Pub Date : 2022-09-02DOI: 10.1080/08123985.2022.2119126
Jizhong Wu, Ying Shi, Weihong Wang, Qianqian Yang
We have presented an inverse filtering scheme that can compensate absorption and dispersion caused by intrinsic attenuation in subsurface media with a heterogeneous model. We have adopted two methods to suppress high-frequency noise at the same time, one is to design a compensation operator with a fixed gain limit, and the other is to introduce an adaptive frequency-varying band calculation method. We use VSP data and seismic velocity data to estimate model of the whole work area in a unique way. The proposed scheme can be incorporated into conventional seismic data processing workflow. Tests on synthetic and real data set demonstrate effectiveness of the proposed inverse filtering.
{"title":"High-resolution imaging: an approach by compensating absorption and dispersion using inverse Q filtering","authors":"Jizhong Wu, Ying Shi, Weihong Wang, Qianqian Yang","doi":"10.1080/08123985.2022.2119126","DOIUrl":"https://doi.org/10.1080/08123985.2022.2119126","url":null,"abstract":"We have presented an inverse filtering scheme that can compensate absorption and dispersion caused by intrinsic attenuation in subsurface media with a heterogeneous model. We have adopted two methods to suppress high-frequency noise at the same time, one is to design a compensation operator with a fixed gain limit, and the other is to introduce an adaptive frequency-varying band calculation method. We use VSP data and seismic velocity data to estimate model of the whole work area in a unique way. The proposed scheme can be incorporated into conventional seismic data processing workflow. Tests on synthetic and real data set demonstrate effectiveness of the proposed inverse filtering.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"253 - 260"},"PeriodicalIF":0.9,"publicationDate":"2022-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46631331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-09-01Epub Date: 2022-06-24DOI: 10.1111/nhs.12957
Lynda J Ross, Lana J Mitchell, Emily C Williams, Patrick J Lynch, Jonathan P Munro, Lauren T Williams
In response to growing evidence that student healthcare professionals find professional practicum stressful and that it negatively affects their mental health, a six-session psychoeducation Resilience and Wellbeing Program was implemented by a professional counselor in Year 3 of the Bachelor of Nutrition and Dietetics at Griffith University, Australia. The aim of this study was to evaluate student dietitians' perceptions of whether the program improved their ability to cope with practicum stressors. The study used a longitudinal cohort design, with students completing surveys at three time points: before and after the program and after the final practicum. The study was completed with two cohorts of students between 2018 and 2020 (n = 111). Most respondents (95%) found their professional practicum to be stressful or challenging on at least some occasions, mostly due to constantly being assessed (56%), finances (40%), and being away from usual supports (38%). Almost all students rated the program as having some value (99%), with the content about stress and self-care the most highly rated. Qualitative comments revealed the program helped students to manage stress by prioritizing their personal needs. Students used stress management skills during the practicum to achieve balance in their lives, despite pandemic conditions.
{"title":"Impact of a resilience and wellbeing program: A longitudinal cohort study of student dietitians.","authors":"Lynda J Ross, Lana J Mitchell, Emily C Williams, Patrick J Lynch, Jonathan P Munro, Lauren T Williams","doi":"10.1111/nhs.12957","DOIUrl":"10.1111/nhs.12957","url":null,"abstract":"<p><p>In response to growing evidence that student healthcare professionals find professional practicum stressful and that it negatively affects their mental health, a six-session psychoeducation Resilience and Wellbeing Program was implemented by a professional counselor in Year 3 of the Bachelor of Nutrition and Dietetics at Griffith University, Australia. The aim of this study was to evaluate student dietitians' perceptions of whether the program improved their ability to cope with practicum stressors. The study used a longitudinal cohort design, with students completing surveys at three time points: before and after the program and after the final practicum. The study was completed with two cohorts of students between 2018 and 2020 (n = 111). Most respondents (95%) found their professional practicum to be stressful or challenging on at least some occasions, mostly due to constantly being assessed (56%), finances (40%), and being away from usual supports (38%). Almost all students rated the program as having some value (99%), with the content about stress and self-care the most highly rated. Qualitative comments revealed the program helped students to manage stress by prioritizing their personal needs. Students used stress management skills during the practicum to achieve balance in their lives, despite pandemic conditions.</p>","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"45 1","pages":"591-600"},"PeriodicalIF":2.1,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9545560/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81132332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-08-30DOI: 10.1080/08123985.2022.2114828
