Follow-up of environmental impacts is an integral part of the Environmental Impact Assessment (EIA) process, closely related to the effectiveness of the instrument. EIA follow-up has been receiving a lot of interest f...Follow-up of environmental impacts is an integral part of the Environmental Impact Assessment (EIA) process, closely related to the effectiveness of the instrument. EIA follow-up has been receiving a lot of interest from scientists and practitioners, though it is recognized as one of the weakest points of EIA systems globally. Also, EIA follow-up is influenced by the context, mainly in terms of the types of projects or activities and their related impacts on the environment. Therefore, the present paper is focused on the investigation of the follow-up stage applied to the activity of seismic survey coupled with offshore oil & gas exploitation in Brazil. Research was based on a qualitative approach that included document analysis and semi-structured interviews with analysts involved in EIA processes, and sought to generate evidence of effectiveness of the EIA follow-up as conducted by the Federal Environment Agency (Ibama) in order to situate the practice of follow-up in the broader context of international best practice principles. Based on the findings, it was concluded that, due to the peculiarities of offshore seismic survey, it is necessary to promote adaptations in the procedures for monitoring impacts in order to ensure proper alignment with the principles and conceptual foundations that guide EIA practice. Specifically, the timing of the execution of the activity imposes challenges for its integration into the “conventional” cycle that has guided the monitoring of the impacts in the EIA of projects.展开更多
This paper presents the survey and research work of two land-sea profiles in the Bohai Sea, China, carried out in 2010-2011, including the seismic sources on land and in the sea, the ocean bottom seismographs (OBS) ...This paper presents the survey and research work of two land-sea profiles in the Bohai Sea, China, carried out in 2010-2011, including the seismic sources on land and in the sea, the ocean bottom seismographs (OBS) and their recovery, the coupling of OBS and the environment noise in sea area, the data quality of OBSs, and the result of data analysis. We focused on the investigation of crustal structures revealed by the two NE/EW-trending joint land-sea profiles. In combination with the Pn-velocity distribution and gravity- magnetic inversion results in the North China Craton, we propose that the undulation of the Moho interface in the Bohai and surrounding areas is not strong, and the lithospheric thinning is mainly caused by the thinning of its mantle part. The research result indicates that obvious lateral variations of Moho depth and seismic velocity appear nearby all the large-scale faults in Bohai Sea, and there is evidence of underplating and reforming of the lower crust by mantle material in the Bohai area. However, geophysical evidence does not appear to support the "mantle plume" or "delamination" model for the North China Craton destruction. The crustal structure of the Bohai Sea revealed "a relatively normal crust and obviously thinned mantle lid", local velocity anomalies and instability phenomena in the crust. These features may represent a combined effect of North China-Yangtze collision at an early stage and the remote action of Pacific plate subduction at a late stage.展开更多
In order to effectively detect potential geology anomalous bodies in coal bearing formation,such as coal seam thickness variation,small faults,goafs and collapse columns,and provide scientific guidance for safe and ef...In order to effectively detect potential geology anomalous bodies in coal bearing formation,such as coal seam thickness variation,small faults,goafs and collapse columns,and provide scientific guidance for safe and efficient mining,the SUMMIT-II EX explosion-proof seismic slot wave instrument,produced by German DMT Company,was used to detect the underground channel wave with the help of transmission method,reflection method and transflective method.Region area detection experiment in mining face had been carried out thanks to the advantage of channel wave,such as its great dispersion,abundant geology information,strong anti-interference ability and long-distance detecting.The experimental results showed that:(1)Coal seam thickness variation in extremely unstable coal seam has been quantitatively interpreted with an accuracy of more than 80%generally;(2)The faults,goafs and collapse columns could be detected and predicted accurately;(3)Experimental detection of gas enrichment areas,stress concentration regions and water inrush risk zone has been collated;(4)A research system of disaster-causing geology anomalous body detection by in-seam seismic survey has been built,valuable and innovative achievements have been got.Series of innovation obtained for the first time in this study indicated that it was more effective to detect disaster-causing potential geology anomalies by in-seam seismic survey than by ground seismic survey.It had significant scientific value and application prospect under complex coal seam conditions.展开更多
As a high-precision survey method,seismic surveying has been increasingly applied to inland water research,although its application to artificial reservoirs has remained limited.As a special artificial water body,rese...As a high-precision survey method,seismic surveying has been increasingly applied to inland water research,although its application to artificial reservoirs has remained limited.As a special artificial water body,reservoirs have important effects on the fluvial transport of material from land to ocean,and inevitably have complex terrain which can complicate and distort the results of seismic surveys.Therefore,there are still some problems need to be resolved in the application of seismic surveys in reservoirs with complex terrain.For this study,the Dongfeng Reservoir located in the upper reaches of the Wujiang River was chosen as an example to test the seismic survey method.Our testing showed that(1)because of the complex underwater terrain,the signal-to-noise ratio of the echo signal in canyon reservoir is low,making it difficult to determine sediment layers thicknesses in some areas;and(2)due to the large spatial heterogeneity of sediment distribution,insufficient density of cross-sections can lead to inaccurate interpolation results.To improve the accuracy of calculations,a mathematical method was used.Ultimately,the total burial mass of sediment was estimated at 2.85 x 107 tons,and the average burial rates of total organic carbon,total phosphorus,and total nitrogen were estimated at 0.194,0.011,and 0.014 g cm-2 year-1,respectively.These values were close to the results of previous studies and hydrographic station data,indicating that seismic survey can be a reliable and efficient method for the mapping of reservoirs.展开更多
