Pub Date : 2025-02-03DOI: 10.1016/j.jappgeo.2025.105643
Tao Jiang , Bohai Ke , Xiaobing Yu , Li Yu , Meng Yang , Ji Fan , Chenyuan Hu , Wei Feng , Huafeng Liu , Min Zhong , Liangcheng Tu , Zebing Zhou
Gravity gradient, defined as the spatial derivative of gravitational acceleration, represents the detailed variation of the gravity field and plays a significant role in resource exploration and auxiliary navigation. Airborne gravity gradient measurement is an important method for obtaining high-precision gravity gradient data. Compared to traditional gravity measurement techniques, it offers superior measurement efficiency and provides high-frequency information of gravity field which reveals small-scale terrain features. However, it also introduces more high-frequency measurement noise. Due to the randomness of Earth's topography and resource distribution, the high-frequency characteristics of gravity gradient signals are mainly concentrated in specific time and frequency ranges, exhibiting distinct time-frequency features. This paper employs the VMD and Hilbert transform to obtains the time-frequency features of gravity gradient signal, and proposes a time-frequency feature threshold method to extract gravity gradient signal. This method can accurately analyze and extract the gravity gradient signals components without being affected by the same frequency noise, suppressing 78 % of the noise in simulation data. Additionally, the proposed method is validated in the gravity gradient data of actual terrain, demonstrating over 19 % improvement compared to traditional smooth filter and wavelet threshold methods. Furthermore, it effectively retains the high-frequency characteristics of gravity gradient signal, enhancing the advantages of airborne gravity gradient signals
{"title":"Gravity gradient signal extraction based on time-frequency feature threshold method","authors":"Tao Jiang , Bohai Ke , Xiaobing Yu , Li Yu , Meng Yang , Ji Fan , Chenyuan Hu , Wei Feng , Huafeng Liu , Min Zhong , Liangcheng Tu , Zebing Zhou","doi":"10.1016/j.jappgeo.2025.105643","DOIUrl":"10.1016/j.jappgeo.2025.105643","url":null,"abstract":"<div><div>Gravity gradient, defined as the spatial derivative of gravitational acceleration, represents the detailed variation of the gravity field and plays a significant role in resource exploration and auxiliary navigation. Airborne gravity gradient measurement is an important method for obtaining high-precision gravity gradient data. Compared to traditional gravity measurement techniques, it offers superior measurement efficiency and provides high-frequency information of gravity field which reveals small-scale terrain features. However, it also introduces more high-frequency measurement noise. Due to the randomness of Earth's topography and resource distribution, the high-frequency characteristics of gravity gradient signals are mainly concentrated in specific time and frequency ranges, exhibiting distinct time-frequency features. This paper employs the VMD and Hilbert transform to obtains the time-frequency features of gravity gradient signal, and proposes a time-frequency feature threshold method to extract gravity gradient signal. This method can accurately analyze and extract the gravity gradient signals components without being affected by the same frequency noise, suppressing 78 % of the noise in simulation data. Additionally, the proposed method is validated in the gravity gradient data of actual terrain, demonstrating over 19 % improvement compared to traditional smooth filter and wavelet threshold methods. Furthermore, it effectively retains the high-frequency characteristics of gravity gradient signal, enhancing the advantages of airborne gravity gradient signals</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"234 ","pages":"Article 105643"},"PeriodicalIF":2.2,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349184","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2025.105632
Jianhui Hu , Liuyang Xu , Yaotian Yin , Xu Jia , Ping Qi , Zhan Liang , Peng Su , Cheng Liu , Weidong Tang , Long Chen , Yanzhou Wang , Lin Liu
