Total organic carbon (TOC) prediction with elastic parameter inversions has been widely used in the identification and evaluation of source rocks. However, the elastic parameters used to predict TOC are not only deter...Total organic carbon (TOC) prediction with elastic parameter inversions has been widely used in the identification and evaluation of source rocks. However, the elastic parameters used to predict TOC are not only determined by TOC but also depend on the other physical properties of source rocks. Besides, the TOC prediction with the elastic parameters inversion is an indirect method based on the statistical relationship obtained from well logs and experiment data. Therefore, we propose a rock physics model and define a TOC indicator mainly affected by TOC to predict TOC directly. The proposed rock physics model makes the equivalent elastic moduli of source rocks parameterized by the TOC indicator. Combining the equivalent elastic moduli of source rocks and Gray’s approximation leads to a novel linearized approximation of the P-wave reflection coefficient incorporating the TOC indicator. Model examples illustrate that the novel reflectivity approximation well agrees with the exact Zoeppritz equation until incident angles reach 40°. Convoluting the novel P-wave reflection approximation with seismic wavelets as the forward solver, an AVO inversion method based on the Bayesian theory is proposed to invert the TOC indicator with seismic data. The synthetic examples and field tests validate the feasibility and stability of the proposed AVO inversion approach. Using the inversion results of the TOC indicator, TOC is directly and accurately estimated in the target area.展开更多
Taiyuan formation is the main exploration strata in Ordos Basin, and coals are widely developed. Due to the interference of strong reflection of coals, we cannot completely identify the effective reservoir information...Taiyuan formation is the main exploration strata in Ordos Basin, and coals are widely developed. Due to the interference of strong reflection of coals, we cannot completely identify the effective reservoir information of coal-bearing reservoir on seismic data. Previous researchers have studied the reservoir by stripping or weakening the strong reflection, but it is difficult to determine the effectiveness of the remaining reflection seismic data. In this paper, through the establishment of 2D forward model of coal-bearing strata, the corresponding geophysical characteristics of different reflection types of coal-bearing strata are analyzed, and then the favorable sedimentary facies zones for reservoir development are predicted. On this basis, combined with seismic properties, the coal-bearing reservoir is quantitatively characterized by seismic inversion. The above research shows that the Taiyuan formation in LS block of Ordos Basin is affected by coals and forms three or two peaks in different locations. The reservoir plane sedimentary facies zone is effectively characterized by seismic reflection structure. Based on the characteristics of sedimentary facies belt and petrophysical analysis, the reservoir is semi quantitatively characterized by attribute analysis and waveform indication, and quantitatively characterized by pre stack geostatistical inversion. Based on the forward analysis of coal measure strata, this technology characterizes the reservoir facies belt through seismic reflection characteristics, and describes coal measure reservoirs step by step. It effectively guides the exploration of LS block in Ordos Basin, and has achieved good practical application effect.展开更多
The investigation of the tectonic deformation characteristics at the front margin of the Xu-Su arc tectonic belt provides important reference points for identifying and analyzing its genetic mechanism,tectonic evoluti...The investigation of the tectonic deformation characteristics at the front margin of the Xu-Su arc tectonic belt provides important reference points for identifying and analyzing its genetic mechanism,tectonic evolution process,and the latest evidence of tectonic deformation.In this study,two reflection seismic exploration profiles across the front margin of the Xu-Su arc tectonic belt are utilized to reveal that the Qinglongshan fault is the thrust fault of its front margin boundary.The kinematic properties and tectonic deformation characteristics of the internal faults in the front margin basin are also obtained.Using the Qinglongshan fault as the boundary,the middle and posterior margins of the Xu-Su arc tectonic belt are composed of numerous thrust faults,which suggest strong ancient tectonic movement.However,a large number of normal faults are developed within the front margin basin,with some faults exhibiting strike-slip and growth properties,which indicate strong neotectonic movement.Results reveal that the Xu-Su arc tectonic belt is a large-scale thrust-nappe structure that has undergone structural inversion.The Xu-Su arc tectonic belt experienced strong tectonic activity during the Middle Pleistocene,and the most recent tectonic deformation has extended into the front margin basin interior.展开更多
The Qiongdongnan Basin（QDNB） is situated in the extensional zone at the vertex of the V-shaped northwest sub-basin, non-volcanic northern margin of the South China Sea（SCS）. From north to south, the thickness of t...The Qiongdongnan Basin（QDNB） is situated in the extensional zone at the vertex of the V-shaped northwest sub-basin, non-volcanic northern margin of the South China Sea（SCS）. From north to south, the thickness of the continental lithosphere decreases from 22 km on the northern continental shelf to 17 km at the deepest area of the central depression. A sharp change on the crustal structure is of importance to hydrocarbon exploration yet the dynamic causes remain unknown. A comprehensive study including （1） interpretation of seismic profiles,（2） P-wave velocity data modeling, and （3） magnetic anomalies analysis reveals that there are some high-density intrusions along the lithospheric thinning belt. Chaotic reflections can be found in the southwest of the QDNB, with a low velocity（〈3.4 km/s）, while in the center and the east, the intensively deformed strata passing towards the diapir flanks and their high velocities（〉6 km/s） suggest the existence of igneous diapirs. Diapirism differentiation are primarily achieved through analysis of the contact relationship and the thickness variations in the surrounding strata. The first phase of diapirism along the Songnan low uplift occurred in the Late Mesozoic, and the second phase of diapirism in a form of subsequent gas movement remained active until the Late Quaternary. The distribution and the evolution of the diapirs would have major implications for post-rift emplacement.展开更多