Site engineering seismic survey provides basic data for seismic effect analysis. As an important parameter of soil, shear-wave velocity is usually obtained through wave velocity testing in borehole. In this paper, the...Site engineering seismic survey provides basic data for seismic effect analysis. As an important parameter of soil, shear-wave velocity is usually obtained through wave velocity testing in borehole. In this paper, the passive source surface-wave method is introduced into the site engineering seismic survey and practically applied in an engineering site of Shijingshan District. By recording the ubiquitous weak vibration on the earth surface, extract the dispersion curve from the surface-wave components using the SPAC method and obtain the shear-wave velocity structure from inversion. Over the depth of 42 m under- ground, it totally consists of five layers with interface depth of 3.31, 4.50, 7.23, 17.41, and 42.00 m; and shear-wave velocity of 144.0, 198.3, 339.4, 744.2, and 903.7 m/s, respectively. The inversion result is used to evaluate site classification, determine the maximum shear modulus of soil, provide basis for further seismic hazard analysis and site assessment or site zoning, etc. The result shows that the passive source surface-wave method is feasible in the site engineering seismic survey and can replace boreholes,shorten survey period, and reduce engineering cost to some extent.展开更多
The accurate prediction of formation pressure is important in oil/gas exploration and development.However,the achievement of this goal remains challenging,due to insufficient logging data and the low predictive data a...The accurate prediction of formation pressure is important in oil/gas exploration and development.However,the achievement of this goal remains challenging,due to insufficient logging data and the low predictive data accuracy from seismic data.In this work,a case study was carried out in the Baima area of Wulong,in order to develop a workflow for accurately predicting shale gas formation pressure.The multi-channel stack method was first used,as well as the inversion of single-channel seismic data,to construct velocity and density models of the formation.Combined with the existing welllogging data,the velocity and density models of the whole well section were established.The shale gas formation pressure was then estimated using the Eaton method.The results show that the multi-channel seismic stacking method has a higher accuracy than the inversion of the formation velocity obtained by the single-channel seismic method.The discrepancies between our predicted formation pressure and the actual formation pressure measurement are within an acceptable range,indicating that our workflow is effective.展开更多
In the presence of background noise,arrival times picked from a surface microseismic data set usually include a number of false picks that can lead to uncertainty in location estimation.To eliminate false picks and im...In the presence of background noise,arrival times picked from a surface microseismic data set usually include a number of false picks that can lead to uncertainty in location estimation.To eliminate false picks and improve the accuracy of location estimates,we develop an association algorithm termed RANSAC-based Arrival Time Event Clustering(RATEC)that clusters picked arrival times into event groups based on random sampling and fitting moveout curves that approximate hyperbolas.Arrival times far from the fitted hyperbolas are classified as false picks and removed from the data set prior to location estimation.Simulations of synthetic data for a 1-D linear array show that RATEC is robust under different noise conditions and generally applicable to various types of subsurface structures.By generalizing the underlying moveout model,RATEC is extended to the case of a 2-D surface monitoring array.The effectiveness of event location for the 2-D case is demonstrated using a data set collected by the 5200-element dense Long Beach array.The obtained results suggest that RATEC is effective in removing false picks and hence can be used for phase association before location estimates.展开更多
At present,there is less theoretical research and practical experience in the aspect of ultrashallow seismic exploration to the target layers at depths of only tens of meters both at home and abroad. Seismic explorati...At present,there is less theoretical research and practical experience in the aspect of ultrashallow seismic exploration to the target layers at depths of only tens of meters both at home and abroad. Seismic exploration plays an important role in the location of faults and active structures,but the depth dozens of meters below the ground surface is the blind area of any kind of deep and shallow seismic exploration. Starting from the point of view of detecting urban active faults,and using related theories and methods of geology,geophysics and mathematics,the paper discusses the preconditions for acquiring efficient ultra-shallow seismic survey results in complicated geological backgrounds in Qingdao.Taking the Qingdao area as an example in this paper,we study the depth condition of Quaternary deposits,and apply 4-8 stacking folds to satisfy the requirement to get the exploration results with high-resolution and high-SNR. Preliminary results reveal that selecting a proper surveillance layout is one of the keys to acquire authentic exploration results in ultra-shallow P-wave reflection exploration. Our results also show that ultrashallow seismic reflection method in detecting faults in the Qingdao area has good application prospects.展开更多