This study utilized audio-frequency magnetotelluric (AMT) data collected from a concealed fluorite deposit on Huashitou Mountain in the Beishan metallogenic belt to obtain a 3-D resistivity model beneath the deposit. The fluorite ore-forming mechanism was determined and is discussed in combination with previous high-resolution magnetic and induced-polarization imaging results. Our study revealed a large high-resistivity body, R2 (> 1000 Ω·m), corresponding to the low induced-polarization and low-magnetic region that extends from 40 to > 80 m in depth. We suggest that this corresponds to the Indosinian intrusive granite, and potentially serves as a fluorite mineralization rock mass. A highly conductive zone, C3 (< 3 Ω·m), extending from approximately 20 to 300 m, or even deeper, was interpreted as a deep fault/fracture zone functioning as a fluid pathway for fluorite mineralization. Two smaller conductive zones, C1 and C2 (< 20 Ω·m), appear above the high-resistivity granite intrusion. These zones correspond well with high induced-polarization anomalies (> 2.5 % threshold), relatively high-△T anomalies (−50 nT), and hematite alteration areas shown on the geological cross-sections. These zones were interpreted as two near-surface secondary fault structures. The aforementioned fault structures are believed to have formed before the main mineralization period of the fluorite deposit and were subsequently reactivated during intense tectonic-magmatic activity in the Late Hercynian. Hot fluids enriched with volatile components (e.g., F and CO2) were transported along the deep fault, represented by C3, from the lower crust to the near-surface secondary fault zones (represented by C1 and C2). These fluids interacted with the calcic plagioclase in alkaline granite magma to form fluorite (mainly composing CaF2) through calcium extraction. Further, the process led to hydrothermal alteration, resulting in associated iron-oxide mineralization or silicification alteration zones, as well as alterations related to a sedimentary layer such as kaolinization and chloritization. These zones exhibit high conductivity because of their significant porosity and the presence of fluids or metal sulfides.
{"title":"Application of 3-D inversion of AMT data in exploration of concealed nonmetallic deposits: A Case Study on the Huashitou Mountain fluorite deposit in Beishan metallogenic belt, China","authors":"Jianhui Hu , Liuyang Xu , Yaotian Yin , Xu Jia , Ping Qi , Zhan Liang , Peng Su , Cheng Liu , Weidong Tang , Long Chen , Yanzhou Wang , Lin Liu","doi":"10.1016/j.jappgeo.2025.105632","DOIUrl":"10.1016/j.jappgeo.2025.105632","url":null,"abstract":"<div><div>This study utilized audio-frequency magnetotelluric (AMT) data collected from a concealed fluorite deposit on Huashitou Mountain in the Beishan metallogenic belt to obtain a 3-D resistivity model beneath the deposit. The fluorite ore-forming mechanism was determined and is discussed in combination with previous high-resolution magnetic and induced-polarization imaging results. Our study revealed a large high-resistivity body, R2 (> 1000 Ω·m), corresponding to the low induced-polarization and low-magnetic region that extends from 40 to > 80 m in depth. We suggest that this corresponds to the Indosinian intrusive granite, and potentially serves as a fluorite mineralization rock mass. A highly conductive zone, C3 (< 3 Ω·m), extending from approximately 20 to 300 m, or even deeper, was interpreted as a deep fault/fracture zone functioning as a fluid pathway for fluorite mineralization. Two smaller conductive zones, C1 and C2 (< 20 Ω·m), appear above the high-resistivity granite intrusion. These zones correspond well with high induced-polarization anomalies (> 2.5 % threshold), relatively high-△T anomalies (−50 nT), and hematite alteration areas shown on the geological cross-sections. These zones were interpreted as two near-surface secondary fault structures. The aforementioned fault structures are believed to have formed before the main mineralization period of the fluorite deposit and were subsequently reactivated during intense tectonic-magmatic activity in the Late Hercynian. Hot fluids enriched with volatile components (e.g., F and CO<sub>2</sub>) were transported along the deep fault, represented by C3, from the lower crust to the near-surface secondary fault zones (represented by C1 and C2). These fluids interacted with the calcic plagioclase in alkaline granite magma to form fluorite (mainly composing CaF<sub>2</sub>) through calcium extraction. Further, the process led to hydrothermal alteration, resulting in associated iron-oxide mineralization or silicification alteration zones, as well as alterations related to a sedimentary layer such as kaolinization and chloritization. These zones exhibit high conductivity because of their significant porosity and the presence of fluids or metal sulfides.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105632"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097096","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2025.105625
Tianyou Liu , Xiaoniu Zeng , Xihai Li , Longwei Chen , Jihao Liu , Xiaofeng Tan , Hongru Li
