The Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system was designed by the First Institute of Oceanography,Ministry of Natural Resources(FIO,MNR).The system is mainly composed of a plasma spark sour...The Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system was designed by the First Institute of Oceanography,Ministry of Natural Resources(FIO,MNR).The system is mainly composed of a plasma spark source(source level:216 dB,main frequency:750 Hz,frequency bandwidth:150-1200 Hz)and a towed hydrophone streamer with 48 channels.Because the source and the towed hydrophone streamer are constantly moving according to the towing configuration,the accurate positioning of the towing hydrophone array and the moveout correction of deep-towed multichannel seismic data processing before imaging are challenging.Initially,according to the characteristics of the system and the towing streamer shape in deep water,travel-time positioning method was used to construct the hydrophone streamer shape,and the results were corrected by using the polynomial curve fitting method.Then,a new data-processing workflow for Kuiyang-ST2000 system data was introduced,mainly including float datum setting,residual static correction,phase-based moveout correction,which allows the imaging algorithms of conventional marine seismic data processing to extend to deep-towed seismic data.We successfully applied the Kuiyang-ST2000 system and methodology of data processing to a gas hydrate survey of the Qiongdongnan and Shenhu areas in the South China Sea,and the results show that the profile has very high vertical and lateral resolutions(0.5 m and 8 m,respectively),which can provide full and accurate details of gas hydrate-related and geohazard sedimentary and structural features in the South China Sea.展开更多
(Multichannel)Singular spectrum analysis is considered as one of the most effective methods for seismic incoherent noise suppression.It utilizes the low-rank feature of seismic signal and regards the noise suppression...(Multichannel)Singular spectrum analysis is considered as one of the most effective methods for seismic incoherent noise suppression.It utilizes the low-rank feature of seismic signal and regards the noise suppression as a low-rank reconstruction problem.However,in some cases the seismic geophones receive some erratic disturbances and the amplitudes are dramatically larger than other receivers.The presence of this kind of noise,called erratic noise,makes singular spectrum analysis(SSA)reconstruction unstable and has undesirable effects on the final results.We robustify the low-rank reconstruction of seismic data by a reweighted damped SSA(RD-SSA)method.It incorporates the damped SSA,an improved version of SSA,into a reweighted framework.The damping operator is used to weaken the artificial disturbance introduced by the low-rank projection of both erratic and random noise.The central idea of the RD-SSA method is to iteratively approximate the observed data with the quadratic norm for the first iteration and the Tukeys bisquare norm for the rest iterations.The RD-SSA method can suppress seismic incoherent noise and keep the reconstruction process robust to the erratic disturbance.The feasibility of RD-SSA is validated via both synthetic and field data examples.展开更多
There is little low-and-high frequency information on seismic data in seismic exploration,resulting in narrower bandwidth and lower seismic resolution.It considerably restricts the prediction accuracy of thin reservoi...There is little low-and-high frequency information on seismic data in seismic exploration,resulting in narrower bandwidth and lower seismic resolution.It considerably restricts the prediction accuracy of thin reservoirs and thin interbeds.This study proposes a novel method to constrain improving seismic resolution in the time and frequency domain.The expected wavelet spectrum is used in the frequency domain to broaden the seismic spectrum range and increase the octave.In the time domain,the Frobenius vector regularization of the Hessian matrix is used to constrain the horizontal continuity of the seismic data.It eff ectively protects the signal-to-noise ratio of seismic data while the longitudinal seismic resolution is improved.This method is applied to actual post-stack seismic data and pre-stack gathers dividedly.Without abolishing the phase characteristics of the original seismic data,the time resolution is signifi cantly improved,and the structural features are clearer.Compared with the traditional spectral simulation and deconvolution methods,the frequency distribution is more reasonable,and seismic data has higher resolution.展开更多
A novel technique for automatic seismic data processing using both integral and local feature of seismograms was presented in this paper. Here, the term integral feature of seismograms refers to feature which may depi...A novel technique for automatic seismic data processing using both integral and local feature of seismograms was presented in this paper. Here, the term integral feature of seismograms refers to feature which may depict the shape of the whole seismograms. However, unlike some previous efforts which completely abandon the DIAL approach, i.e., signal detection, phase identifi- cation, association, and event localization, and seek to use envelope cross-correlation to detect seismic events directly, our technique keeps following the DIAL approach, but in addition to detect signals corresponding to individual seismic phases, it also detects continuous wave-trains and explores their feature for phase-type identification and signal association. More concrete ideas about how to define wave-trains and combine them with various detections, as well as how to measure and utilize their feature in the seismic data processing were expatiated in the paper. This approach has been applied to the routine data processing by us for years, and test results for a 16 days＇ period using data from the Xinjiang seismic station network were presented. The automatic processing results have fairly low false and missed event rate simultaneously, showing that the new technique has good application prospects for improvement of the automatic seismic data processing.展开更多