Hongjingtian Zhao, Zhihui Liu, Xue Luo, Yuanyuan Li
Reconstruction of missing seismic data is a critical procedure for subsequent applications like multiple wave suppression, wave-equation migration imaging and so on. In this paper, a fast, hyperparameter-free and sparse iterative spectral estimation approach is proposed for the reconstruction of two-dimensional seismic data of randomly missing traces. The proposed approach is based on the harmonic structure of the frequency slice of seismic data and the weighted covariance fitting criterion. Specifically, the method first iteratively estimates the spectrum of the frequency slice by solving a weighted covariance fitting problem. Then, the missing data is reconstructed by using the estimated spectrum and a linear minimum mean-squared error estimator. However, the spectral estimation depends on matrix-vector multiplications for each iteration, which has a high computational cost when the data increase to a large size. To solve this problem, a fast iterative technology is proposed by using an inverse fast Fourier transform, which fully exploits the Hermitian–Toeplitz structure of the covariance matrix and the exponential form of the steering vector and it significantly reduces the computational complexity. The proposed algorithm is hyperparameter-free, can provide super spectral resolution, and thus obtain better reconstruction performance. The experimental results of synthetic and real seismic data show that the proposed algorithm has higher reconstruction accuracy and lower computational complexity compared to other commonly used reconstruction algorithms.
{"title":"Fast hyperparameter-free spectral approach for 2D seismic data reconstruction","authors":"Hongjingtian Zhao, Zhihui Liu, Xue Luo, Yuanyuan Li","doi":"10.1080/08123985.2022.2114828","DOIUrl":"https://doi.org/10.1080/08123985.2022.2114828","url":null,"abstract":"Reconstruction of missing seismic data is a critical procedure for subsequent applications like multiple wave suppression, wave-equation migration imaging and so on. In this paper, a fast, hyperparameter-free and sparse iterative spectral estimation approach is proposed for the reconstruction of two-dimensional seismic data of randomly missing traces. The proposed approach is based on the harmonic structure of the frequency slice of seismic data and the weighted covariance fitting criterion. Specifically, the method first iteratively estimates the spectrum of the frequency slice by solving a weighted covariance fitting problem. Then, the missing data is reconstructed by using the estimated spectrum and a linear minimum mean-squared error estimator. However, the spectral estimation depends on matrix-vector multiplications for each iteration, which has a high computational cost when the data increase to a large size. To solve this problem, a fast iterative technology is proposed by using an inverse fast Fourier transform, which fully exploits the Hermitian–Toeplitz structure of the covariance matrix and the exponential form of the steering vector and it significantly reduces the computational complexity. The proposed algorithm is hyperparameter-free, can provide super spectral resolution, and thus obtain better reconstruction performance. The experimental results of synthetic and real seismic data show that the proposed algorithm has higher reconstruction accuracy and lower computational complexity compared to other commonly used reconstruction algorithms.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"174 - 188"},"PeriodicalIF":0.9,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42405138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-08-30DOI: 10.1080/08123985.2022.2117603
Yunhui Park, Jong-Kil Hwang
In the implementation of full waveform inversion (FWI) to identify subsurface velocity distributions with land seismic data, which are often acquired in regions with irregular topography, wave equation-based modelling requires caution. In particular, when using the finite difference method (FDM), unwanted scattered waves are generated because irregular surfaces crossing a rectangular grid are discretized via a staircase approximation; hence, if the problems caused by this staircase approximation are disregarded, FDM-based FWI may fail due to the presence of undesirable wavefields. To resolve this problem, this study develops a 2D frequency-domain acoustic FWI technique using a 9-point FDM-based modelling scheme that includes an embedded boundary method (EBM). This study suggests a workflow for the whole EBM-based FWI process from the calculation of coefficients for the EBM-based 9-point FDM modelling to applying it to FWI for proper velocity updates. In numerical examples, using velocity models with a tilted surface and an arbitrarily fluctuating surface, we synthesize seismic data and verify the accuracy of EBM-based 9-point FDM modelling and its superiority over the conventional FDM by comparing it with wavefields derived from the spectral element method. Then, we show that our EBM-based FWI is able to estimate subsurface velocity distributions even though the model has irregular topography, which spoils the result of the conventional FWI.