The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks i...The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.展开更多
Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used ...Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used for automatic accurate onset phase picking based on the proporty of dense seismic array observations. In our method, the Akaike's information criterion (AIC) for the single channel observation and the least-squares cross-correlation for the multi-channel observation are combined together. The tests by the seismic array observation data after triggering with the short-term average/long-term average (STA/LTA) technique show that the phase picking error is less than 0.3 s for local events by using the single channel AIC algorithm. In terms of multi-channel least-squares cross-correlation technique, the clear teleseismic P onset can be detected reliably. Even for the teleseismic records with high noise level, our algorithm is also able to effectually avoid manual misdetections.展开更多
The October 23, 2011 M7.2 Tabanli - Van and November 9, 2011 M5.2 Edremit - Van earthquakes caused damage in a widespread area across the Van province in Turkey. The ground motions, the damage caused by these earthqua...The October 23, 2011 M7.2 Tabanli - Van and November 9, 2011 M5.2 Edremit - Van earthquakes caused damage in a widespread area across the Van province in Turkey. The ground motions, the damage caused by these earthquakes and the recent progress related to recovery efforts are presented herein. First, the key properties of the recorded strong ground motions like spectral amplitudes and directionality are evaluated. The observed damage in the affected reinforced concrete and masonry structures are discussed. The set of common structural damage mechanisms (i.e., soft story failure, torsional response due to plan irregularity, short column failure, pull out failure, pounding) observed in the damaged buildings were identified. The relationship between the key structural properties and the extent of damage is investigated. The primary loss drivers across the region were identified to be the poor quality of workmanship and improper use of building materials. The results from the investigation suggest that a large portion of the loss could have been prevented if sufficient attention and care were given to the implementation of the design regulations and in particular to the construction practice. Lastly, the recent progress in the ongoing rebuildin~ activities is presented.展开更多
By using the waveform data recorded during the site survey of Lanzhou Seismic Array, the author calculated and analyzed the correlation of the signal and noise between the site pairs and found that the ideal radii of ...By using the waveform data recorded during the site survey of Lanzhou Seismic Array, the author calculated and analyzed the correlation of the signal and noise between the site pairs and found that the ideal radii of the two concentric rings for Lanzhou Seismic Array were 380 m and 1500 m, respectively. According to the radius limit and other requirements, nine sites were chosen to make a seismic array, and then the detection and location ability of the array were estimated.展开更多
Understanding rock strength is essential when undertaking major excavation projects,as accurate assessments ensure both safe and cost-effective engineered slopes.Balancing the cost-safety trade-off becomes more impera...Understanding rock strength is essential when undertaking major excavation projects,as accurate assessments ensure both safe and cost-effective engineered slopes.Balancing the cost-safety trade-off becomes more imperative during the construction of critical infrastructure such as nuclear power stations,where key components are built within relatively deep excavations.Designing these engineered slopes is reliant on rock strength models,which are generally parameterised using estimates of rock properties(e.g.unconfined compressive strength,rock disturbance)measured prior to the commencement of works.However,the physical process of excavation weakens the remaining rock mass.Therefore,the model also requires an adjustment for the anticipated rock disturbance.In practice,this parameter is difficult to quantify and as a result it is often poorly constrained.This can have a significant impact on the final design and cost of excavation.We present results from passive and active seismic surveys,which image the extent and degree of disturbance within recently excavated slopes at the construction site of Hinkley Point C nuclear power station.Results from active seismic surveys indicate that the disturbance is primarily confined to 0.5 m from the excavated face.In conjunction,passive monitoring is used to detected seismic events corresponding to fracturing on the cm-scale and event locations are in agreement with 0.5 m of disturbance into the rock face.This suggests rock disturbance at this site is relatively low and occurred during and immediately after the excavation.A ratio of seismic velocities recorded before and after excavations are used to determine the disturbance parameter required for the Hoek eBrown rock failure criterion,and we assess that rock disturbance is low with the magnitude of the disturbance diminishing more quickly than expected into the excavated slope.Seismic methods provide a low-cost and quick method to assess excavation related rock mass disturbance,which can lead to cost reductions in large excavation projects.展开更多
The zones of thawed ground in the permafrost area are most dangerous from engineer-geologist effect point of view. Detection of such zones, as making forecast of their movement is the main task of engineer-geologist s...The zones of thawed ground in the permafrost area are most dangerous from engineer-geologist effect point of view. Detection of such zones, as making forecast of their movement is the main task of engineer-geologist survey been held in railway industry. This paper presents general issues concerning railway construction and operation in permafrost areas. Comprehensive geophysical methods to monitor the development of thawed soils axe considered in detail. The main physical parameters which help define permafrost and thawed soil patches are described. Author of current paper pointed out main factors, allowing predicting potential areas of development of thawed grounds. They offered set non-destructive methods: GPR investigations, seismic survey and elec- tric exploration. Whole sets of geophysical data: electric resistivity, velocity of S-wave and P-wave (and their correlation), allow us with high confidence specify characteristics and state of soil either under the line of road, or near it. At the same time the meth- od allows to predict direction of further development of thawed ground area.展开更多