The research on gas hydrate is one of the topics of general interest in the field of energy resource and environment. The South China Sea has favorable conditions for the occurrence and formation of gas hydrate. The p...The research on gas hydrate is one of the topics of general interest in the field of energy resource and environment. The South China Sea has favorable conditions for the occurrence and formation of gas hydrate. The presence of gas hydrate changes acoustic properties of the sedimentary strata and results in the occurrence of bottom simulating reflectors, which makes the multi-channel seismic investigation an important method to identify gas hydrates. First, the paper, based on results of seismic reflection imaging, analyzes the qualitative seismic reflection characteristics of sedimentary strata containing gas hydrate. Some key seismic imaging techniques are also discussed. Next, a pseudo-well is constructed to perform an impedance inversion to get the quantitative velocity structure of the strata since there is no well in the study area. Finally, the velocity field from geophysical inversion is integrated with the geochemical and geophysical data acquired on the Ocean Drilling Program 184 cruise. All information confirms the presence of gas hydrate and shows its spatial distribution.展开更多
The Yinchuan basin,located on the western margin of the Ordos block,has the characteristics of an active continental rift.A NW-striking deep seismic reflection profile across the center of Yinchuan basin precisely rev...The Yinchuan basin,located on the western margin of the Ordos block,has the characteristics of an active continental rift.A NW-striking deep seismic reflection profile across the center of Yinchuan basin precisely revealed the fine structure of the crust.The images showed that the crust in the Yinchuan basin was characterized by vertical stratifications along a detachment located at a two-way travel time(TWT)of 8.0 s.The most outstanding feature of this seismic profile was the almost flat Mohorovicˇic′discontinuity(Moho)and a high-reflection zone in the lower crust.This sub-horizontal Moho conflicts with the general assumption of an uplifted Moho under sedimentary basins and continental rifts,and may indicate the action of different processes at depth during the evolution of sedimentary basins or rifts.We present a possible interpretation of these deep processes and the sub-horizontal Moho.The high-reflection zone,which consists of sheets of high-density,mantlederived materials,may have compensated for crustal thinning in the Yinchuan basin,leading to the formation of a sub-horizontal Moho.These high-density materials may have been emplaced by underplating with mantlesourced magma.展开更多
The Sichuan basin is the main part of the middle-upper Yangtze block,which has been experienced a long-term tectonic evolution since Archean.The Yangtze block was regarded as a stable block until the collision with th...The Sichuan basin is the main part of the middle-upper Yangtze block,which has been experienced a long-term tectonic evolution since Archean.The Yangtze block was regarded as a stable block until the collision with the Cathaysia block in late Neoproterozoic.A new deep seismic reflection profile conducted in the eastern Sichuan fold belt(ESFB)discovered a serials of south-dipping reflectors shown from lower crust to the mantle imply a frozen subduction zone within the Yangtze block.In order to prove the speculation,we also obtain the middle-lower crustal gravity anomalies by removing the gravity anomalies induced by the sedimentary rocks and the mantle beneath the Moho,which shows the mid-lower crustal structure of the Sichuan basin can be divided into eastern and western parts.Combined with the geochronology and Aeromagnetic anomalies,we speculated the Yangtze block was amalgamated by the West Sichuan and East Sichuan blocks separated by the Huayin-Chongqing line.The frozen subduction zone subsequently shifted to a shear zone accommodated the lower crustal shortening when the decollement at the base of the Nanhua system functioned in the upper plate.展开更多
Physical properties of sea water,such as salinity,temperature,density and acoustic velocity,could be demarcated through degradation of energy caused by water absorption,attenuation and other factors.To overcome the ch...Physical properties of sea water,such as salinity,temperature,density and acoustic velocity,could be demarcated through degradation of energy caused by water absorption,attenuation and other factors.To overcome the challenging difficulties in the quick monitoring of these physical properties,we have explored the high resolution marine seismic survey to instantly characterize them.Based on the unique wavefield propagating in the sea water,we have developed a new approach to suppress the noise caused by the shallow sea water disturbance and obtain useful information for estimating the sea water structure.This approach improves seismic data with high signal-to-noise ratio and resolution.The seismic reflection imaging can map the sea water structure acoustically.Combined with the knowledge of local water body structure profile over years,the instant model for predicting the sea water properties could be built using the seismic data acquired from the specially designed high precision marine seismic acquisition.This model can also be updated with instant observation and the complete data processing system.The present study has the potential value to many applications,such as 3D sea water monitoring,engineering evaluation,geological disaster assessment and environmental assessment.展开更多
Statics are big challenges for the processing of deep reflection seismic data. In this paper several different statics solutions have been implemented in the processing of deep reflection seismic data in South China a...Statics are big challenges for the processing of deep reflection seismic data. In this paper several different statics solutions have been implemented in the processing of deep reflection seismic data in South China and their corresponding results have been compared in order to find proper statics solutions. Either statics solutions based on tomographic principle or combining the low-frequency components of field statics with the high-frequency ones of refraction statics can provide reasonable statics solutions for deep reflection seismic data in South China with very rugged surface topography, and the two statics solutions can correct the statics anomalies of both long spatial wavelengths and short ones. The surface-consistent residual static corrections can serve as the good compensations to the several kinds of the first statics solutions. Proper statics solutions can improve both qualities and reso- lutions of seismic sections, especially for the reflections of Moho in the upmost mantle.展开更多