{"title":"Frequency-domain acoustic full waveform inversion with an embedded boundary method for irregular topography","authors":"Yunhui Park, Jong-Kil Hwang","doi":"10.1080/08123985.2022.2117603","DOIUrl":"https://doi.org/10.1080/08123985.2022.2117603","url":null,"abstract":"In the implementation of full waveform inversion (FWI) to identify subsurface velocity distributions with land seismic data, which are often acquired in regions with irregular topography, wave equation-based modelling requires caution. In particular, when using the finite difference method (FDM), unwanted scattered waves are generated because irregular surfaces crossing a rectangular grid are discretized via a staircase approximation; hence, if the problems caused by this staircase approximation are disregarded, FDM-based FWI may fail due to the presence of undesirable wavefields. To resolve this problem, this study develops a 2D frequency-domain acoustic FWI technique using a 9-point FDM-based modelling scheme that includes an embedded boundary method (EBM). This study suggests a workflow for the whole EBM-based FWI process from the calculation of coefficients for the EBM-based 9-point FDM modelling to applying it to FWI for proper velocity updates. In numerical examples, using velocity models with a tilted surface and an arbitrarily fluctuating surface, we synthesize seismic data and verify the accuracy of EBM-based 9-point FDM modelling and its superiority over the conventional FDM by comparing it with wavefields derived from the spectral element method. Then, we show that our EBM-based FWI is able to estimate subsurface velocity distributions even though the model has irregular topography, which spoils the result of the conventional FWI.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"241 - 252"},"PeriodicalIF":0.9,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45274798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reconstruction of data is a critical preliminary work in the seismic data processing. Compressed sensing (CS) has been well applied in the field of reconstruction. The key point of CS is random sampling, which converts the mutual interference alias caused by regular undersampling into lower-amplitude outside noise. But traditional sampling methods lack constraints on sampling points, emerging too much alias. Segmented random sampling (SRS) effectively controls the distance between sampling points. On the other hand, a single mathematical transformation will lead to incomplete sparse expression and bad restoration effects. Morphological component analysis (MCA) decomposes a signal into several components with outstanding morphological features to approximate the complex internal structure of data. In this paper, we found a new dictionary combination (shearlet + DCT) under the MCA framework and used the block coordinate relaxation algorithm to get the optimal solution to obtain reconstruction results. Tests of 2D data and 3D data have proved that the proposed method can get a better effect when reconstructing the SRS data.
{"title":"Complex structure reconstruction using segmented random sampling and combined dictionary","authors":"De-ying Wang, Kai Zhang, Zhenchun Li, Xin Xu, Yipeng Xu, Yikui Zhang","doi":"10.1080/08123985.2022.2111995","DOIUrl":"https://doi.org/10.1080/08123985.2022.2111995","url":null,"abstract":"The reconstruction of data is a critical preliminary work in the seismic data processing. Compressed sensing (CS) has been well applied in the field of reconstruction. The key point of CS is random sampling, which converts the mutual interference alias caused by regular undersampling into lower-amplitude outside noise. But traditional sampling methods lack constraints on sampling points, emerging too much alias. Segmented random sampling (SRS) effectively controls the distance between sampling points. On the other hand, a single mathematical transformation will lead to incomplete sparse expression and bad restoration effects. Morphological component analysis (MCA) decomposes a signal into several components with outstanding morphological features to approximate the complex internal structure of data. In this paper, we found a new dictionary combination (shearlet + DCT) under the MCA framework and used the block coordinate relaxation algorithm to get the optimal solution to obtain reconstruction results. Tests of 2D data and 3D data have proved that the proposed method can get a better effect when reconstructing the SRS data.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"155 - 173"},"PeriodicalIF":0.9,"publicationDate":"2022-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43396740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-07-28DOI: 10.1080/08123985.2022.2054323
Zean Hu, Lingkai Cao, Rongxin Wu, Guangzhong Ji
Currently, the transmitting channel wave technique mainly uses the attenuation coefficient of the channel wave total energy to explore the geological structure of the coal seam face. In the case of weak geophone coupling and intense geological anomaly, the channel wave energy will be attenuated severely, which significantly affects the stability and accuracy of the result. The Q value of the coal channel is a critical parameter to evaluate the energy attenuation characteristics of the channel wave. The Q value is typically estimated by using the attenuation coefficient of the body wave, but the special coal channel model hinders the estimation of the Q value of the coal seam. According to the linear attenuation characteristics of the centroid frequency of the transmitting channel wave, a new method was proposed to assess the quality factor (Q) of the coal channel by using the centroid frequency change of the channel wave signal. The expected frequency was calculated as its centroid frequency according to the energy ratio of each frequency point through the spectral analysis of the channel wave signal. Combined with the transmission tomography technology, the imaging of the coal seam face based on the transmitting channel wave Q value was established. According to the sudden change of the Q value of the coal channel near the geological structure of the coal seam face, a geological interpretation method based on the abnormal Q value was proposed. The two-dimensional numerical simulation demonstrated that the centroid frequency of the transmitting channel wave signal decayed linearly with the propagation distance and the geological structure increased the frequency shift. Furthermore, three-dimensional numerical simulation validated the feasibility and effectiveness of the Q value inversion method. Field Experimental results showed that the algorithm exhibited improved stability and accuracy. This work proposed a novel frequency-domain inversion method of the transmitting channel wave that directly uses the frequency shift characteristics of the channel wave to estimate the Q value of the coal channel, which offers a new strategy in the data processing of channel wave.