1 SURVEY OF GLOBAL SEISMICITY A total of 5 strong earthquakes with M S≥7.0 occurred in the first half of 2018(from January 1 to May 31,2018)throughout the world,according to CENC(China Earthquake Networks Center),in...1 SURVEY OF GLOBAL SEISMICITY A total of 5 strong earthquakes with M S≥7.0 occurred in the first half of 2018(from January 1 to May 31,2018)throughout the world,according to CENC(China Earthquake Networks Center),including one with M S≥8.0(M W7.9),which occurred on January 23,2018 in Alaska(Fig.1).The 2018 M S8.0 Alaska earthquake was located in the north of the Circum-Pacific Seismic Belt.The mainshock was slip type and the rupture was unilateral along the NW direction,with maximum intensityⅩ.Features of global seismicity of M S≥7.0 in the first half year of 2018 are as follows.1.1 The Global Seismicity Was Similar to 2017 But Weaker Than Previous Years One earthquake with M S≥8.0 occurred in the first half of 2018.The global seismic strength stayed nearly the same compared with the earthquake with M S≥8.0 in 2017(Fig.2(a)).There were 5 earthquakes with M≥7.0 occurring in the world in the first half of 2018.The seismic frequency was similar to 2017,which had 8 strong earthquakes with M S≥7.0,but was significantly lower than the annual average of 19 strong earthquakes(Fig.2(b)).展开更多
A field damage survey of 1,005 buildings damaged by the Wenchuan Earthquake in Dujiangyan City was carried out and the resulting data was analyzed using the statistical method. It is shown that buildings that were sei...A field damage survey of 1,005 buildings damaged by the Wenchuan Earthquake in Dujiangyan City was carried out and the resulting data was analyzed using the statistical method. It is shown that buildings that were seismically designed achieved the desired seismic fortification target; they sustained less damage than the non-seismically designed buildings. Among the seismically designed buildings investigated, RC frame buildings performed the best in terms of seismic resistance. Masonry buildings with a ground story of RC frame structure were the second best, and masonry buildings performed the worst. Considering building height, multistory buildings sustained more severe damage than high-rise buildings and 2- and 3-story buildings. Compared to residential buildings, public buildings, such as schools and hospitals, suffered more severe damage.展开更多
The Ludian County of Yunnan Province in southwestern China was struck by an Ms6.5 earthquake on August 3, 2014, which was another destructive event following the Ms8.0 Wenchuan earthquake in 2008, Ms7.1 Yushu earthqua...The Ludian County of Yunnan Province in southwestern China was struck by an Ms6.5 earthquake on August 3, 2014, which was another destructive event following the Ms8.0 Wenchuan earthquake in 2008, Ms7.1 Yushu earthquake in 2010, and Ms7.0 Lushan earthquake in 2013. National Strong-Motion Observation Network System of China collected 74 strong motion recordings, which the maximum peak ground acceleration recorded by the 053LLT station in Longtoushan Town was 949 cm/s2 in E-W component. The observed PGAs and spectral ordinates were compared with ground-motion prediction equation in China and the NGA-West2 developed by Pacific Earthquake Engineering Researcher Center. This earthquake is considered as the first case for testing applicability of NGA-West2 in China. Results indicate that the observed PGAs and the 5 % damped pseudo-response spectral accelerations are significantly lower than the pre- dicted ones. The field survey around some typical strong motion stations verified that the earthquake damage was consistent with the official isoseismal by China Earthquake Administration.展开更多
A comprehensive study is presented for empirical seismic vulnerability assessment of typical structural types, representative of the building stock of Southern Europe, based on a large set of damage statistics. The ob...A comprehensive study is presented for empirical seismic vulnerability assessment of typical structural types, representative of the building stock of Southern Europe, based on a large set of damage statistics. The observational database was obtained from post-earthquake surveys carried out in the area struck by the September 7, 1999 Athens earthquake. After analysis of the collected observational data, a unified damage database has been created which comprises 180,945 damaged buildings from/after the near-field area of the earthquake. The damaged buildings are classified in specific structural types, according to the materials, seismic codes and construction techniques in Southern Europe. The seismic demand is described in terms of both the regional macroseismic intensity and the ratio αg/ao, where αg is the maximum peak ground acceleration (PGA) of the earthquake event and ao is the unique value PGA that characterizes each municipality shown on the Greek hazard map. The relative and cumulative frequencies of the different damage states for each structural type and each intensity level are computed in terms of damage ratio. Damage probability matrices (DPMs) and vulnerability curves are obtained for specific structural types. A comparison analysis is fulfilled between the produced and the existing vulnerability models.展开更多