Recent studies have demonstrated the ability of seismic oceanography to reveal finescale vertical structures of water column in the oceans based on multichannel seismic(MCS)reflection data.Such information can clarify...Recent studies have demonstrated the ability of seismic oceanography to reveal finescale vertical structures of water column in the oceans based on multichannel seismic(MCS)reflection data.Such information can clarify the dynamic processes of mixing,exchange,and translation of water mass and energy.In this study,we present four MCS lines and satellite data to show high-resolution seismic images of shallow waters over the Shatsky Rise in the Northwest Pacific Ocean,where the Kuroshio Exten-sion passes and bifurcates.One of our MCS transects crossed the center of an anticyclonic warm eddy on August 28,2010,confirmed by satellite data such as sea level anomaly(SLA),geostrophic current anomaly(GCA),and sea surface temperature anomaly(SSTa).The seismic image showed that the eddy vertical structure featured a bowl-like shape and onion-like internal layering.The slightly tilted(<0.5°)surface of the eddy was 400m below the sea surface,indicating a subsurface eddy.The eddy was inferred to have a radius of 50 km and a maximum thickness of 500m.Other MCS sections demonstrated the submesoscale structure of oceanfronts,characterized by the dipping reflectors(>2°-3°)at the boundaries between water masses with differing properties.In addition,the discrepancies in SLA,GCA,and SSTa between water masses resulted in different seismic reflectivities.The water masses with high SLA,anticyclonic GCA and positive SSTa featured high-amplitude,continuous,clear-layered,and non-linear reflections,whereas those with low SLA,cyclonic GCA,and negative SSTa were associated with weak,fragmented,less stratification,and more linear reflectors.展开更多
Research into the contourite deposits in the Upper Meishan Formation of the southern Qiongdongnan Basin in South China Sea is weak;their characteristics,distribution and original geological conditions are not clear.Us...Research into the contourite deposits in the Upper Meishan Formation of the southern Qiongdongnan Basin in South China Sea is weak;their characteristics,distribution and original geological conditions are not clear.Using geologic al and geophysical methods including seismic and drilling data,based on seismic reflection characteristics,geometrical configuration description,and wave impedance inversion,two types of contourite deposits are recognized.Contourite deposits have blurred boundaries between each deposit and disordered internal seismic reflections;They are mound-shaped only in transverse section,and banded in the longitudinal direction.TypeⅠcontourite deposits are conical,with mediumhigh amplitude,low-continuity,low-frequency mound-shaped seismic facies,and subparallel-chaotic reflections internally.These deposits are conical with sharp tops,the canal between mounds is V-shaped and deep.The western wing is gentle and the eastern wing is steep,with the slope toe mostly between 10°and 20°,and width height ratio about 1-2.TypeⅡcontourite deposits are flat,exhibiting medium-amplitude,medium-continuity,low-frequency mound-shaped seismic facies,with subparallel weak reflections internally.Their mounds are flat with gently arced tops,with shallow canals between.The slope toe is between 5°and 10°,with a width height ratio of about 2-5.The wave impedance value of these contourite deposits is 4.6 kg/m^(3)×m/s to 6.8 kg/m^(3)×m/s,about 5.8 kg/m^(3)×m/s on average,which is presumed to represent marlycalcareous clastic sediments.The contourite deposits mainly develop beneath the slope break at the margin of the faultcontrolled platform in the Southern Uplift zone of the basin.In plane view,they are distributed approaching a west-to-east direction,and in section,lie in low-lying areas near the faults at fault-controlled terraces of the Southern Uplift zone,with a paleo-current direction nearly west-to-east.The paleotectonic setting of the gentle monoclinic platform was favorable for the development of such contourite deposits.The intensification of the Mid-Miocene deepest bottom current gave rise to the contourite-forming currents around the Southern Uplift zone in the northern South China Sea,which flow from Hainan Island to the Xisha Trough in a nearly west-to-east direction leading to the contourite deposits developing in the late MidMiocene transgressive environment,with multiple slow sea-level fall cycles.展开更多
Seismic wave modeling is a cornerstone of geophysical data acquisition, processing, and interpretation, for which finite-difference methods are often applied. In this paper, we extend the velocity- pressure formulatio...Seismic wave modeling is a cornerstone of geophysical data acquisition, processing, and interpretation, for which finite-difference methods are often applied. In this paper, we extend the velocity- pressure formulation of the acoustic wave equation to marine seismic modeling using the staggered-grid finite-difference method. The scheme is developed using a fourth-order spatial and a second-order temporal operator. Then, we define a stability coefficient (SC) and calculate its maximum value under the stability condition. Based on the dispersion relationship, we conduct a detailed dispersion analysis for submarine sediments in terms of the phase and group velocity over a range of angles, stability coefficients, and orders. We also compare the numerical solution with the exact solution for a P-wave line source in a homogeneous submarine model. Additionally, the numerical results determined by a Marmousi2 model with a rugged seafloor indicate that this method is sufficient for modeling complex submarine structures.展开更多
The existing seismic reflection pattern classification methods need to convert multidimensional prestack seismic data into one-dimensional vectors for processing,which loses the characteristics of amplitude variation ...The existing seismic reflection pattern classification methods need to convert multidimensional prestack seismic data into one-dimensional vectors for processing,which loses the characteristics of amplitude variation with offset/azimuth in the prestack seismic data.In this study,a tensor discriminant dictionary learning method for classifying prestack seismic reflection patterns is proposed.The method is initially based on the tensor Tucker decomposition algorithm and uses a tensor form to characterize the prestack seismic data with multidimensional features.The tensor discriminant dictionary is then used to reduce the influence of noise on the sample features.Finally,the method uses the Pearson correlation coefficient to measure the correlation degree of the sparse representation coefficients of different types of tensors.The advantages of the new method are as follows.(1)It can retain the rich structural features in different dimensions in the prestack data.(2)It adjusts the threshold of the Pearson correlation coefficient to optimize the classification effect.(3)It fully uses drilling information and expert knowledge and performs calibration training of the sample labels.The numerical-model tests confirm that the new method is more accurate and robust than the traditional support vector machine and K-nearest neighbor classification algorithms.The application of actual data further confirms that the classification results of the new method agree with the geological patterns and are more suitable for the analysis and interpretation of sedimentary facies.展开更多