{"title":"Estimation method of coal channel Q value based on frequency shift phenomenon of transmitting channel wave","authors":"Zean Hu, Lingkai Cao, Rongxin Wu, Guangzhong Ji","doi":"10.1080/08123985.2022.2054323","DOIUrl":"https://doi.org/10.1080/08123985.2022.2054323","url":null,"abstract":"Currently, the transmitting channel wave technique mainly uses the attenuation coefficient of the channel wave total energy to explore the geological structure of the coal seam face. In the case of weak geophone coupling and intense geological anomaly, the channel wave energy will be attenuated severely, which significantly affects the stability and accuracy of the result. The Q value of the coal channel is a critical parameter to evaluate the energy attenuation characteristics of the channel wave. The Q value is typically estimated by using the attenuation coefficient of the body wave, but the special coal channel model hinders the estimation of the Q value of the coal seam. According to the linear attenuation characteristics of the centroid frequency of the transmitting channel wave, a new method was proposed to assess the quality factor (Q) of the coal channel by using the centroid frequency change of the channel wave signal. The expected frequency was calculated as its centroid frequency according to the energy ratio of each frequency point through the spectral analysis of the channel wave signal. Combined with the transmission tomography technology, the imaging of the coal seam face based on the transmitting channel wave Q value was established. According to the sudden change of the Q value of the coal channel near the geological structure of the coal seam face, a geological interpretation method based on the abnormal Q value was proposed. The two-dimensional numerical simulation demonstrated that the centroid frequency of the transmitting channel wave signal decayed linearly with the propagation distance and the geological structure increased the frequency shift. Furthermore, three-dimensional numerical simulation validated the feasibility and effectiveness of the Q value inversion method. Field Experimental results showed that the algorithm exhibited improved stability and accuracy. This work proposed a novel frequency-domain inversion method of the transmitting channel wave that directly uses the frequency shift characteristics of the channel wave to estimate the Q value of the coal channel, which offers a new strategy in the data processing of channel wave.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"79 - 87"},"PeriodicalIF":0.9,"publicationDate":"2022-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43880192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-06-24DOI: 10.1080/08123985.2022.2092725
Yipeng Xu, Kai Zhang, Zhenchun Li, Ziling He, Jichuan Wang, De-ying Wang
The weak signals of artificial seismic records contain the subsurface medium information that is required in the inversion. But in the full waveform inversion (FWI), the weak signals contribute less to the objective functions. Therefore, how to improve the contribution of the weak signals in the objective functions of FWI is the problem that needs to be solved urgently. The research shows (Ren, D. 1980. Preliminary research on seismic record and instantaneous frequency. Oil Geophysical Prospecting 15 no. 1: 7–21) that instantaneous frequency attributes, which are very sensitive to the changes in subsurface velocity, have the potential to extract the weak signals from the seismic records. However, this frequency can only be estimated from the complex seismic signals. Empirical mode decomposition (EMD) method has been widely used in signal analysis so as to estimate the instantaneous frequency, but it is difficult to be applied in FWI due to the huge computation. In order to solve this problem, the instantaneous frequency is replaced with the first-order approximation of the exponential frequency in FWI. In this paper, the objective functions of the first-order approximate exponential frequency FWI (FRE-EFWI) in elastic waves and the source terms of its back propagation formula were derived. Besides, the FRE-EFWI method was proved to improve the contribution of the weak signals in the objective functions of FWI. In addition, the correctness and effectiveness of the method were demonstrated by the examples of FWI.