Gravity downward continuation is an effective method for processing and interpreting gravity data. Finding a gravity downward continuation method with high accuracy and stability is a persistent and popular research topic. At present, there are two common strategies for reducing the ill-posedness inherent in the downward continuation of potential fields, namely, regularization, and the design of wavenumber domain filtering operators. However, these downward continuation strategies often result in unsatisfactory continuation accuracy due to excessive smoothing of the downward continued field. To improve the stability and accuracy of the gravity downward continuation calculation, we construct an equivalent mathematical model of gravity downward continuation. This model is not only equivalent to the traditional gravity downward continuation model but also introduces nonnegative constraints into gravity downward continuation. This approach effectively reduces the ill-posedness of gravity downward continuation. Based on the newly proposed gravity downward continuation model, we propose a constrained gravity downward continuation method. Comparison experiments based on a synthetic gravity model and real gravity anomaly data show that, compared with the other four high performance unconstrained potential field downward continuation methods, the constrained downward continuation method proposed in this paper produces a more stable and accurate downward continued gravity field when the observed data are corrupted by noise.
{"title":"A nonnegative constrained method for high-precision downward continuation of gravity field data","authors":"Tianyou Liu , Xiaoniu Zeng , Xihai Li , Longwei Chen , Jihao Liu , Xiaofeng Tan , Hongru Li","doi":"10.1016/j.jappgeo.2025.105625","DOIUrl":"10.1016/j.jappgeo.2025.105625","url":null,"abstract":"<div><div>Gravity downward continuation is an effective method for processing and interpreting gravity data. Finding a gravity downward continuation method with high accuracy and stability is a persistent and popular research topic. At present, there are two common strategies for reducing the ill-posedness inherent in the downward continuation of potential fields, namely, regularization, and the design of wavenumber domain filtering operators. However, these downward continuation strategies often result in unsatisfactory continuation accuracy due to excessive smoothing of the downward continued field. To improve the stability and accuracy of the gravity downward continuation calculation, we construct an equivalent mathematical model of gravity downward continuation. This model is not only equivalent to the traditional gravity downward continuation model but also introduces nonnegative constraints into gravity downward continuation. This approach effectively reduces the ill-posedness of gravity downward continuation. Based on the newly proposed gravity downward continuation model, we propose a constrained gravity downward continuation method. Comparison experiments based on a synthetic gravity model and real gravity anomaly data show that, compared with the other four high performance unconstrained potential field downward continuation methods, the constrained downward continuation method proposed in this paper produces a more stable and accurate downward continued gravity field when the observed data are corrupted by noise.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105625"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097099","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2025.105638
Haibo Wu , Yaping Huang , Yanhui Huang , Ze Bai , Jian Lei
The Lamé constants (λ and μ) and anisotropic parameters (ε, γ, and δ) are the key quantities to calculate the brittleness indices and fluid factors in unconventional reservoirs, supporting high-precision seismic data processing as well as anisotropy characterization. However, accurately estimating these quantities using the traditional amplitude variation with offset (AVO) inversion based on the assumption of isotropic media is difficult. Therefore, we conducted a three-parameter AVO inversion and estimated the Lamé constants and P-wave anisotropic parameter (ε) for media with vertically transverse isotropy (VTI), using a coal-measure gas reservoir as an example. A new PP-wave reflection coefficient approximation equation for VTI media was derived based on Rüger's approximation. Subsequently, we analyzed the accuracy of the new equation and designed a strategy for estimating the Lamé constants and P-wave anisotropic parameter. The method was tested and applied using a synthetic seismic record and a cross-well seismic profile. The results demonstrate that the Lamé constants and P-wave anisotropic parameter estimated by both the synthetic seismic record (with or without noise) and cross-well seismic profile (at the well location), agree closely with the well-logging calculated curves. Therefore, the method can reasonably be extended to other similar unconventional reservoirs with certain constraints.