Shallow shear-wave seismic reflection imaging, using a sledgehammer and mass energy source and standard processing, has become increasingly common in mapping near-surface geologic features, especially in water-saturat...Shallow shear-wave seismic reflection imaging, using a sledgehammer and mass energy source and standard processing, has become increasingly common in mapping near-surface geologic features, especially in water-saturated, unconsolidated sediments. Tests of the method in the Mississippi Embayment region of the central United States show interpretable reflection arrivals in the depth range of 〈10 m to 〉100 m with the potential for increased resolution when compared with compressional-wave data. Shear-wave reflection prof＇des were used to help interpret the significance of neotectonic surface deformation at five sites in the Mississippi Embayment. The interpreted profiles show a range of shallow structural styles that include reverse faulting, fault propagation folding, and reactivated normal faulting, and provide crucial subsurface evidence in support of paleoseismologic trenching and shallow drilling.展开更多
Through discussion of the time-distance curve characteristics of the direct waveand from the front,side and rear of the reflection waves of the seismic reflection methodfor advanced exploration in mines,and analysis o...Through discussion of the time-distance curve characteristics of the direct waveand from the front,side and rear of the reflection waves of the seismic reflection methodfor advanced exploration in mines,and analysis of several major interference waves inmines,the differences in time-distance curve,frequency,apparent velocity between theeffective wave and interference wave in the seismic reflection method for advanced explorationare obtained.According to the differences,the effective wave is extracted andthe interference wave is filtered and the system's precision and accuracy is improved.展开更多
Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-refl...Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-reflection result. Based on the data of complete Bouguer gravity anomaly and seismic reflection, we obtained a layered interface structure in deep crust down to Moho. Our study showed that the inversion could reveal the interfaces of strata along the survey profile and the directions of regional faults in two-dimension. From the characteristics of the observed topography of the Moho basement, we tentatively confirmed that the uplift of eastern edge of Qinghai-Tibet plateau was caused by the subduetion of the Indian plate.展开更多
More than 4 000 km 48-channel seismic reflection data from the central region of the South China Sea have been interpreted. Five seismic interfaces have been distinguished, named T1, T2, T4, T6 and Tg respectively Mea...More than 4 000 km 48-channel seismic reflection data from the central region of the South China Sea have been interpreted. Five seismic interfaces have been distinguished, named T1, T2, T4, T6 and Tg respectively Meanwhile, five seismic sequences numbered I - V have been divided with the ages of Quaternary and Pliocene, Later Mocene, Earlier and Middle Miocene, Oligocene and Pre- Oligocene separately. Sequences I-II overlie all parts of the area. In the continental slope and island slope, Sequences III-V are mainly found in the grabens. Sequence III is found at moot profiles of the deep-sea basin, and Sequnce IV is seen not only at the margins of the east subbasin but also at the margins of the southwest subbasin. Strong reflection from Moho is found at most profiles of the deep-sea basin. The depth of Moho varies between 10 and 12 km, with a thickness of 6- 8 km for the crust. Calculated by age-basement depth correlation formula, the age of basaltic basement in the southwest subbasin is 51-39 Ma. It is indicated that the evolution of the southwest subbasin is simultaneous with or earlier than that of the east subbasin.展开更多
The Qinling orogen was formed as a result of the collision between the North and South China blocks. The Qinling orogen represents the location at which the southern and northern parts of the Chinese mainland col- lid...The Qinling orogen was formed as a result of the collision between the North and South China blocks. The Qinling orogen represents the location at which the southern and northern parts of the Chinese mainland col- lided, and it＇s also the intersection of the Central China orogen and the north-south tectonic belt. There is evidence of strong deformation in this orogen, and it has had a long and complex geological history. We investigated the structure of the Moho in the southern Qinling orogen using large dynamite shot imaging techniques. By integrating the analysis of the single-shot and the move-out corrections profile, we determined the structure of the Moho beneath the northern Dabashan thrust belt and the southern Qinling orogen, including the mantle suture beneath Fenghuang mountain. The Moho is divided into two parts by the mantle suture zone beneath Fenghuang mountain： （1） from Ziyang to Hanyin, the north-dipping Moho is at about 45-55 km depth and the depth increases rapidly; and （2） from Hanyin to Ningshan, the south-dipping Moho is at about 40-45 km depth and shallows slowly. The mantle suture is located beneath Fenghuang mountain, and the Moho overlaps at this location： the shallower Moho is connected to the northern part of China, and the deeper Moho is connected to the southern part. This may indicate that the lithosphere in the Sichuan basin subducts to the Qinling block and that the subduction frontier reaches at least as far as Fenghuang mountain.展开更多
The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 5...The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.展开更多
Seismic wave reflection method is an advanced geophysical detection method in tunnel geological prediction.It is more sensitive and effective in detecting geological anomalies such as fault fracture zone and karst.In ...Seismic wave reflection method is an advanced geophysical detection method in tunnel geological prediction.It is more sensitive and effective in detecting geological anomalies such as fault fracture zone and karst.In order to verify the prediction efficacy and accuracy of the seismic wave reflection method with different instruments and equipment(tunnel geological prediction[TGP]/tunnel seismic prediction[TSP])and different vibration modes(hammering,explosives),a comparison test was carried out in Jinping Tunnel.The test results showed that the time-consumption of the hammering source was short,which can greatly reduce the impact on the construction site;different vibration sources methods of seismic wave reflection can predict the unfavorable geological sections accurately.展开更多
基金The authors acknowledge the sponsorship of National Natural Science Foundation of China(42174139,41974119,42030103)Laoshan Laboratory Science and Technology Innovation Program(LSKj202203406)Science Foundation from Innovation and Technology Support Program for Young Scientists in Colleges of Shandong Province and Ministry of Science and Technology of China(2019RA2136).