人工地震记录的微弱信号包含了反演所需的地下介质信息。但在全波形反演(FWI)中，弱信号对目标函数的贡献较小。因此，如何提高弱信号在FWI目标函数中的贡献是目前迫切需要解决的问题。研究表明(Ren, D. 1980)。地震记录与瞬时频率的初步研究。石油地球物理勘探15期(1: 7-21)瞬时频率属性对地下速度变化非常敏感，有可能从地震记录中提取微弱信号。然而，这个频率只能从复杂的地震信号中估计出来。经验模态分解(EMD)方法已广泛应用于信号分析中以估计瞬时频率，但由于计算量大，难以应用于FWI。为了解决这一问题，在FWI中将瞬时频率替换为指数频率的一阶近似。本文推导了弹性波中一阶近似指数频率FWI (frei - efwi)的目标函数及其反向传播公式的源项。此外，还证明了该方法可以提高弱信号在FWI目标函数中的贡献。最后，通过FWI算例验证了该方法的正确性和有效性。
{"title":"Time domain elastic-wave full waveform inversion based on first-order approximate instantaneous frequency","authors":"Yipeng Xu, Kai Zhang, Zhenchun Li, Ziling He, Jichuan Wang, De-ying Wang","doi":"10.1080/08123985.2022.2092725","DOIUrl":"https://doi.org/10.1080/08123985.2022.2092725","url":null,"abstract":"The weak signals of artificial seismic records contain the subsurface medium information that is required in the inversion. But in the full waveform inversion (FWI), the weak signals contribute less to the objective functions. Therefore, how to improve the contribution of the weak signals in the objective functions of FWI is the problem that needs to be solved urgently. The research shows (Ren, D. 1980. Preliminary research on seismic record and instantaneous frequency. Oil Geophysical Prospecting 15 no. 1: 7–21) that instantaneous frequency attributes, which are very sensitive to the changes in subsurface velocity, have the potential to extract the weak signals from the seismic records. However, this frequency can only be estimated from the complex seismic signals. Empirical mode decomposition (EMD) method has been widely used in signal analysis so as to estimate the instantaneous frequency, but it is difficult to be applied in FWI due to the huge computation. In order to solve this problem, the instantaneous frequency is replaced with the first-order approximation of the exponential frequency in FWI. In this paper, the objective functions of the first-order approximate exponential frequency FWI (FRE-EFWI) in elastic waves and the source terms of its back propagation formula were derived. Besides, the FRE-EFWI method was proved to improve the contribution of the weak signals in the objective functions of FWI. In addition, the correctness and effectiveness of the method were demonstrated by the examples of FWI.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"144 - 154"},"PeriodicalIF":0.9,"publicationDate":"2022-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43361390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-06-21DOI: 10.1080/08123985.2022.2089013
T. Kasaya, Y. Nogi, K. Kitada
Marine magnetic field surveys conducted near the sea bottom are useful in producing images of the oceanic crust in order to ascertain its volcanic eruption history, active hydrothermal systems, and hydrothermal deposit evolution. An autonomous underwater vehicle (AUV) can carry out self-controlled survey operations while maintaining a stable vehicle attitude at low altitudes above the seafloor. As a result of these benefits, AUVs have attracted attention for various missions. The total magnetic field intensity is generally used for subsurface magnetization images. Recently, vector magnetic anomaly analysis has been considered to be extremely effective for high-accuracy estimation of subsurface magnetization structures. However, correcting for the anomalous magnetic field produced by the vehicle body is one of the difficulties that hinders vector magnetic anomaly analysis. Therefore, we developed a magnetometer system designed for the AUV URASHIMA with a renewed navigation data distribution system. Experimental observation was carried out around a submarine mud volcano with a small magnetic anomaly off Tanegashima Island. The results show that correction for the magnetic field of the vehicle because of the attitude, especially for changes in pitch, is essential for near-bottom magnetic surveys using AUVs. Based on these results, we proposed a suitable data acquisition method to remove the pitching effects of the vehicle for figure-eight turns. Next, practical observation was carried out in the hydrothermal area, and the proposed correction method for magnetic data reduced the pitch variation effect. These results indicate that the correction for the magnetic field of the vehicle based using attitude data, especially for pitching variations, is required in order to obtain high-quality magnetic anomaly data using AUVs. However, a short-period variation of approximately 10 nT caused by abrupt pitch changes remains.