The South China Sea(SCS)is the hotspot of geological scientific research and nature resource exploration and development due to the potential for enormous hydrocarbon resource development and a complex formation and e...The South China Sea(SCS)is the hotspot of geological scientific research and nature resource exploration and development due to the potential for enormous hydrocarbon resource development and a complex formation and evolution process.The SCS has experienced complex geological processes including continental lithospheric breakup,seafloor spreading and oceanic crust subduction,which leads debates for decades.However,there are still no clear answers regarding to the following aspects:the crustal and Moho structure,the structure of the continent-ocean transition zone,the formation and evolution process and geodynamic mechanism,and deep processes and their coupling relationships with the petroliferous basins in the SCS.Under the guidance of the“Deep-Earth”science and technology innovation strategy of the Ministry of Natural Resources,deep structural and comprehensive geological research are carried out in the SCS.Geophysical investigations such as long array-large volume deep reflection seismic,gravity,magnetism and ocean bottom seismometer are carried out.The authors proposed that joint gravitymagnetic-seismic inversion should be used to obtain deep crustal information in the SCS and construct high resolution deep structural sections in different regions of the SCS.This paper systematically interpreted the formation and evolution of the SCS and explored the coupling relationship between deep structure and evolution of Mesozoic-Cenozoic basins in the SCS.It is of great significance for promoting the geosystem scientific research and resource exploration of the SCS.展开更多
文摘Follow-up of environmental impacts is an integral part of the Environmental Impact Assessment (EIA) process, closely related to the effectiveness of the instrument. EIA follow-up has been receiving a lot of interest from scientists and practitioners, though it is recognized as one of the weakest points of EIA systems globally. Also, EIA follow-up is influenced by the context, mainly in terms of the types of projects or activities and their related impacts on the environment. Therefore, the present paper is focused on the investigation of the follow-up stage applied to the activity of seismic survey coupled with offshore oil & gas exploitation in Brazil. Research was based on a qualitative approach that included document analysis and semi-structured interviews with analysts involved in EIA processes, and sought to generate evidence of effectiveness of the EIA follow-up as conducted by the Federal Environment Agency (Ibama) in order to situate the practice of follow-up in the broader context of international best practice principles. Based on the findings, it was concluded that, due to the peculiarities of offshore seismic survey, it is necessary to promote adaptations in the procedures for monitoring impacts in order to ensure proper alignment with the principles and conceptual foundations that guide EIA practice. Specifically, the timing of the execution of the activity imposes challenges for its integration into the “conventional” cycle that has guided the monitoring of the impacts in the EIA of projects.
基金The National Natural Science Foundation of China under contract Nos 41210005,41074058 and 90814011the National High Technique R&D Program (863 Program) under contract Nos 2009AA093401 and 2011ZX05008-006-30
文摘This paper presents the survey and research work of two land-sea profiles in the Bohai Sea, China, carried out in 2010-2011, including the seismic sources on land and in the sea, the ocean bottom seismographs (OBS) and their recovery, the coupling of OBS and the environment noise in sea area, the data quality of OBSs, and the result of data analysis. We focused on the investigation of crustal structures revealed by the two NE/EW-trending joint land-sea profiles. In combination with the Pn-velocity distribution and gravity- magnetic inversion results in the North China Craton, we propose that the undulation of the Moho interface in the Bohai and surrounding areas is not strong, and the lithospheric thinning is mainly caused by the thinning of its mantle part. The research result indicates that obvious lateral variations of Moho depth and seismic velocity appear nearby all the large-scale faults in Bohai Sea, and there is evidence of underplating and reforming of the lower crust by mantle material in the Bohai area. However, geophysical evidence does not appear to support the "mantle plume" or "delamination" model for the North China Craton destruction. The crustal structure of the Bohai Sea revealed "a relatively normal crust and obviously thinned mantle lid", local velocity anomalies and instability phenomena in the crust. These features may represent a combined effect of North China-Yangtze collision at an early stage and the remote action of Pacific plate subduction at a late stage.
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.41130419).
文摘In order to effectively detect potential geology anomalous bodies in coal bearing formation,such as coal seam thickness variation,small faults,goafs and collapse columns,and provide scientific guidance for safe and efficient mining,the SUMMIT-II EX explosion-proof seismic slot wave instrument,produced by German DMT Company,was used to detect the underground channel wave with the help of transmission method,reflection method and transflective method.Region area detection experiment in mining face had been carried out thanks to the advantage of channel wave,such as its great dispersion,abundant geology information,strong anti-interference ability and long-distance detecting.The experimental results showed that:(1)Coal seam thickness variation in extremely unstable coal seam has been quantitatively interpreted with an accuracy of more than 80%generally;(2)The faults,goafs and collapse columns could be detected and predicted accurately;(3)Experimental detection of gas enrichment areas,stress concentration regions and water inrush risk zone has been collated;(4)A research system of disaster-causing geology anomalous body detection by in-seam seismic survey has been built,valuable and innovative achievements have been got.Series of innovation obtained for the first time in this study indicated that it was more effective to detect disaster-causing potential geology anomalies by in-seam seismic survey than by ground seismic survey.It had significant scientific value and application prospect under complex coal seam conditions.