{"title":"Joint Lamé constants and P-wave anisotropic parameter estimation of vertical transverse isotropy coal-measure gas reservoir","authors":"Haibo Wu , Yaping Huang , Yanhui Huang , Ze Bai , Jian Lei","doi":"10.1016/j.jappgeo.2025.105638","DOIUrl":"10.1016/j.jappgeo.2025.105638","url":null,"abstract":"<div><div>The Lamé constants (<em>λ</em> and <em>μ</em>) and anisotropic parameters (<em>ε</em>, <em>γ</em>, and <em>δ</em>) are the key quantities to calculate the brittleness indices and fluid factors in unconventional reservoirs, supporting high-precision seismic data processing as well as anisotropy characterization. However, accurately estimating these quantities using the traditional amplitude variation with offset (AVO) inversion based on the assumption of isotropic media is difficult. Therefore, we conducted a three-parameter AVO inversion and estimated the Lamé constants and P-wave anisotropic parameter (<em>ε</em>) for media with vertically transverse isotropy (VTI), using a coal-measure gas reservoir as an example. A new PP-wave reflection coefficient approximation equation for VTI media was derived based on Rüger's approximation. Subsequently, we analyzed the accuracy of the new equation and designed a strategy for estimating the Lamé constants and P-wave anisotropic parameter. The method was tested and applied using a synthetic seismic record and a cross-well seismic profile. The results demonstrate that the Lamé constants and P-wave anisotropic parameter estimated by both the synthetic seismic record (with or without noise) and cross-well seismic profile (at the well location), agree closely with the well-logging calculated curves. Therefore, the method can reasonably be extended to other similar unconventional reservoirs with certain constraints.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105638"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097102","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2025.105633
Weiying Chen , Wanting Song , Sixu Han , Kangxin Lei , Yulian Zhu
Grounded-wire sources serve as critical transmitting elements in the transient electromagnetic method (TEM). Despite the sustained interest in understanding the impact of grounded-wire sources on the data collected, there remains a notable deficiency in thorough research and discourse on this topic. This study employs numerical simulations and field measurements to investigate the various factors that influence the effects of grounded-wire sources on TEM soundings, particularly focusing on aspects such as size, shape, shallow local anomalies, and the turn-off effect. The findings indicate that the dimensions of the source can significantly affect the early signals observed. Neglecting the actual shape of the source may lead to considerable deviations in the inversion results. Furthermore, local electrical heterogeneities beneath the source can produce overprint effects, resulting in substantial distortions of the observed signals. The turn-off time of the grounded-wire source exhibits a positive correlation with both the source length and the transmitting current, while it shows a negative correlation with grounding resistance. It is recommended that practitioners meticulously document the shape and position of the source. Additionally, it is advisable to position the source in regions characterized by simple and flat geological formations whenever feasible. The design of the source length and the intensity of the transmitting current should be carefully calibrated to accommodate the varying detection requirements for both shallow and deep targets. The implications of this research are significant for the construction, data processing, and interpretation of TEM soundings that utilize grounded-wire sources.