A comprehensive study of the data profiles, including the 2D seismic data, single channel seismic data, shallow sections, etc., reveals that gas hydrates occur in the East China Sea. A series of special techniques are...A comprehensive study of the data profiles, including the 2D seismic data, single channel seismic data, shallow sections, etc., reveals that gas hydrates occur in the East China Sea. A series of special techniques are used in the processing of seismic data, which include enhancing the accuracy of velocity analysis and resolution, estimating the wavelet, suppressing the multiple, preserving the relative amplitude, using the DMO and AVO techniques and some special techniques in dealing with the wave impedance. The existence of gas hydrates is reflected in the subbottom profiles in the appearance of BSRs, amplitude anomalies, velocity anomalies and AVO anomalies, etc. Hence the gas hydrates can be identified and predicted. It is pointed out that the East China Sea is a favorable area of the gas hydrates resource, and the Okinawa Trough is a target area of gas hydrates reservoir.展开更多
Branching river channels and the coexistence of valleys, ridges, hiils, and slopes＇as the result of long-term weathering and erosion form the unique loess topography. The Changqing Geophysical Company, working in the...Branching river channels and the coexistence of valleys, ridges, hiils, and slopes＇as the result of long-term weathering and erosion form the unique loess topography. The Changqing Geophysical Company, working in these complex conditions, has established a suite of technologies for high-fidelity processing and fine interpretation of seismic data. This article introduces the processes involved in the data processing and interpretation and illustrates the results.展开更多
The seismic reflection method is one of the most important methods in geophysical exploration.There are three stages in a seismic exploration survey:acquisition,processing,and interpretation.This paper focuses on a pr...The seismic reflection method is one of the most important methods in geophysical exploration.There are three stages in a seismic exploration survey:acquisition,processing,and interpretation.This paper focuses on a pre-processing tool,the Non-Local Means(NLM)filter algorithm,which is a powerful technique that can significantly suppress noise in seismic data.However,the domain of the NLM algorithm is the whole dataset and 3D seismic data being very large,often exceeding one terabyte(TB),it is impossible to store all the data in Random Access Memory(RAM).Furthermore,the NLM filter would require a considerably long runtime.These factors make a straightforward implementation of the NLM algorithm on real geophysical exploration data infeasible.This paper redesigned and implemented the NLM filter algorithm to fit the challenges of seismic exploration.The optimized implementation of the NLM filter is capable of processing production-size seismic data on modern clusters and is 87 times faster than the straightforward implementation of NLM.展开更多
In this paper, multi-scaled morphology is introduced into the digital processing domain for land seismic data. First, we describe the basic theory of multi-scaled morphology image decomposition of exploration seismic ...In this paper, multi-scaled morphology is introduced into the digital processing domain for land seismic data. First, we describe the basic theory of multi-scaled morphology image decomposition of exploration seismic waves; second, we illustrate how to use multi-scaled morphology for seismic data processing using two real examples. The first example demonstrates suppressing the surface waves in pre-stack seismic records using multi-scaled morphology decomposition and reconstitution and the other example demonstrates filtering different interference waves on the seismic record. Multi-scaled morphology filtering separates signal from noise by the detailed differences of the wave shapes. The successful applications suggest that multi-scaled morphology has a promising application in seismic data processing.展开更多
Subduction zones can generally be classified into Mariana type and Chilean type depending on plate ages, plate thicknesses, subduction angles, back-arc deformation patterns, etc. The double seismic zones （DSZs） in s...Subduction zones can generally be classified into Mariana type and Chilean type depending on plate ages, plate thicknesses, subduction angles, back-arc deformation patterns, etc. The double seismic zones （DSZs） in sub- duction zones are mainly divided into type I and type II which, respectively, correspond to the Mariana type and Chilean type in most cases. Seismic anisotropy is an important parameter characterizing the geophysical fea- tures of the lithosphere, including the subduction zones, and can be described by the two parameters of delay time ~t and fast wave polarization direction ~b. We totally col- lected 524 seismic anisotropy data records from 24 DSZs and analyzed the statistical correlations between seismic anisotropy and the related physical parameters