文摘Total organic carbon (TOC) prediction with elastic parameter inversions has been widely used in the identification and evaluation of source rocks. However, the elastic parameters used to predict TOC are not only determined by TOC but also depend on the other physical properties of source rocks. Besides, the TOC prediction with the elastic parameters inversion is an indirect method based on the statistical relationship obtained from well logs and experiment data. Therefore, we propose a rock physics model and define a TOC indicator mainly affected by TOC to predict TOC directly. The proposed rock physics model makes the equivalent elastic moduli of source rocks parameterized by the TOC indicator. Combining the equivalent elastic moduli of source rocks and Gray’s approximation leads to a novel linearized approximation of the P-wave reflection coefficient incorporating the TOC indicator. Model examples illustrate that the novel reflectivity approximation well agrees with the exact Zoeppritz equation until incident angles reach 40°. Convoluting the novel P-wave reflection approximation with seismic wavelets as the forward solver, an AVO inversion method based on the Bayesian theory is proposed to invert the TOC indicator with seismic data. The synthetic examples and field tests validate the feasibility and stability of the proposed AVO inversion approach. Using the inversion results of the TOC indicator, TOC is directly and accurately estimated in the target area.
文摘Taiyuan formation is the main exploration strata in Ordos Basin, and coals are widely developed. Due to the interference of strong reflection of coals, we cannot completely identify the effective reservoir information of coal-bearing reservoir on seismic data. Previous researchers have studied the reservoir by stripping or weakening the strong reflection, but it is difficult to determine the effectiveness of the remaining reflection seismic data. In this paper, through the establishment of 2D forward model of coal-bearing strata, the corresponding geophysical characteristics of different reflection types of coal-bearing strata are analyzed, and then the favorable sedimentary facies zones for reservoir development are predicted. On this basis, combined with seismic properties, the coal-bearing reservoir is quantitatively characterized by seismic inversion. The above research shows that the Taiyuan formation in LS block of Ordos Basin is affected by coals and forms three or two peaks in different locations. The reservoir plane sedimentary facies zone is effectively characterized by seismic reflection structure. Based on the characteristics of sedimentary facies belt and petrophysical analysis, the reservoir is semi quantitatively characterized by attribute analysis and waveform indication, and quantitatively characterized by pre stack geostatistical inversion. Based on the forward analysis of coal measure strata, this technology characterizes the reservoir facies belt through seismic reflection characteristics, and describes coal measure reservoirs step by step. It effectively guides the exploration of LS block in Ordos Basin, and has achieved good practical application effect.
基金The active fault exploration and seismic risk assessment project of Huaibei and the research and development project of Beijing Disaster Prevention Technology Co.,Ltd.(FZKJYF202201)jointly funded this work。
文摘The investigation of the tectonic deformation characteristics at the front margin of the Xu-Su arc tectonic belt provides important reference points for identifying and analyzing its genetic mechanism,tectonic evolution process,and the latest evidence of tectonic deformation.In this study,two reflection seismic exploration profiles across the front margin of the Xu-Su arc tectonic belt are utilized to reveal that the Qinglongshan fault is the thrust fault of its front margin boundary.The kinematic properties and tectonic deformation characteristics of the internal faults in the front margin basin are also obtained.Using the Qinglongshan fault as the boundary,the middle and posterior margins of the Xu-Su arc tectonic belt are composed of numerous thrust faults,which suggest strong ancient tectonic movement.However,a large number of normal faults are developed within the front margin basin,with some faults exhibiting strike-slip and growth properties,which indicate strong neotectonic movement.Results reveal that the Xu-Su arc tectonic belt is a large-scale thrust-nappe structure that has undergone structural inversion.The Xu-Su arc tectonic belt experienced strong tectonic activity during the Middle Pleistocene,and the most recent tectonic deformation has extended into the front margin basin interior.
基金supported by the National Natural Science Foundation of China (No. 41272121)the Major National Science and Technology Programs in the "Twelfth Five-Year" Plan of China (No. 2011ZX05025-002-02-02)the Fundamental Research Funds for the Central Universities (No. 16CX02038A)
文摘The Qiongdongnan Basin（QDNB） is situated in the extensional zone at the vertex of the V-shaped northwest sub-basin, non-volcanic northern margin of the South China Sea（SCS）. From north to south, the thickness of the continental lithosphere decreases from 22 km on the northern continental shelf to 17 km at the deepest area of the central depression. A sharp change on the crustal structure is of importance to hydrocarbon exploration yet the dynamic causes remain unknown. A comprehensive study including （1） interpretation of seismic profiles,（2） P-wave velocity data modeling, and （3） magnetic anomalies analysis reveals that there are some high-density intrusions along the lithospheric thinning belt. Chaotic reflections can be found in the southwest of the QDNB, with a low velocity（〈3.4 km/s）, while in the center and the east, the intensively deformed strata passing towards the diapir flanks and their high velocities（〉6 km/s） suggest the existence of igneous diapirs. Diapirism differentiation are primarily achieved through analysis of the contact relationship and the thickness variations in the surrounding strata. The first phase of diapirism along the Songnan low uplift occurred in the Late Mesozoic, and the second phase of diapirism in a form of subsequent gas movement remained active until the Late Quaternary. The distribution and the evolution of the diapirs would have major implications for post-rift emplacement.
基金The research was supported by Hi-tech Research and Development Program of China (2003AA611020-01).
文摘The research on gas hydrate is one of the topics of general interest in the field of energy resource and environment. The South China Sea has favorable conditions for the occurrence and formation of gas hydrate. The presence of gas hydrate changes acoustic properties of the sedimentary strata and results in the occurrence of bottom simulating reflectors, which makes the multi-channel seismic investigation an important method to identify gas hydrates. First, the paper, based on results of seismic reflection imaging, analyzes the qualitative seismic reflection characteristics of sedimentary strata containing gas hydrate. Some key seismic imaging techniques are also discussed. Next, a pseudo-well is constructed to perform an impedance inversion to get the quantitative velocity structure of the strata since there is no well in the study area. Finally, the velocity field from geophysical inversion is integrated with the geochemical and geophysical data acquired on the Ocean Drilling Program 184 cruise. All information confirms the presence of gas hydrate and shows its spatial distribution.