{"title":"Advanced magnetic survey system and method for detailed magnetic field mapping near the sea bottom using an autonomous underwater vehicle","authors":"T. Kasaya, Y. Nogi, K. Kitada","doi":"10.1080/08123985.2022.2089013","DOIUrl":"https://doi.org/10.1080/08123985.2022.2089013","url":null,"abstract":"Marine magnetic field surveys conducted near the sea bottom are useful in producing images of the oceanic crust in order to ascertain its volcanic eruption history, active hydrothermal systems, and hydrothermal deposit evolution. An autonomous underwater vehicle (AUV) can carry out self-controlled survey operations while maintaining a stable vehicle attitude at low altitudes above the seafloor. As a result of these benefits, AUVs have attracted attention for various missions. The total magnetic field intensity is generally used for subsurface magnetization images. Recently, vector magnetic anomaly analysis has been considered to be extremely effective for high-accuracy estimation of subsurface magnetization structures. However, correcting for the anomalous magnetic field produced by the vehicle body is one of the difficulties that hinders vector magnetic anomaly analysis. Therefore, we developed a magnetometer system designed for the AUV URASHIMA with a renewed navigation data distribution system. Experimental observation was carried out around a submarine mud volcano with a small magnetic anomaly off Tanegashima Island. The results show that correction for the magnetic field of the vehicle because of the attitude, especially for changes in pitch, is essential for near-bottom magnetic surveys using AUVs. Based on these results, we proposed a suitable data acquisition method to remove the pitching effects of the vehicle for figure-eight turns. Next, practical observation was carried out in the hydrothermal area, and the proposed correction method for magnetic data reduced the pitch variation effect. These results indicate that the correction for the magnetic field of the vehicle based using attitude data, especially for pitching variations, is required in order to obtain high-quality magnetic anomaly data using AUVs. However, a short-period variation of approximately 10 nT caused by abrupt pitch changes remains.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"205 - 216"},"PeriodicalIF":0.9,"publicationDate":"2022-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48101919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-06-10DOI: 10.1080/08123985.2022.2086798
Jihun Choi, J. Byun, S. Seol, Seong Kon Lee
Microseismic monitoring is widely used to analyze the locations and growth directions of fractures formed at sites of hydraulic fracturing treatment and CO2 geologic sequestration. Because moment tensors can provide focal mechanisms, moment tensor inversion has received considerable attention in microseismic monitoring; the real-time processing of moment tensor inversion is important for rapid decision-making. Pre-trained machine learning (ML) models can make nearly instantaneous predictions in the application stage and thus present an attractive alternative to real-time processing. However, prior information regarding the velocity model at the target site is a prerequisite for generating the dataset used to train the ML model that is applied in moment tensor inversion. In addition, it is difficult to create the training dataset because it requires three-dimensional numerical modelling when the velocity model is complex; numerous simulations must be executed for sources with various locations and moment tensors. To overcome these limitations, we applied the domain adaptation technique to the convolutional neural network (CNN)-based moment tensor inversion method, which uses peak amplitudes and arrival times of P- and S-waves as input features. The CNN model was pre-trained with the dataset generated from a homogeneous velocity model. Then, in the domain adaptation stage, the pre-trained model was fine-tuned along with the target dataset. To validate the performance of the domain adaptation, moment tensors from both horizontal and tilted three-layer models were predicted. In each case, the domain-adapted model performance was similar to the performances of the CNN-based models that had been trained using the dataset generated with the exact target velocity models.