of DSZs. Our statistical analysis demonstrated that the fast wave polarization directions are parallel to the trench strike with no more than 30~ for most type I DSZs, while being nearlyperpendicular to the trench strike for type II DSZs. We also calculated roughly linear correlations that the delay time 6t increases with dip angles but decreases with subduction rates. A linear equation was summarized to describe the strong correlation between DSZ＇s subduction angle DSZ and seismic anisotropy in subduction zones. These results suggest that the anisotropic structure of the subducting lithosphere can be described as a possible equivalent crystal similar to the olivine crystal with three mutually orthogonal polarization axes, of which the longest and the second axes are nearly along the trench-perpendicular and trench-parallel directions, respectively.展开更多
Data processing is a basic and crucial factor in seismic exploration,which can influence the effect of subsequent processing directly. Thus the selection of appropriate method for data processing is one of the most im...Data processing is a basic and crucial factor in seismic exploration,which can influence the effect of subsequent processing directly. Thus the selection of appropriate method for data processing is one of the most important tasks throughout the work. By simulating,the authors analyze and compare Fractional Fourier Transform( FRFT) and Wigner-Ville distribution( WVD),then summarize the similarities and advantages and disadvantages of the two methods. The results reveal that FRFT is more effective and suitable for application in seismic exploration than WVD.展开更多
Recent geodetic and seismological observations of two major earthquakes in southeastern Türkiye in February 2023 have revealed complex rupture initiation,propagation,and segmentation along the East Anatolian Faul...Recent geodetic and seismological observations of two major earthquakes in southeastern Türkiye in February 2023 have revealed complex rupture initiation,propagation,and segmentation along the East Anatolian Fault Zone(EAFZ)and surrounding regions.However,the role of upper crust structures along the EAFZ in determining the diverse rupture processes of this earthquake doublet remains unclear.To further investigate this,we employed double-difference location and seismic tomography techniques to determine high-resolution seismic velocities(V_(P),V_(S))and Poisson’s ratio(σ)structures using a multiparameter joint tomographic algorithm.Our dataset includes 100,833 high-quality source-receiver travel-time pairs of P-and Swaves.We find that the unique rupture processes of this earthquake doublet were primarily influenced by contrasting crustal seismic structures and localized geological settings.The M_(w)7.8 mainshock was initiated within a transitional edge zone characterized by a rigid part(asperity)of the seismogenic zone with sharp contrast variations in rock strength ranging from low to high along the EAFZ.In comparison,the M_(w)7.6 rupture originated in a ductile belt featuring fluid saturation with low-VP,low-VS,and high-σvalues that extended parallel to the Cardak Fault.The pronounced contrast structures observed along the former rupture can be attributed to the oblique collision system between the weakened section of the east Anatolian plateau and the brittle Arabian platform,while the latter rupture was initiated within the ductile structure associated with fluid intrusion caused by the northward subduction of the Cyprus slab and subsequent detachment.Furthermore,the occurrence of the first earthquake(E1)serves to alleviate shear stress on the second earthquake(E2)fault,potentially impeding the initiation of an E2 rupture.On the contrary,this event also significantly reduces the normal stress acting on the E2 fault due to a double left-lateral strike-slip system within a triangular region.This reduction not only results in a decrease of fault friction force and an increase in rock porosity but also induces lower strain drops and the redistribution of Coulomb stress,thereby contributing to the initiation of the E2 event.The proposed rupture pattern exceeds the conventional model that governs individual earthquake ruptures,offering new insights for mitigating potential seismic disasters in Türkiye.The lessons learned from this doublet event can contribute to reevaluating the ongoing risk of damaging earthquakes in China’s South-North Seismic Zone or other regions worldwide with comparable geological conditions.展开更多
Attenuation of migration artifacts on Kirchhoff migrated seismic data can be challenging due to the relatively low amplitude of migration artifacts compared to reflections as well as the overlap in the kinematics of r...Attenuation of migration artifacts on Kirchhoff migrated seismic data can be challenging due to the relatively low amplitude of migration artifacts compared to reflections as well as the overlap in the kinematics of reflection and migration smiles.Several‘conventional’filtering methods exist and recently deep learning based workflows have been proposed.A deep learning workflow can be a simple and fast alternative to existing methods.In case of supervised training of a deep neural network using training data made by physics-based modelling or actual migrations is expensive and lacks diversity in terms of noise,amplitude,frequency content and wavelet.This can result in poor generalization beyond the training data without re-training and transfer learning.In this paper we demonstrate successful applications of migration smile separation using a conventional U-net architecture.The novelty in our approach is that we