基金This study was financed jointly by the Sino Probe Project of China(Sinoprobe-02-01)the National Natural Science Foundation of China(Nos.41430213,41274097,and 41404072)+1 种基金Geological Investigation Project of China Geological Survey(Nos.1212011220260 and 12120115027101)“Urban Active Fault Detection”of National Development and Reform Commission(No.20041138)
文摘The Yinchuan basin,located on the western margin of the Ordos block,has the characteristics of an active continental rift.A NW-striking deep seismic reflection profile across the center of Yinchuan basin precisely revealed the fine structure of the crust.The images showed that the crust in the Yinchuan basin was characterized by vertical stratifications along a detachment located at a two-way travel time(TWT)of 8.0 s.The most outstanding feature of this seismic profile was the almost flat Mohorovicˇic′discontinuity(Moho)and a high-reflection zone in the lower crust.This sub-horizontal Moho conflicts with the general assumption of an uplifted Moho under sedimentary basins and continental rifts,and may indicate the action of different processes at depth during the evolution of sedimentary basins or rifts.We present a possible interpretation of these deep processes and the sub-horizontal Moho.The high-reflection zone,which consists of sheets of high-density,mantlederived materials,may have compensated for crustal thinning in the Yinchuan basin,leading to the formation of a sub-horizontal Moho.These high-density materials may have been emplaced by underplating with mantlesourced magma.
基金the National Natural Science Foundation of China(Nos.41104056,41374093,40974060,41574093)basic scientific research fund of IG,CAGS(J1119)
文摘The Sichuan basin is the main part of the middle-upper Yangtze block,which has been experienced a long-term tectonic evolution since Archean.The Yangtze block was regarded as a stable block until the collision with the Cathaysia block in late Neoproterozoic.A new deep seismic reflection profile conducted in the eastern Sichuan fold belt(ESFB)discovered a serials of south-dipping reflectors shown from lower crust to the mantle imply a frozen subduction zone within the Yangtze block.In order to prove the speculation,we also obtain the middle-lower crustal gravity anomalies by removing the gravity anomalies induced by the sedimentary rocks and the mantle beneath the Moho,which shows the mid-lower crustal structure of the Sichuan basin can be divided into eastern and western parts.Combined with the geochronology and Aeromagnetic anomalies,we speculated the Yangtze block was amalgamated by the West Sichuan and East Sichuan blocks separated by the Huayin-Chongqing line.The frozen subduction zone subsequently shifted to a shear zone accommodated the lower crustal shortening when the decollement at the base of the Nanhua system functioned in the upper plate.
基金the Natural Science Foundation of China(41176077)Subject of 973(2009CB219505)+2 种基金Natural Science Foundation of Shandong(ZR2010DM012)Basic Research Special Foundation of the Third Institute of Oceanography affiliated to the State Oceanic Administration(TIOSOA,2009004)the Science Research Project for the South China Sea of Ocean University of China for their financial support to this work
文摘Physical properties of sea water,such as salinity,temperature,density and acoustic velocity,could be demarcated through degradation of energy caused by water absorption,attenuation and other factors.To overcome the challenging difficulties in the quick monitoring of these physical properties,we have explored the high resolution marine seismic survey to instantly characterize them.Based on the unique wavefield propagating in the sea water,we have developed a new approach to suppress the noise caused by the shallow sea water disturbance and obtain useful information for estimating the sea water structure.This approach improves seismic data with high signal-to-noise ratio and resolution.The seismic reflection imaging can map the sea water structure acoustically.Combined with the knowledge of local water body structure profile over years,the instant model for predicting the sea water properties could be built using the seismic data acquired from the specially designed high precision marine seismic acquisition.This model can also be updated with instant observation and the complete data processing system.The present study has the potential value to many applications,such as 3D sea water monitoring,engineering evaluation,geological disaster assessment and environmental assessment.
基金supported by the Foundation of Institute of Geology,Chinese Academy of Geological Sciences (No. J1315)the 3D Geological Mapping Project (No. D1204)the SinoProbe-02 project of China
文摘Statics are big challenges for the processing of deep reflection seismic data. In this paper several different statics solutions have been implemented in the processing of deep reflection seismic data in South China and their corresponding results have been compared in order to find proper statics solutions. Either statics solutions based on tomographic principle or combining the low-frequency components of field statics with the high-frequency ones of refraction statics can provide reasonable statics solutions for deep reflection seismic data in South China with very rugged surface topography, and the two statics solutions can correct the statics anomalies of both long spatial wavelengths and short ones. The surface-consistent residual static corrections can serve as the good compensations to the several kinds of the first statics solutions. Proper statics solutions can improve both qualities and reso- lutions of seismic sections, especially for the reflections of Moho in the upmost mantle.
基金This research was supported by the National Key R&D Program of China(No.2018YFC0309800)the Guangdong Basic and Applied Basic Research Foundation(No.2021B1515020098)+3 种基金the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0205)the National Natural Science Foundation of China(Nos.41776058 and 41890813)the Chinese Academy of Sciences(Nos.133244KYSB20180029,131551KYSB20200021,Y4SL021001,QYZDY-SSW-DQC005 and ISEE 2019ZR01)the Laboratory for Marine Mineral Re-sources,Qingdao National Laboratory for Marine Sci-ence and Technology(No.MMRZZ201801).