基金funded by the National Natural Science Foundation of China (No. 41573064)the National Key Research and Development program of China (No. 2016YFA0601003)
文摘As a high-precision survey method,seismic surveying has been increasingly applied to inland water research,although its application to artificial reservoirs has remained limited.As a special artificial water body,reservoirs have important effects on the fluvial transport of material from land to ocean,and inevitably have complex terrain which can complicate and distort the results of seismic surveys.Therefore,there are still some problems need to be resolved in the application of seismic surveys in reservoirs with complex terrain.For this study,the Dongfeng Reservoir located in the upper reaches of the Wujiang River was chosen as an example to test the seismic survey method.Our testing showed that(1)because of the complex underwater terrain,the signal-to-noise ratio of the echo signal in canyon reservoir is low,making it difficult to determine sediment layers thicknesses in some areas;and(2)due to the large spatial heterogeneity of sediment distribution,insufficient density of cross-sections can lead to inaccurate interpolation results.To improve the accuracy of calculations,a mathematical method was used.Ultimately,the total burial mass of sediment was estimated at 2.85 x 107 tons,and the average burial rates of total organic carbon,total phosphorus,and total nitrogen were estimated at 0.194,0.011,and 0.014 g cm-2 year-1,respectively.These values were close to the results of previous studies and hydrographic station data,indicating that seismic survey can be a reliable and efficient method for the mapping of reservoirs.
基金supported by National Natural Science Foundation of China (No. 41174085)Chinese Academy of Sciences (KZZD-EW-TZ-19)China Geological Survey (12120113101400)
文摘Site engineering seismic survey provides basic data for seismic effect analysis. As an important parameter of soil, shear-wave velocity is usually obtained through wave velocity testing in borehole. In this paper, the passive source surface-wave method is introduced into the site engineering seismic survey and practically applied in an engineering site of Shijingshan District. By recording the ubiquitous weak vibration on the earth surface, extract the dispersion curve from the surface-wave components using the SPAC method and obtain the shear-wave velocity structure from inversion. Over the depth of 42 m under- ground, it totally consists of five layers with interface depth of 3.31, 4.50, 7.23, 17.41, and 42.00 m; and shear-wave velocity of 144.0, 198.3, 339.4, 744.2, and 903.7 m/s, respectively. The inversion result is used to evaluate site classification, determine the maximum shear modulus of soil, provide basis for further seismic hazard analysis and site assessment or site zoning, etc. The result shows that the passive source surface-wave method is feasible in the site engineering seismic survey and can replace boreholes,shorten survey period, and reduce engineering cost to some extent.
基金support of the National Natural Science Key Foundation of China(Grant Nos.91958206,91858215)the Key Research and Development Program of Shandong(Grant No.2019GHY112019)+2 种基金the China Sponsorship Council(Grant No.201806335026)the Opening Foundation of Key Lab of Submarine Geosciences and Prospecting Techniques,MOE,Ocean University of China(Grant No.SGPT-20210F-06)the Fundamental Research Funds for the Central Universities(Grant No.202161013)。
文摘The accurate prediction of formation pressure is important in oil/gas exploration and development.However,the achievement of this goal remains challenging,due to insufficient logging data and the low predictive data accuracy from seismic data.In this work,a case study was carried out in the Baima area of Wulong,in order to develop a workflow for accurately predicting shale gas formation pressure.The multi-channel stack method was first used,as well as the inversion of single-channel seismic data,to construct velocity and density models of the formation.Combined with the existing welllogging data,the velocity and density models of the whole well section were established.The shale gas formation pressure was then estimated using the Eaton method.The results show that the multi-channel seismic stacking method has a higher accuracy than the inversion of the formation velocity obtained by the single-channel seismic method.The discrepancies between our predicted formation pressure and the actual formation pressure measurement are within an acceptable range,indicating that our workflow is effective.
文摘In the presence of background noise,arrival times picked from a surface microseismic data set usually include a number of false picks that can lead to uncertainty in location estimation.To eliminate false picks and improve the accuracy of location estimates,we develop an association algorithm termed RANSAC-based Arrival Time Event Clustering(RATEC)that clusters picked arrival times into event groups based on random sampling and fitting moveout curves that approximate hyperbolas.Arrival times far from the fitted hyperbolas are classified as false picks and removed from the data set prior to location estimation.Simulations of synthetic data for a 1-D linear array show that RATEC is robust under different noise conditions and generally applicable to various types of subsurface structures.By generalizing the underlying moveout model,RATEC is extended to the case of a 2-D surface monitoring array.The effectiveness of event location for the 2-D case is demonstrated using a data set collected by the 5200-element dense Long Beach array.The obtained results suggest that RATEC is effective in removing false picks and hence can be used for phase association before location estimates.
基金sponsored by the PhD Research Foundation of Hebei GEO University(BQ2017027)
文摘At present,there is less theoretical research and practical experience in the aspect of ultrashallow seismic exploration to the target layers at depths of only tens of meters both at home and abroad. Seismic exploration plays an important role in the location of faults and active structures,but the depth dozens of meters below the ground surface is the blind area of any kind of deep and shallow seismic exploration. Starting from the point of view of detecting urban active faults,and using related theories and methods of geology,geophysics and mathematics,the paper discusses the preconditions for acquiring efficient ultra-shallow seismic survey results in complicated geological backgrounds in Qingdao.Taking the Qingdao area as an example in this paper,we study the depth condition of Quaternary deposits,and apply 4-8 stacking folds to satisfy the requirement to get the exploration results with high-resolution and high-SNR. Preliminary results reveal that selecting a proper surveillance layout is one of the keys to acquire authentic exploration results in ultra-shallow P-wave reflection exploration. Our results also show that ultrashallow seismic reflection method in detecting faults in the Qingdao area has good application prospects.