do not use synthetic data created from physics-based modelling,but instead use only synthetic data build form basic geometric shapes.Our domain of application is the migrated common offset domain,or simply the stack of the pre-stack migrated data,where reflections resemble local geology and migration smiles are upward convex hyperbolic patterns.Both patterns were randomly perturbed in many ways while maintaining their intrinsic features.This approach is inspired by the common practice of data augmentation in deep learning for machine vision applications.Since many of the standard data augmentation techniques lack a geophysical motivation,we have instead perturbed our synthetic training data in ways to make more sense for a signal processing perspective or given our‘domain knowledge’of the problem at hand.We did not have to retrain the network to produce good results on the field dataset.The large variety and diversity in examples enabled the trained neural network to show encouraging results on synthetic and field datasets that were not used in training.展开更多
For thin gas reservoir of low-porosity and low-permeability in the loess desert area, a suite of lateral reservoir prediction techniques has been developed by Changqing Oil Company and the excellent effects achieved i...For thin gas reservoir of low-porosity and low-permeability in the loess desert area, a suite of lateral reservoir prediction techniques has been developed by Changqing Oil Company and the excellent effects achieved in exploration and exploitation in the areas such as Yulin, Wushenqi,Suligemiao, Shenmu etc., so that the Upper Paleozoic gas reserve has been stably increasing for eight years in Changqing Oilfield. The paper analyzed the effects and experience of the application of these techniques in detail.展开更多
On 25 April, 2015, an Mw7.9 earthquake occurred in Nepal, which caused great economic loss and casualties. However, almost no surface ruptures were observed. Therefore, in order to interpret the phenomenon, we study t...On 25 April, 2015, an Mw7.9 earthquake occurred in Nepal, which caused great economic loss and casualties. However, almost no surface ruptures were observed. Therefore, in order to interpret the phenomenon, we study the rupture process of the earthquake to seek answers. Inversion of teleseismic body-wave data is applied to estimate the rupture process of the 2015 Nepal earthquake. To obtain stable solutions, smoothing and non-negative constraints are introduced. 48 teleseismic stations with good coverage are chosen. Finite fault model is established with length and width of 195 km and 150 km, and we set the initial seismic source parameters referring to CMT solutions. Inversion results indicate that the focal mechanism of this earthquake is a thrust fault type, and the strike, dip and rake angle are in accordance with CMT results. The seismic moment is 0.9195 ×10^（21）Nm（Mw7.9）, and source duration is about 70s. The rupture nucleated near the hypocenter and then propagated along the dip direction to the southeast, and the maximum slip amounts to 5.2 m. Uncertainties on the amount of slip retrieved by different inversion methods still exist, the overall characteristics are inconsistent. The lack of shallow slip during the 2015 Gorkha earthquake implies future seismic hazard and this region should be paid more attention to.展开更多
The strong earthquakes in western Yunnan area, mainly occur along great interplate strike slip faults and have a dominant depth layer about 10～20 km; the seismic rupture is characterized by strike slip rupture. Co...The strong earthquakes in western Yunnan area, mainly occur along great interplate strike slip faults and have a dominant depth layer about 10～20 km; the seismic rupture is characterized by strike slip rupture. Considering the Yunnan lithospheric structure and dynamic background, we think that earthquakes occurring at this area might have such a kind of nucleation process: because of the multi layers and heterogeneities of lithospheric structure, a zone of concentrated shear strain or of slip might be formed at the moderate or deep portions of lithosphere, and spread upward along faulting boundary, toward the earths surface under the background field of tectonic movement of lithospheric plates. The slip front will encounter the maximum shear resistance zone on the fault surface in this process, be barried and blocked, and form a seismic gap. With the increase of tectonic load, this slip zone will continuously spread forward, traverse and lead to instable crack of the whole blocked zone, and cause a great earthquake. We have derived an approximate integral equation describing this seismic process; the numerical results show that the model has an instable nonlinear accelerating evolution period which might have important significance for the generation of earthquake precursors.展开更多
The seismicity characteristics of the earthquake swarm occurred in Datong area in Shanxi Province during 1989-1993 period are studied in detail. The focal mechanisms and rupture processes of the principal earthquakes ...The seismicity characteristics of the earthquake swarm occurred in Datong area in Shanxi Province during 1989-1993 period are studied in detail. The focal mechanisms and rupture processes of the principal earthquakes in itare also estimated in this paper. A mechanical model of fracture system of asymmetrical conjugate array is suggested from the view point of fracture propagation in order to simulate the mechanical features in the seismicsource respect of the Datong swarm sequence. The computation results of displacement field, stress field andstrain energy distribution from this model by using finite element method are presented. In addition, somerecorded data of geothermal precursors before these three climaxes of the Datong earthquake swarm sequence arediscussed mainly in this paper.展开更多