{"title":"Source influences of grounded-wire transient electromagnetic soundings: A systematic review and investigation","authors":"Weiying Chen , Wanting Song , Sixu Han , Kangxin Lei , Yulian Zhu","doi":"10.1016/j.jappgeo.2025.105633","DOIUrl":"10.1016/j.jappgeo.2025.105633","url":null,"abstract":"<div><div>Grounded-wire sources serve as critical transmitting elements in the transient electromagnetic method (TEM). Despite the sustained interest in understanding the impact of grounded-wire sources on the data collected, there remains a notable deficiency in thorough research and discourse on this topic. This study employs numerical simulations and field measurements to investigate the various factors that influence the effects of grounded-wire sources on TEM soundings, particularly focusing on aspects such as size, shape, shallow local anomalies, and the turn-off effect. The findings indicate that the dimensions of the source can significantly affect the early signals observed. Neglecting the actual shape of the source may lead to considerable deviations in the inversion results. Furthermore, local electrical heterogeneities beneath the source can produce overprint effects, resulting in substantial distortions of the observed signals. The turn-off time of the grounded-wire source exhibits a positive correlation with both the source length and the transmitting current, while it shows a negative correlation with grounding resistance. It is recommended that practitioners meticulously document the shape and position of the source. Additionally, it is advisable to position the source in regions characterized by simple and flat geological formations whenever feasible. The design of the source length and the intensity of the transmitting current should be carefully calibrated to accommodate the varying detection requirements for both shallow and deep targets. The implications of this research are significant for the construction, data processing, and interpretation of TEM soundings that utilize grounded-wire sources.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105633"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096571","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2025.105642
Chen Zhao , Jie Liang , Jiajia Zhang , Yinguo Zhang , Jing Sun , Jing Liao
The stochastic seismic amplitude-versus-angle (AVA) inversion is extensively utilized in the estimation of elastic properties and rock physics parameters from seismic data. This method can substantially improve the resolution of reservoir identification in areas where well data are available. Compared with conventional sequential simulation methods, the fast Fourier transform moving average (FFT-MA) simulation exhibits a superior computational efficiency. However, given the limitations of FFT-MA simulation in the simultaneous simulation of multiple elastic properties (such as compressional modulus, VP/VS, and density), the effective application of this method in seismic AVA inversion is challenging. In this study, we propose an FFT-MA co-simulation method for the simultaneous simulation of multiple elastic parameters. This approach establishes possible models constrained by the joint probability distributions of inverted properties, which enhances the accuracy of co-simulated results. Furthermore, we introduce an iterative update method designed to enhance convergence during inversion processes and increase the inversion accuracy. Consequently, an efficient stochastic inversion method is developed through the combination of the FFT-MA Co-simulation method with the iterative update method. The effectiveness of the proposed inversion method is validated through numerical examples and field data application.
{"title":"An improved stochastic inversion of P- to S-wave velocity ratio and compressional modulus based on fast Fourier transform moving average co-simulation","authors":"Chen Zhao , Jie Liang , Jiajia Zhang , Yinguo Zhang , Jing Sun , Jing Liao","doi":"10.1016/j.jappgeo.2025.105642","DOIUrl":"10.1016/j.jappgeo.2025.105642","url":null,"abstract":"<div><div>The stochastic seismic amplitude-versus-angle (AVA) inversion is extensively utilized in the estimation of elastic properties and rock physics parameters from seismic data. This method can substantially improve the resolution of reservoir identification in areas where well data are available. Compared with conventional sequential simulation methods, the fast Fourier transform moving average (FFT-MA) simulation exhibits a superior computational efficiency. However, given the limitations of FFT-MA simulation in the simultaneous simulation of multiple elastic properties (such as compressional modulus, VP/VS, and density), the effective application of this method in seismic AVA inversion is challenging. In this study, we propose an FFT-MA co-simulation method for the simultaneous simulation of multiple elastic parameters. This approach establishes possible models constrained by the joint probability distributions of inverted properties, which enhances the accuracy of co-simulated results. Furthermore, we introduce an iterative update method designed to enhance convergence during inversion processes and increase the inversion accuracy. Consequently, an efficient stochastic inversion method is developed through the combination of the FFT-MA Co-simulation method with the iterative update method. The effectiveness of the proposed inversion method is validated through numerical examples and field data application.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105642"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096573","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2024.105602
Nelson Ricardo Coelho Flores Zuniga , Rafael dos Santos Gioria , Bruno Souza Carmo
Predicting velocity models accurately using FWI technique is strictly related to an enhanced initial estimate. A reliable mean to build a more befitted initial model for FWI provides a more accurate velocity model building and/or fewer iterations — and, therefore, a lower processing time — for building the velocity model. In light of these considerations, we propose to use an approach based on spectral recomposition of elastic seismic data and to implement it in order to perform the optimization of the gradient in initial estimations for FWI focusing in S-waves. This approach employs an inversion scheme aimed at reconstructing the seismic spectrum of wavelets associated with a reflection event. This allows us to estimate the temporal position of each wavelet within a seismogram. Once the temporal position of each wavelet is determined, we can guide the calculated wavelet to better fit the corresponding observed signal, starting from a closer initial point. The utilization of this approach results in notably accurate predictions of elastic velocity models with a significant reduced number of iterations, especially for lower frequencies.