文摘Recent studies have demonstrated the ability of seismic oceanography to reveal finescale vertical structures of water column in the oceans based on multichannel seismic(MCS)reflection data.Such information can clarify the dynamic processes of mixing,exchange,and translation of water mass and energy.In this study,we present four MCS lines and satellite data to show high-resolution seismic images of shallow waters over the Shatsky Rise in the Northwest Pacific Ocean,where the Kuroshio Exten-sion passes and bifurcates.One of our MCS transects crossed the center of an anticyclonic warm eddy on August 28,2010,confirmed by satellite data such as sea level anomaly(SLA),geostrophic current anomaly(GCA),and sea surface temperature anomaly(SSTa).The seismic image showed that the eddy vertical structure featured a bowl-like shape and onion-like internal layering.The slightly tilted(<0.5°)surface of the eddy was 400m below the sea surface,indicating a subsurface eddy.The eddy was inferred to have a radius of 50 km and a maximum thickness of 500m.Other MCS sections demonstrated the submesoscale structure of oceanfronts,characterized by the dipping reflectors(>2°-3°)at the boundaries between water masses with differing properties.In addition,the discrepancies in SLA,GCA,and SSTa between water masses resulted in different seismic reflectivities.The water masses with high SLA,anticyclonic GCA and positive SSTa featured high-amplitude,continuous,clear-layered,and non-linear reflections,whereas those with low SLA,cyclonic GCA,and negative SSTa were associated with weak,fragmented,less stratification,and more linear reflectors.
基金supported by the National Natural Science Foundation of China(grant no.41972155)the Jiangxi Provincial Natural Science Foundtion(grant no.2020BABL211019)the National Science and Technology Major Profect(grant no.2016ZX05026007)。
文摘Research into the contourite deposits in the Upper Meishan Formation of the southern Qiongdongnan Basin in South China Sea is weak;their characteristics,distribution and original geological conditions are not clear.Using geologic al and geophysical methods including seismic and drilling data,based on seismic reflection characteristics,geometrical configuration description,and wave impedance inversion,two types of contourite deposits are recognized.Contourite deposits have blurred boundaries between each deposit and disordered internal seismic reflections;They are mound-shaped only in transverse section,and banded in the longitudinal direction.TypeⅠcontourite deposits are conical,with mediumhigh amplitude,low-continuity,low-frequency mound-shaped seismic facies,and subparallel-chaotic reflections internally.These deposits are conical with sharp tops,the canal between mounds is V-shaped and deep.The western wing is gentle and the eastern wing is steep,with the slope toe mostly between 10°and 20°,and width height ratio about 1-2.TypeⅡcontourite deposits are flat,exhibiting medium-amplitude,medium-continuity,low-frequency mound-shaped seismic facies,with subparallel weak reflections internally.Their mounds are flat with gently arced tops,with shallow canals between.The slope toe is between 5°and 10°,with a width height ratio of about 2-5.The wave impedance value of these contourite deposits is 4.6 kg/m^(3)×m/s to 6.8 kg/m^(3)×m/s,about 5.8 kg/m^(3)×m/s on average,which is presumed to represent marlycalcareous clastic sediments.The contourite deposits mainly develop beneath the slope break at the margin of the faultcontrolled platform in the Southern Uplift zone of the basin.In plane view,they are distributed approaching a west-to-east direction,and in section,lie in low-lying areas near the faults at fault-controlled terraces of the Southern Uplift zone,with a paleo-current direction nearly west-to-east.The paleotectonic setting of the gentle monoclinic platform was favorable for the development of such contourite deposits.The intensification of the Mid-Miocene deepest bottom current gave rise to the contourite-forming currents around the Southern Uplift zone in the northern South China Sea,which flow from Hainan Island to the Xisha Trough in a nearly west-to-east direction leading to the contourite deposits developing in the late MidMiocene transgressive environment,with multiple slow sea-level fall cycles.
基金Supported by the National Natural Science Foundation of China(Nos. 41206043, 40930845)the Open Foundation of Key Laboratory of Marine Geology and Environment of Chinese Academy of Sciences(No. MGE2011KG07)+1 种基金the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-229)the National Basic Research Program of China (973 Program) (No. 2009CB219505)
文摘Seismic wave modeling is a cornerstone of geophysical data acquisition, processing, and interpretation, for which finite-difference methods are often applied. In this paper, we extend the velocity- pressure formulation of the acoustic wave equation to marine seismic modeling using the staggered-grid finite-difference method. The scheme is developed using a fourth-order spatial and a second-order temporal operator. Then, we define a stability coefficient (SC) and calculate its maximum value under the stability condition. Based on the dispersion relationship, we conduct a detailed dispersion analysis for submarine sediments in terms of the phase and group velocity over a range of angles, stability coefficients, and orders. We also compare the numerical solution with the exact solution for a P-wave line source in a homogeneous submarine model. Additionally, the numerical results determined by a Marmousi2 model with a rugged seafloor indicate that this method is sufficient for modeling complex submarine structures.
基金supported by the National Natural Science Foundation of China(Nos.42130812,42174151,and 41874155).
文摘The existing seismic reflection pattern classification methods need to convert multidimensional prestack seismic data into one-dimensional vectors for processing,which loses the characteristics of amplitude variation with offset/azimuth in the prestack seismic data.In this study,a tensor discriminant dictionary learning method for classifying prestack seismic reflection patterns is proposed.The method is initially based on the tensor Tucker decomposition algorithm and uses a tensor form to characterize the prestack seismic data with multidimensional features.The tensor discriminant dictionary is then used to reduce the influence of noise on the sample features.Finally,the method uses the Pearson correlation coefficient to measure the correlation degree of the sparse representation coefficients of different types of tensors.The advantages of the new method are as follows.(1)It can retain the rich structural features in different dimensions in the prestack data.(2)It adjusts the threshold of the Pearson correlation coefficient to optimize the classification effect.(3)It fully uses drilling information and expert knowledge and performs calibration training of the sample labels.The numerical-model tests confirm that the new method is more accurate and robust than the traditional support vector machine and K-nearest neighbor classification algorithms.The application of actual data further confirms that the classification results of the new method agree with the geological patterns and are more suitable for the analysis and interpretation of sedimentary facies.