This work pertains to numerical aspects of a finite element method based discontinuous functions.Our study focuses on the Interior Penalty Discontinuous Galerkin method(IPDGM)because of its high-level of flexibility f...This work pertains to numerical aspects of a finite element method based discontinuous functions.Our study focuses on the Interior Penalty Discontinuous Galerkin method(IPDGM)because of its high-level of flexibility for solving the full wave equation in heterogeneousmedia.We assess the performance of IPDGMthrough a comparison study with a spectral element method(SEM).We show that IPDGM is as accurate as SEM.In addition,we illustrate the efficiency of IPDGM when employed in a seismic imaging process by considering two-dimensional problems involving the Reverse Time Migration.展开更多
基金Supported by the National Key R&D Program of China(No.2016YFC0303900)the Laoshan Laboratory(Nos.MGQNLM-KF201807,LSKJ202203604)the National Natural Science Foundation of China(No.42106072)。
文摘The Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system was designed by the First Institute of Oceanography,Ministry of Natural Resources(FIO,MNR).The system is mainly composed of a plasma spark source(source level:216 dB,main frequency:750 Hz,frequency bandwidth:150-1200 Hz)and a towed hydrophone streamer with 48 channels.Because the source and the towed hydrophone streamer are constantly moving according to the towing configuration,the accurate positioning of the towing hydrophone array and the moveout correction of deep-towed multichannel seismic data processing before imaging are challenging.Initially,according to the characteristics of the system and the towing streamer shape in deep water,travel-time positioning method was used to construct the hydrophone streamer shape,and the results were corrected by using the polynomial curve fitting method.Then,a new data-processing workflow for Kuiyang-ST2000 system data was introduced,mainly including float datum setting,residual static correction,phase-based moveout correction,which allows the imaging algorithms of conventional marine seismic data processing to extend to deep-towed seismic data.We successfully applied the Kuiyang-ST2000 system and methodology of data processing to a gas hydrate survey of the Qiongdongnan and Shenhu areas in the South China Sea,and the results show that the profile has very high vertical and lateral resolutions(0.5 m and 8 m,respectively),which can provide full and accurate details of gas hydrate-related and geohazard sedimentary and structural features in the South China Sea.
基金supported by the National Natural Science Foundation of China under grant no.42374133the Beijing Nova Program under grant no.2022056+1 种基金the Fundamental Research Funds for the Central Universities under grant no.2462020YXZZ006the Young Elite Scientists Sponsorship Program by CAST(YESS)under grant no.2018QNRC001。
文摘(Multichannel)Singular spectrum analysis is considered as one of the most effective methods for seismic incoherent noise suppression.It utilizes the low-rank feature of seismic signal and regards the noise suppression as a low-rank reconstruction problem.However,in some cases the seismic geophones receive some erratic disturbances and the amplitudes are dramatically larger than other receivers.The presence of this kind of noise,called erratic noise,makes singular spectrum analysis(SSA)reconstruction unstable and has undesirable effects on the final results.We robustify the low-rank reconstruction of seismic data by a reweighted damped SSA(RD-SSA)method.It incorporates the damped SSA,an improved version of SSA,into a reweighted framework.The damping operator is used to weaken the artificial disturbance introduced by the low-rank projection of both erratic and random noise.The central idea of the RD-SSA method is to iteratively approximate the observed data with the quadratic norm for the first iteration and the Tukeys bisquare norm for the rest iterations.The RD-SSA method can suppress seismic incoherent noise and keep the reconstruction process robust to the erratic disturbance.The feasibility of RD-SSA is validated via both synthetic and field data examples.
基金supported by the PetroChina Prospective,Basic,and Strategic Technology Research Project(No.2021DJ0606).
文摘There is little low-and-high frequency information on seismic data in seismic exploration,resulting in narrower bandwidth and lower seismic resolution.It considerably restricts the prediction accuracy of thin reservoirs and thin interbeds.This study proposes a novel method to constrain improving seismic resolution in the time and frequency domain.The expected wavelet spectrum is used in the frequency domain to broaden the seismic spectrum range and increase the octave.In the time domain,the Frobenius vector regularization of the Hessian matrix is used to constrain the horizontal continuity of the seismic data.It eff ectively protects the signal-to-noise ratio of seismic data while the longitudinal seismic resolution is improved.This method is applied to actual post-stack seismic data and pre-stack gathers dividedly.Without abolishing the phase characteristics of the original seismic data,the time resolution is signifi cantly improved,and the structural features are clearer.Compared with the traditional spectral simulation and deconvolution methods,the frequency distribution is more reasonable,and seismic data has higher resolution.