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Pub Date : 2022-06-10DOI: 10.1080/08123985.2022.2086040
F. Dirgantara, A. Lin, Char‐Shine Liu
Reducing multiple contaminations in reflection seismic data remains one of the primary challenges in marine seismic data processing. Besides geological settings, its effectiveness is also dependent on the multiple removal methods. In this study, we undertook two legacy 2D multi-channel seismic data crossing the accretionary wedge off SW Taiwan to test the efficiency of various multiple-attenuation scenarios. The tectonic domain has resulted from the incipient arc-continent collision between the northern rifted margin of the South China Sea and the Luzon volcanic arc. The wedge extends from shallow water to deep water bathymetries, hence promoting both short-period and long-period multiples within the seismic records. A cascade of de-multiple methods was tested to attenuate multiple energy under various seafloor bathymetry and tectonic areas. The first step relies on the periodicity nature of multiples. Spatial dependent predictive deconvolution in the x-t domain was performed to attenuate reverberations and improve temporal resolution in the time domain. Wave-equation multiple attenuation (WEMA) was applied to suppress the water layer multiples based on a combination of numerical wave extrapolation in the shot domain through water layer and water bottom reflectivity. Surface-related multiple elimination (SRME) aimed to attenuate the residual water bottom multiple and peg-leg multiple by assuming surface-related multiples can be kinematically predicted via convolution of pre-stack seismic traces at possible surface multiple reflection locations. The second step exploits the spatial move-out difference behavior between primaries and multiples. Parabolic Radon transforms far-offset multiples by subtracting noise energy in the τ-p domain, whereas the frequency-wave number (F-K) filter aimed to eliminate any residual multiples energy in the F-K domain. Predictive deconvolution improved seismic resolution and suppressed sea-bottom reverberation energy in the continental and lower wedge slopes, but not in the upper wedge slope. WEMA, Radon filter, and F-K filter reduced multiples energy both at the continental slope and wedge slope; whereas SRME made minimal impact on both areas. Since the reflection seismic datasets stretch diverse tectonic environments and water depth, there was no single multiple attenuation method capable to suppress multiples in all tectonic environments and bathymetry.
{"title":"Seismic de-multiple strategy in the submarine slope of Taiwan accretionary wedge","authors":"F. Dirgantara, A. Lin, Char‐Shine Liu","doi":"10.1080/08123985.2022.2086040","DOIUrl":"https://doi.org/10.1080/08123985.2022.2086040","url":null,"abstract":"Reducing multiple contaminations in reflection seismic data remains one of the primary challenges in marine seismic data processing. Besides geological settings, its effectiveness is also dependent on the multiple removal methods. In this study, we undertook two legacy 2D multi-channel seismic data crossing the accretionary wedge off SW Taiwan to test the efficiency of various multiple-attenuation scenarios. The tectonic domain has resulted from the incipient arc-continent collision between the northern rifted margin of the South China Sea and the Luzon volcanic arc. The wedge extends from shallow water to deep water bathymetries, hence promoting both short-period and long-period multiples within the seismic records. A cascade of de-multiple methods was tested to attenuate multiple energy under various seafloor bathymetry and tectonic areas. The first step relies on the periodicity nature of multiples. Spatial dependent predictive deconvolution in the x-t domain was performed to attenuate reverberations and improve temporal resolution in the time domain. Wave-equation multiple attenuation (WEMA) was applied to suppress the water layer multiples based on a combination of numerical wave extrapolation in the shot domain through water layer and water bottom reflectivity. Surface-related multiple elimination (SRME) aimed to attenuate the residual water bottom multiple and peg-leg multiple by assuming surface-related multiples can be kinematically predicted via convolution of pre-stack seismic traces at possible surface multiple reflection locations. The second step exploits the spatial move-out difference behavior between primaries and multiples. Parabolic Radon transforms far-offset multiples by subtracting noise energy in the τ-p domain, whereas the frequency-wave number (F-K) filter aimed to eliminate any residual multiples energy in the F-K domain. Predictive deconvolution improved seismic resolution and suppressed sea-bottom reverberation energy in the continental and lower wedge slopes, but not in the upper wedge slope. WEMA, Radon filter, and F-K filter reduced multiples energy both at the continental slope and wedge slope; whereas SRME made minimal impact on both areas. Since the reflection seismic datasets stretch diverse tectonic environments and water depth, there was no single multiple attenuation method capable to suppress multiples in all tectonic environments and bathymetry.","PeriodicalId":50460,"journal":{"name":"Exploration Geophysics","volume":"54 1","pages":"117 - 132"},"PeriodicalIF":0.9,"publicationDate":"2022-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47180710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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