben Wang, C.M. Kong","doi":"10.1093/jge/gxad040","DOIUrl":"https://doi.org/10.1093/jge/gxad040","url":null,"abstract":"\u0000 An accurate assessment of the stress concentration of the surrounding rock is crucial for ensuring safety in underground coal mines with a high potential for rockburst accidents. Traditional methods for measuring the stress of the surrounding rock use borehole stress monitoring equipment and drilling and cutting methods. However, these methods do not always yield accurate and reliable data. In this study, we aim to explore the feasibility of a novel approach for characterizing stress concentration in surrounding rock using monitoring while drilling (MWD) technology during large-diameter drilling. This study combined microseismic monitoring to collect vibration signals during the drilling process and collection of pulverized coal samples at each drilling stage. We analyzed the amplitude, number of coal vibration events and proportion of coarse pulverized coal. By integrating these indices, we characterized the stress concentration in the surrounding rock. Our approach was validated by comparing accurate, stable, and representative data from deep- and shallow-hole stress gauges installed in similar locations and data from the conventional drilling cutting method. Our findings indicate that the proposed method provides a reliable and effective alternative to traditional techniques during large-diameter drilling. The proposed approach can significantly enhance safety management in underground coal mines prone to rockburst accidents.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45243466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In seismic exploration, a precise description of the seismic reflection property is critical for reservoir prediction and fluid identification. In the study of seismic wave transmission effects, taking into account both the viscoelastic and anisotropic properties of a medium is compatible with the features of the earth. Moreover, it is advantageous to the characterization of complicated reservoirs. According to the elastic medium foundation and the imaginary component with quality factor Q, seismic reflection properties of viscoelastic media are described in the complex domain. The complex wave number is expressed by phase velocity and Q. The attenuation angle is introduced when the complex wave number is represented by a propagation vector and an attenuation vector. The exact velocity and polarization direction of a viscoelastic medium are expressed using a complex stiffness matrix incorporating Q matrix elements. The quasi-Zoeppritz equation for viscoelastic horizontal transverse isotropic (VHTI) media is derived by using boundary conditions based on the wave function of viscoelastic media. The numerical simulation of reflectivity reveals that the reflection coefficient in a viscoelastic medium is clearly different from that of an elastic medium. Moreover, the difference in reflection coefficient in various orientations has distinct characteristics.
{"title":"Azimuthal seismic reflection characteristics with quality factor Q in viscoelastic horizontal transverse isotropic media","authors":"Yijun Xi, Xingyao Yin","doi":"10.1093/jge/gxad038","DOIUrl":"https://doi.org/10.1093/jge/gxad038","url":null,"abstract":"\u0000 In seismic exploration, a precise description of the seismic reflection property is critical for reservoir prediction and fluid identification. In the study of seismic wave transmission effects, taking into account both the viscoelastic and anisotropic properties of a medium is compatible with the features of the earth. Moreover, it is advantageous to the characterization of complicated reservoirs. According to the elastic medium foundation and the imaginary component with quality factor Q, seismic reflection properties of viscoelastic media are described in the complex domain. The complex wave number is expressed by phase velocity and Q. The attenuation angle is introduced when the complex wave number is represented by a propagation vector and an attenuation vector. The exact velocity and polarization direction of a viscoelastic medium are expressed using a complex stiffness matrix incorporating Q matrix elements. The quasi-Zoeppritz equation for viscoelastic horizontal transverse isotropic (VHTI) media is derived by using boundary conditions based on the wave function of viscoelastic media. The numerical simulation of reflectivity reveals that the reflection coefficient in a viscoelastic medium is clearly different from that of an elastic medium. Moreover, the difference in reflection coefficient in various orientations has distinct characteristics.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44252763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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