文摘A novel technique for automatic seismic data processing using both integral and local feature of seismograms was presented in this paper. Here, the term integral feature of seismograms refers to feature which may depict the shape of the whole seismograms. However, unlike some previous efforts which completely abandon the DIAL approach, i.e., signal detection, phase identifi- cation, association, and event localization, and seek to use envelope cross-correlation to detect seismic events directly, our technique keeps following the DIAL approach, but in addition to detect signals corresponding to individual seismic phases, it also detects continuous wave-trains and explores their feature for phase-type identification and signal association. More concrete ideas about how to define wave-trains and combine them with various detections, as well as how to measure and utilize their feature in the seismic data processing were expatiated in the paper. This approach has been applied to the routine data processing by us for years, and test results for a 16 days＇ period using data from the Xinjiang seismic station network were presented. The automatic processing results have fairly low false and missed event rate simultaneously, showing that the new technique has good application prospects for improvement of the automatic seismic data processing.
文摘A comprehensive study of the data profiles, including the 2D seismic data, single channel seismic data, shallow sections, etc., reveals that gas hydrates occur in the East China Sea. A series of special techniques are used in the processing of seismic data, which include enhancing the accuracy of velocity analysis and resolution, estimating the wavelet, suppressing the multiple, preserving the relative amplitude, using the DMO and AVO techniques and some special techniques in dealing with the wave impedance. The existence of gas hydrates is reflected in the subbottom profiles in the appearance of BSRs, amplitude anomalies, velocity anomalies and AVO anomalies, etc. Hence the gas hydrates can be identified and predicted. It is pointed out that the East China Sea is a favorable area of the gas hydrates resource, and the Okinawa Trough is a target area of gas hydrates reservoir.
文摘Branching river channels and the coexistence of valleys, ridges, hiils, and slopes＇as the result of long-term weathering and erosion form the unique loess topography. The Changqing Geophysical Company, working in these complex conditions, has established a suite of technologies for high-fidelity processing and fine interpretation of seismic data. This article introduces the processes involved in the data processing and interpretation and illustrates the results.
文摘The seismic reflection method is one of the most important methods in geophysical exploration.There are three stages in a seismic exploration survey:acquisition,processing,and interpretation.This paper focuses on a pre-processing tool,the Non-Local Means(NLM)filter algorithm,which is a powerful technique that can significantly suppress noise in seismic data.However,the domain of the NLM algorithm is the whole dataset and 3D seismic data being very large,often exceeding one terabyte(TB),it is impossible to store all the data in Random Access Memory(RAM).Furthermore,the NLM filter would require a considerably long runtime.These factors make a straightforward implementation of the NLM algorithm on real geophysical exploration data infeasible.This paper redesigned and implemented the NLM filter algorithm to fit the challenges of seismic exploration.The optimized implementation of the NLM filter is capable of processing production-size seismic data on modern clusters and is 87 times faster than the straightforward implementation of NLM.
文摘In this paper, multi-scaled morphology is introduced into the digital processing domain for land seismic data. First, we describe the basic theory of multi-scaled morphology image decomposition of exploration seismic waves; second, we illustrate how to use multi-scaled morphology for seismic data processing using two real examples. The first example demonstrates suppressing the surface waves in pre-stack seismic records using multi-scaled morphology decomposition and reconstitution and the other example demonstrates filtering different interference waves on the seismic record. Multi-scaled morphology filtering separates signal from noise by the detailed differences of the wave shapes. The successful applications suggest that multi-scaled morphology has a promising application in seismic data processing.