{"title":"Initial gradient optimization for elastic full-waveform inversion by means of spectral recomposition","authors":"Nelson Ricardo Coelho Flores Zuniga , Rafael dos Santos Gioria , Bruno Souza Carmo","doi":"10.1016/j.jappgeo.2024.105602","DOIUrl":"10.1016/j.jappgeo.2024.105602","url":null,"abstract":"<div><div>Predicting velocity models accurately using FWI technique is strictly related to an enhanced initial estimate. A reliable mean to build a more befitted initial model for FWI provides a more accurate velocity model building and/or fewer iterations — and, therefore, a lower processing time — for building the velocity model. In light of these considerations, we propose to use an approach based on spectral recomposition of elastic seismic data and to implement it in order to perform the optimization of the gradient in initial estimations for FWI focusing in S-waves. This approach employs an inversion scheme aimed at reconstructing the seismic spectrum of wavelets associated with a reflection event. This allows us to estimate the temporal position of each wavelet within a seismogram. Once the temporal position of each wavelet is determined, we can guide the calculated wavelet to better fit the corresponding observed signal, starting from a closer initial point. The utilization of this approach results in notably accurate predictions of elastic velocity models with a significant reduced number of iterations, especially for lower frequencies.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105602"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096558","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2024.105603
Zhenjie Feng
Distributed acoustic sensing (DAS) has emerged rapidly in the past decade because of its superb features in sensing the elastic wavefield via a low-cost, high-density, and high-durability manner. The compromise for the unprecedentedly high resolution of DAS is the noise effect. There exists a mixture of many types of noise, including but not limited to random ambient and strong amplitude noise. To tackle the various types of challenging noise, we propose a novel denoising framework based on the dictionary learning scheme. Dictionary learning is comparable to sparse transforms like wavelet and curvelet but outperforms all the alternatives by adaptively learning the basis functions for sparsifying seismic data. Instead of applying dictionary learning in a traditional way as widely reported in the literature, we apply a robust and sophisticated way to real DAS data so that we can best utilize the feature-learning advantages of dictionary learning without sacrificing the signal-leakage problems in traditional denoising methods, especially when it comes to very complicated and noisy DAS datasets.
{"title":"Distributed acoustic sensing data enhancement using an iterative dictionary learning method","authors":"Zhenjie Feng","doi":"10.1016/j.jappgeo.2024.105603","DOIUrl":"10.1016/j.jappgeo.2024.105603","url":null,"abstract":"<div><div>Distributed acoustic sensing (DAS) has emerged rapidly in the past decade because of its superb features in sensing the elastic wavefield via a low-cost, high-density, and high-durability manner. The compromise for the unprecedentedly high resolution of DAS is the noise effect. There exists a mixture of many types of noise, including but not limited to random ambient and strong amplitude noise. To tackle the various types of challenging noise, we propose a novel denoising framework based on the dictionary learning scheme. Dictionary learning is comparable to sparse transforms like wavelet and curvelet but outperforms all the alternatives by adaptively learning the basis functions for sparsifying seismic data. Instead of applying dictionary learning in a traditional way as widely reported in the literature, we apply a robust and sophisticated way to real DAS data so that we can best utilize the feature-learning advantages of dictionary learning without sacrificing the signal-leakage problems in traditional denoising methods, especially when it comes to very complicated and noisy DAS datasets.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105603"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096567","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2025.105623
Li He , Xue Junjie , Fan Kerui , Li Wenhan , Li Xiu
Recently, with the increasing complexity of the topography, geological conditions and working environment in tunnel engineering, rapid and fine detection is significance to the safe construction in tunnel. Transient electromagnetic (TEM) method has advantages in detection of sudden water and mud bursts in tunnels for its characteristic of sensitivity to low resistance anomalous. Focused on tunnel detection, multi-scene and multi-scale detection system of air-ground-underground transient electromagnetic method is analyzed. The research shows that the semi-airborne TEM is efficiently and well-adapted in complex area in the detection depth of 500 m, and the ground TEM has the advantage of large detection depth (2000 m). Moreover, transient electromagnetic advance prediction method has advantages in distinguishing the close adverse geological bodies (100 m) in drilling and Tunnel Boring Machine (TBM) tunnel. Synthesize the advantages of these methods, explore to combine the advanced prediction with the preliminary geological survey to realize the integration of air and sky for efficient exploration.