基金jointly supported by the project of Chinese National Natural Science Foundation(42107485)National Key R&D Program(2020YFC1512400,2018YFC800804)China Geological Survey(DD20190282,DD20221734,and DD20230323)。
文摘The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.
基金National Natural Science Foundation of China (Grant No. 40234043).
文摘Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used for automatic accurate onset phase picking based on the proporty of dense seismic array observations. In our method, the Akaike's information criterion (AIC) for the single channel observation and the least-squares cross-correlation for the multi-channel observation are combined together. The tests by the seismic array observation data after triggering with the short-term average/long-term average (STA/LTA) technique show that the phase picking error is less than 0.3 s for local events by using the single channel AIC algorithm. In terms of multi-channel least-squares cross-correlation technique, the clear teleseismic P onset can be detected reliably. Even for the teleseismic records with high noise level, our algorithm is also able to effectually avoid manual misdetections.
文摘The October 23, 2011 M7.2 Tabanli - Van and November 9, 2011 M5.2 Edremit - Van earthquakes caused damage in a widespread area across the Van province in Turkey. The ground motions, the damage caused by these earthquakes and the recent progress related to recovery efforts are presented herein. First, the key properties of the recorded strong ground motions like spectral amplitudes and directionality are evaluated. The observed damage in the affected reinforced concrete and masonry structures are discussed. The set of common structural damage mechanisms (i.e., soft story failure, torsional response due to plan irregularity, short column failure, pull out failure, pounding) observed in the damaged buildings were identified. The relationship between the key structural properties and the extent of damage is investigated. The primary loss drivers across the region were identified to be the poor quality of workmanship and improper use of building materials. The results from the investigation suggest that a large portion of the loss could have been prevented if sufficient attention and care were given to the implementation of the design regulations and in particular to the construction practice. Lastly, the recent progress in the ongoing rebuildin~ activities is presented.
文摘By using the waveform data recorded during the site survey of Lanzhou Seismic Array, the author calculated and analyzed the correlation of the signal and noise between the site pairs and found that the ideal radii of the two concentric rings for Lanzhou Seismic Array were 380 m and 1500 m, respectively. According to the radius limit and other requirements, nine sites were chosen to make a seismic array, and then the detection and location ability of the array were estimated.
文摘Understanding rock strength is essential when undertaking major excavation projects,as accurate assessments ensure both safe and cost-effective engineered slopes.Balancing the cost-safety trade-off becomes more imperative during the construction of critical infrastructure such as nuclear power stations,where key components are built within relatively deep excavations.Designing these engineered slopes is reliant on rock strength models,which are generally parameterised using estimates of rock properties(e.g.unconfined compressive strength,rock disturbance)measured prior to the commencement of works.However,the physical process of excavation weakens the remaining rock mass.Therefore,the model also requires an adjustment for the anticipated rock disturbance.In practice,this parameter is difficult to quantify and as a result it is often poorly constrained.This can have a significant impact on the final design and cost of excavation.We present results from passive and active seismic surveys,which image the extent and degree of disturbance within recently excavated slopes at the construction site of Hinkley Point C nuclear power station.Results from active seismic surveys indicate that the disturbance is primarily confined to 0.5 m from the excavated face.In conjunction,passive monitoring is used to detected seismic events corresponding to fracturing on the cm-scale and event locations are in agreement with 0.5 m of disturbance into the rock face.This suggests rock disturbance at this site is relatively low and occurred during and immediately after the excavation.A ratio of seismic velocities recorded before and after excavations are used to determine the disturbance parameter required for the Hoek eBrown rock failure criterion,and we assess that rock disturbance is low with the magnitude of the disturbance diminishing more quickly than expected into the excavated slope.Seismic methods provide a low-cost and quick method to assess excavation related rock mass disturbance,which can lead to cost reductions in large excavation projects.
基金Russian Railways,and Nauka-MSURT for financial support
文摘The zones of thawed ground in the permafrost area are most dangerous from engineer-geologist effect point of view. Detection of such zones, as making forecast of their movement is the main task of engineer-geologist survey been held in railway industry. This paper presents general issues concerning railway construction and operation in permafrost areas. Comprehensive geophysical methods to monitor the development of thawed soils axe considered in detail. The main physical parameters which help define permafrost and thawed soil patches are described. Author of current paper pointed out main factors, allowing predicting potential areas of development of thawed grounds. They offered set non-destructive methods: GPR investigations, seismic survey and elec- tric exploration. Whole sets of geophysical data: electric resistivity, velocity of S-wave and P-wave (and their correlation), allow us with high confidence specify characteristics and state of soil either under the line of road, or near it. At the same time the meth- od allows to predict direction of further development of thawed ground area.