基金supported by the National Natural Science Foundation of China(41174084 and41474086)the CAS/CAFEA International Partnership Program for creative research teams(KZZD-EW-TZ-19)
文摘Subduction zones can generally be classified into Mariana type and Chilean type depending on plate ages, plate thicknesses, subduction angles, back-arc deformation patterns, etc. The double seismic zones （DSZs） in sub- duction zones are mainly divided into type I and type II which, respectively, correspond to the Mariana type and Chilean type in most cases. Seismic anisotropy is an important parameter characterizing the geophysical fea- tures of the lithosphere, including the subduction zones, and can be described by the two parameters of delay time ~t and fast wave polarization direction ~b. We totally col- lected 524 seismic anisotropy data records from 24 DSZs and analyzed the statistical correlations between seismic anisotropy and the related physical parameters of DSZs. Our statistical analysis demonstrated that the fast wave polarization directions are parallel to the trench strike with no more than 30~ for most type I DSZs, while being nearlyperpendicular to the trench strike for type II DSZs. We also calculated roughly linear correlations that the delay time 6t increases with dip angles but decreases with subduction rates. A linear equation was summarized to describe the strong correlation between DSZ＇s subduction angle DSZ and seismic anisotropy in subduction zones. These results suggest that the anisotropic structure of the subducting lithosphere can be described as a possible equivalent crystal similar to the olivine crystal with three mutually orthogonal polarization axes, of which the longest and the second axes are nearly along the trench-perpendicular and trench-parallel directions, respectively.
文摘Data processing is a basic and crucial factor in seismic exploration,which can influence the effect of subsequent processing directly. Thus the selection of appropriate method for data processing is one of the most important tasks throughout the work. By simulating,the authors analyze and compare Fractional Fourier Transform( FRFT) and Wigner-Ville distribution( WVD),then summarize the similarities and advantages and disadvantages of the two methods. The results reveal that FRFT is more effective and suitable for application in seismic exploration than WVD.
基金funded by the National Natural Science Foundation of China(Grant Nos.42241206,92058210,42074047,U2039203,42130306)。
文摘Recent geodetic and seismological observations of two major earthquakes in southeastern Türkiye in February 2023 have revealed complex rupture initiation,propagation,and segmentation along the East Anatolian Fault Zone(EAFZ)and surrounding regions.However,the role of upper crust structures along the EAFZ in determining the diverse rupture processes of this earthquake doublet remains unclear.To further investigate this,we employed double-difference location and seismic tomography techniques to determine high-resolution seismic velocities(V_(P),V_(S))and Poisson’s ratio(σ)structures using a multiparameter joint tomographic algorithm.Our dataset includes 100,833 high-quality source-receiver travel-time pairs of P-and Swaves.We find that the unique rupture processes of this earthquake doublet were primarily influenced by contrasting crustal seismic structures and localized geological settings.The M_(w)7.8 mainshock was initiated within a transitional edge zone characterized by a rigid part(asperity)of the seismogenic zone with sharp contrast variations in rock strength ranging from low to high along the EAFZ.In comparison,the M_(w)7.6 rupture originated in a ductile belt featuring fluid saturation with low-VP,low-VS,and high-σvalues that extended parallel to the Cardak Fault.The pronounced contrast structures observed along the former rupture can be attributed to the oblique collision system between the weakened section of the east Anatolian plateau and the brittle Arabian platform,while the latter rupture was initiated within the ductile structure associated with fluid intrusion caused by the northward subduction of the Cyprus slab and subsequent detachment.Furthermore,the occurrence of the first earthquake(E1)serves to alleviate shear stress on the second earthquake(E2)fault,potentially impeding the initiation of an E2 rupture.On the contrary,this event also significantly reduces the normal stress acting on the E2 fault due to a double left-lateral strike-slip system within a triangular region.This reduction not only results in a decrease of fault friction force and an increase in rock porosity but also induces lower strain drops and the redistribution of Coulomb stress,thereby contributing to the initiation of the E2 event.The proposed rupture pattern exceeds the conventional model that governs individual earthquake ruptures,offering new insights for mitigating potential seismic disasters in Türkiye.The lessons learned from this doublet event can contribute to reevaluating the ongoing risk of damaging earthquakes in China’s South-North Seismic Zone or other regions worldwide with comparable geological conditions.
文摘Attenuation of migration artifacts on Kirchhoff migrated seismic data can be challenging due to the relatively low amplitude of migration artifacts compared to reflections as well as the overlap in the kinematics of reflection and migration smiles.Several‘conventional’filtering methods exist and recently deep learning based workflows have been proposed.A deep learning workflow can be a simple and fast alternative to existing methods.In case of supervised training of a deep neural network using training data made by physics-based modelling or actual migrations is expensive and lacks diversity in terms of noise,amplitude,frequency content and wavelet.This can result in poor generalization beyond the training data without re-training and transfer learning.In this paper we demonstrate successful applications of migration smile separation using a conventional U-net architecture.The novelty in our approach is that we do not use synthetic data created from physics-based modelling,but instead use only synthetic data build form basic geometric shapes.Our domain of application is the migrated common offset domain,or simply the stack of the pre-stack migrated data,where reflections resemble local geology and migration smiles are upward convex hyperbolic patterns.Both patterns were randomly perturbed in many ways while maintaining their intrinsic features.This approach is inspired by the common practice of data augmentation in deep learning for machine vision applications.Since many of the standard data augmentation techniques lack a geophysical motivation,we have instead perturbed our synthetic training data in ways to make more sense for a signal processing perspective or given our‘domain knowledge’of the problem at hand.We did not have to retrain the network to produce good results on the field dataset.The large variety and diversity in examples enabled the trained neural network to show encouraging results on synthetic and field datasets that were not used in training.