{"title":"Development of tunnel detection technology using the transient electromagnetic method in China","authors":"Li He , Xue Junjie , Fan Kerui , Li Wenhan , Li Xiu","doi":"10.1016/j.jappgeo.2025.105623","DOIUrl":"10.1016/j.jappgeo.2025.105623","url":null,"abstract":"<div><div>Recently, with the increasing complexity of the topography, geological conditions and working environment in tunnel engineering, rapid and fine detection is significance to the safe construction in tunnel. Transient electromagnetic (TEM) method has advantages in detection of sudden water and mud bursts in tunnels for its characteristic of sensitivity to low resistance anomalous. Focused on tunnel detection, multi-scene and multi-scale detection system of air-ground-underground transient electromagnetic method is analyzed. The research shows that the semi-airborne TEM is efficiently and well-adapted in complex area in the detection depth of 500 m, and the ground TEM has the advantage of large detection depth (2000 m). Moreover, transient electromagnetic advance prediction method has advantages in distinguishing the close adverse geological bodies (100 m) in drilling and Tunnel Boring Machine (TBM) tunnel. Synthesize the advantages of these methods, explore to combine the advanced prediction with the preliminary geological survey to realize the integration of air and sky for efficient exploration.</div></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":"233 ","pages":"Article 105623"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143096577","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}
Pub Date : 2025-02-01DOI: 10.1016/j.jappgeo.2024.105618
G. Apostolopoulos, K. Leontarakis, C. Orfanos, S. Karizonis
Greece, has many important archaeological structures and monuments, as well as a plethora of natural or anthropogenic hazards. Preservation and protection of the monuments are needed, and the deployment of geophysical surveys as part of integrated geoscience and engineering studies play important parts. The Ephorate of Antiquities of Athens had laid plans to undertake restoration works for the Temple of Olympian Zeus, located in the center of Athens, Greece. A geophysical study was completed beforehand to detect the extent of voids found by excavation as well as any other hidden anthropogenic structures around or in the area of the Temple. A 3D electrical resistivity tomography (ERT) survey detected the arched voids, which were used as tanks in the Roman sewer system and later by General Makrygiannis as a place of contemplation, and a complex of tanks to the north of the large ones have been detected by using ground penetrating radar (GPR). A detailed local mode analysis of the subsequent frequency-domain electromagnetic (FEM) survey detected the ancient stone drain lines that brought water to the tanks. A vast surveyed area analysis has detected the distribution of near-surface geological formations. The FEM survey in the area of the Temple has revealed probable rock formations exhibiting two different textures and moisture, in the more loose formation, some linear features align with the existing columns, suggesting that they are probably part of the foundation design for the Temple. These linear features have also been detected by a 3D GPR survey. This multi-proxy geophysical survey provides useful information to guide the program of work that archaeologists and engineers have to carry out in order to protect archaeological monuments and to find hidden features that may create the need for a new design for the site as a whole.
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