文摘1 SURVEY OF GLOBAL SEISMICITY A total of 5 strong earthquakes with M S≥7.0 occurred in the first half of 2018(from January 1 to May 31,2018)throughout the world,according to CENC(China Earthquake Networks Center),including one with M S≥8.0(M W7.9),which occurred on January 23,2018 in Alaska(Fig.1).The 2018 M S8.0 Alaska earthquake was located in the north of the Circum-Pacific Seismic Belt.The mainshock was slip type and the rupture was unilateral along the NW direction,with maximum intensityⅩ.Features of global seismicity of M S≥7.0 in the first half year of 2018 are as follows.1.1 The Global Seismicity Was Similar to 2017 But Weaker Than Previous Years One earthquake with M S≥8.0 occurred in the first half of 2018.The global seismic strength stayed nearly the same compared with the earthquake with M S≥8.0 in 2017(Fig.2(a)).There were 5 earthquakes with M≥7.0 occurring in the world in the first half of 2018.The seismic frequency was similar to 2017,which had 8 strong earthquakes with M S≥7.0,but was significantly lower than the annual average of 19 strong earthquakes(Fig.2(b)).
文摘A field damage survey of 1,005 buildings damaged by the Wenchuan Earthquake in Dujiangyan City was carried out and the resulting data was analyzed using the statistical method. It is shown that buildings that were seismically designed achieved the desired seismic fortification target; they sustained less damage than the non-seismically designed buildings. Among the seismically designed buildings investigated, RC frame buildings performed the best in terms of seismic resistance. Masonry buildings with a ground story of RC frame structure were the second best, and masonry buildings performed the worst. Considering building height, multistory buildings sustained more severe damage than high-rise buildings and 2- and 3-story buildings. Compared to residential buildings, public buildings, such as schools and hospitals, suffered more severe damage.
基金supported by the Science Foundation of Institute of Engineering Mechanics, China Earthquake Administration (CEA) under Grant No. 2014B06the National Natural Science Foundation of China Nos. 51308515 and 51278473
文摘The Ludian County of Yunnan Province in southwestern China was struck by an Ms6.5 earthquake on August 3, 2014, which was another destructive event following the Ms8.0 Wenchuan earthquake in 2008, Ms7.1 Yushu earthquake in 2010, and Ms7.0 Lushan earthquake in 2013. National Strong-Motion Observation Network System of China collected 74 strong motion recordings, which the maximum peak ground acceleration recorded by the 053LLT station in Longtoushan Town was 949 cm/s2 in E-W component. The observed PGAs and spectral ordinates were compared with ground-motion prediction equation in China and the NGA-West2 developed by Pacific Earthquake Engineering Researcher Center. This earthquake is considered as the first case for testing applicability of NGA-West2 in China. Results indicate that the observed PGAs and the 5 % damped pseudo-response spectral accelerations are significantly lower than the pre- dicted ones. The field survey around some typical strong motion stations verified that the earthquake damage was consistent with the official isoseismal by China Earthquake Administration.
文摘A comprehensive study is presented for empirical seismic vulnerability assessment of typical structural types, representative of the building stock of Southern Europe, based on a large set of damage statistics. The observational database was obtained from post-earthquake surveys carried out in the area struck by the September 7, 1999 Athens earthquake. After analysis of the collected observational data, a unified damage database has been created which comprises 180,945 damaged buildings from/after the near-field area of the earthquake. The damaged buildings are classified in specific structural types, according to the materials, seismic codes and construction techniques in Southern Europe. The seismic demand is described in terms of both the regional macroseismic intensity and the ratio αg/ao, where αg is the maximum peak ground acceleration (PGA) of the earthquake event and ao is the unique value PGA that characterizes each municipality shown on the Greek hazard map. The relative and cumulative frequencies of the different damage states for each structural type and each intensity level are computed in terms of damage ratio. Damage probability matrices (DPMs) and vulnerability curves are obtained for specific structural types. A comparison analysis is fulfilled between the produced and the existing vulnerability models.
基金This study was financially supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0207,GML2019ZD0208)the China Geological Survey Program(DD20191007).
文摘The South China Sea(SCS)is the hotspot of geological scientific research and nature resource exploration and development due to the potential for enormous hydrocarbon resource development and a complex formation and evolution process.The SCS has experienced complex geological processes including continental lithospheric breakup,seafloor spreading and oceanic crust subduction,which leads debates for decades.However,there are still no clear answers regarding to the following aspects:the crustal and Moho structure,the structure of the continent-ocean transition zone,the formation and evolution process and geodynamic mechanism,and deep processes and their coupling relationships with the petroliferous basins in the SCS.Under the guidance of the“Deep-Earth”science and technology innovation strategy of the Ministry of Natural Resources,deep structural and comprehensive geological research are carried out in the SCS.Geophysical investigations such as long array-large volume deep reflection seismic,gravity,magnetism and ocean bottom seismometer are carried out.The authors proposed that joint gravitymagnetic-seismic inversion should be used to obtain deep crustal information in the SCS and construct high resolution deep structural sections in different regions of the SCS.This paper systematically interpreted the formation and evolution of the SCS and explored the coupling relationship between deep structure and evolution of Mesozoic-Cenozoic basins in the SCS.It is of great significance for promoting the geosystem scientific research and resource exploration of the SCS.