文摘For thin gas reservoir of low-porosity and low-permeability in the loess desert area, a suite of lateral reservoir prediction techniques has been developed by Changqing Oil Company and the excellent effects achieved in exploration and exploitation in the areas such as Yulin, Wushenqi,Suligemiao, Shenmu etc., so that the Upper Paleozoic gas reserve has been stably increasing for eight years in Changqing Oilfield. The paper analyzed the effects and experience of the application of these techniques in detail.
基金supported by National Natural Science Foundation of China (41304046)
文摘On 25 April, 2015, an Mw7.9 earthquake occurred in Nepal, which caused great economic loss and casualties. However, almost no surface ruptures were observed. Therefore, in order to interpret the phenomenon, we study the rupture process of the earthquake to seek answers. Inversion of teleseismic body-wave data is applied to estimate the rupture process of the 2015 Nepal earthquake. To obtain stable solutions, smoothing and non-negative constraints are introduced. 48 teleseismic stations with good coverage are chosen. Finite fault model is established with length and width of 195 km and 150 km, and we set the initial seismic source parameters referring to CMT solutions. Inversion results indicate that the focal mechanism of this earthquake is a thrust fault type, and the strike, dip and rake angle are in accordance with CMT results. The seismic moment is 0.9195 ×10^（21）Nm（Mw7.9）, and source duration is about 70s. The rupture nucleated near the hypocenter and then propagated along the dip direction to the southeast, and the maximum slip amounts to 5.2 m. Uncertainties on the amount of slip retrieved by different inversion methods still exist, the overall characteristics are inconsistent. The lack of shallow slip during the 2015 Gorkha earthquake implies future seismic hazard and this region should be paid more attention to.
文摘The strong earthquakes in western Yunnan area, mainly occur along great interplate strike slip faults and have a dominant depth layer about 10～20 km; the seismic rupture is characterized by strike slip rupture. Considering the Yunnan lithospheric structure and dynamic background, we think that earthquakes occurring at this area might have such a kind of nucleation process: because of the multi layers and heterogeneities of lithospheric structure, a zone of concentrated shear strain or of slip might be formed at the moderate or deep portions of lithosphere, and spread upward along faulting boundary, toward the earths surface under the background field of tectonic movement of lithospheric plates. The slip front will encounter the maximum shear resistance zone on the fault surface in this process, be barried and blocked, and form a seismic gap. With the increase of tectonic load, this slip zone will continuously spread forward, traverse and lead to instable crack of the whole blocked zone, and cause a great earthquake. We have derived an approximate integral equation describing this seismic process; the numerical results show that the model has an instable nonlinear accelerating evolution period which might have important significance for the generation of earthquake precursors.
文摘The seismicity characteristics of the earthquake swarm occurred in Datong area in Shanxi Province during 1989-1993 period are studied in detail. The focal mechanisms and rupture processes of the principal earthquakes in itare also estimated in this paper. A mechanical model of fracture system of asymmetrical conjugate array is suggested from the view point of fracture propagation in order to simulate the mechanical features in the seismicsource respect of the Datong swarm sequence. The computation results of displacement field, stress field andstrain energy distribution from this model by using finite element method are presented. In addition, somerecorded data of geothermal precursors before these three climaxes of the Datong earthquake swarm sequence arediscussed mainly in this paper.
基金support by TOTAL/INRIA strategic action DIP(Depth Imaging Partnership).
文摘This work pertains to numerical aspects of a finite element method based discontinuous functions.Our study focuses on the Interior Penalty Discontinuous Galerkin method(IPDGM)because of its high-level of flexibility for solving the full wave equation in heterogeneousmedia.We assess the performance of IPDGMthrough a comparison study with a spectral element method(SEM).We show that IPDGM is as accurate as SEM.In addition,we illustrate the efficiency of IPDGM when employed in a seismic imaging process by considering two-dimensional problems involving the Reverse Time Migration.