基金supported by the U.S. Geological Survey, Department of the Interior
文摘Shallow shear-wave seismic reflection imaging, using a sledgehammer and mass energy source and standard processing, has become increasingly common in mapping near-surface geologic features, especially in water-saturated, unconsolidated sediments. Tests of the method in the Mississippi Embayment region of the central United States show interpretable reflection arrivals in the depth range of 〈10 m to 〉100 m with the potential for increased resolution when compared with compressional-wave data. Shear-wave reflection prof＇des were used to help interpret the significance of neotectonic surface deformation at five sites in the Mississippi Embayment. The interpreted profiles show a range of shallow structural styles that include reverse faulting, fault propagation folding, and reactivated normal faulting, and provide crucial subsurface evidence in support of paleoseismologic trenching and shallow drilling.
基金Supported by the National Natural Science Foundation of China(50375026)the National Basic Research Program of China(2005cb221500)+1 种基金the National Key Technology R&D Program(2006BAK03B01)the National Natural Science Foundation Key Program(50534080)
文摘Through discussion of the time-distance curve characteristics of the direct waveand from the front,side and rear of the reflection waves of the seismic reflection methodfor advanced exploration in mines,and analysis of several major interference waves inmines,the differences in time-distance curve,frequency,apparent velocity between theeffective wave and interference wave in the seismic reflection method for advanced explorationare obtained.According to the differences,the effective wave is extracted andthe interference wave is filtered and the system's precision and accuracy is improved.
基金supported by the Key Foundation of Institute of Seismology,China Earthquake Administration( IS200916004)
文摘Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-reflection result. Based on the data of complete Bouguer gravity anomaly and seismic reflection, we obtained a layered interface structure in deep crust down to Moho. Our study showed that the inversion could reveal the interfaces of strata along the survey profile and the directions of regional faults in two-dimension. From the characteristics of the observed topography of the Moho basement, we tentatively confirmed that the uplift of eastern edge of Qinghai-Tibet plateau was caused by the subduetion of the Indian plate.
文摘More than 4 000 km 48-channel seismic reflection data from the central region of the South China Sea have been interpreted. Five seismic interfaces have been distinguished, named T1, T2, T4, T6 and Tg respectively Meanwhile, five seismic sequences numbered I - V have been divided with the ages of Quaternary and Pliocene, Later Mocene, Earlier and Middle Miocene, Oligocene and Pre- Oligocene separately. Sequences I-II overlie all parts of the area. In the continental slope and island slope, Sequences III-V are mainly found in the grabens. Sequence III is found at moot profiles of the deep-sea basin, and Sequnce IV is seen not only at the margins of the east subbasin but also at the margins of the southwest subbasin. Strong reflection from Moho is found at most profiles of the deep-sea basin. The depth of Moho varies between 10 and 12 km, with a thickness of 6- 8 km for the crust. Calculated by age-basement depth correlation formula, the age of basaltic basement in the southwest subbasin is 51-39 Ma. It is indicated that the evolution of the southwest subbasin is simultaneous with or earlier than that of the east subbasin.
基金funded by basic research funds of the Chinese Academy of Geological Sciences (J1628)the National Natural Science Foundation of China (Nos.441590863 and 41430213)+1 种基金the Ministry of Land and Resources of China (Nos.201311159Sino Probe-02-01)
文摘The Qinling orogen was formed as a result of the collision between the North and South China blocks. The Qinling orogen represents the location at which the southern and northern parts of the Chinese mainland col- lided, and it＇s also the intersection of the Central China orogen and the north-south tectonic belt. There is evidence of strong deformation in this orogen, and it has had a long and complex geological history. We investigated the structure of the Moho in the southern Qinling orogen using large dynamite shot imaging techniques. By integrating the analysis of the single-shot and the move-out corrections profile, we determined the structure of the Moho beneath the northern Dabashan thrust belt and the southern Qinling orogen, including the mantle suture beneath Fenghuang mountain. The Moho is divided into two parts by the mantle suture zone beneath Fenghuang mountain： （1） from Ziyang to Hanyin, the north-dipping Moho is at about 45-55 km depth and the depth increases rapidly; and （2） from Hanyin to Ningshan, the south-dipping Moho is at about 40-45 km depth and shallows slowly. The mantle suture is located beneath Fenghuang mountain, and the Moho overlaps at this location： the shallower Moho is connected to the northern part of China, and the deeper Moho is connected to the southern part. This may indicate that the lithosphere in the Sichuan basin subducts to the Qinling block and that the subduction frontier reaches at least as far as Fenghuang mountain.
基金supported by the National Key Basic Research Program of China(Grant No.2013CB429701)the National Natural Science Foundation of China(Grant Nos.41606083,91958210,41606050 and 41210005)+1 种基金AoShan Technological Innovation Projects of National Laboratory for Marine Science and Technology(Qingdao)(2015ASKJ03)National Marine Geological Special Project(DD20190236,DD20190365,DD20190377)。
文摘The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.
文摘Seismic wave reflection method is an advanced geophysical detection method in tunnel geological prediction.It is more sensitive and effective in detecting geological anomalies such as fault fracture zone and karst.In order to verify the prediction efficacy and accuracy of the seismic wave reflection method with different instruments and equipment(tunnel geological prediction[TGP]/tunnel seismic prediction[TSP])and different vibration modes(hammering,explosives),a comparison test was carried out in Jinping Tunnel.The test results showed that the time-consumption of the hammering source was short,which can greatly reduce the impact on the construction site;different vibration sources methods of seismic wave reflection can predict the unfavorable geological sections accurately.
