Dense array seismology, which is characterized by large number, densely deployed autonomous geophone/seismographs, has received great concerns worldwide recently, especially after the great success of dense array in L...Dense array seismology, which is characterized by large number, densely deployed autonomous geophone/seismographs, has received great concerns worldwide recently, especially after the great success of dense array in Long Beach. One of the biggest curiosity is that if the great success in Long Beach is replicable in China. Hence, we analyze the seismic records from a dense array in Binchuan basin, Yunnan province, which consists of three-component short-period seismographs of three most common domestic models. The Binchuan basin is located near the intersection between the Chenghai-Binchuan fault and the Red River fault,with the latter being the major fault accommodating significant tectonic deformation resulting from eastern extrusion of the Tibetan plateau. Both faults pose serious seismic threats to local residents in Binchuan basin. Basinrange differences, faults, local earthquakes, and a Fixed Airgun Seismic Transmitting Station(FASTS), make the Binchuan basin a perfect experiment site for dense array experiment. The array is named Array of Binchuan(ABC)and the main target is imaging the shallow crustal structure,especially the structure of the basin. To examine the monitoring capability of ABC, we analyze the seismograms to check if they can reveal the basin, the most significant geological feature in the area. Power spectral density analysis,travel time and amplitude analysis of FASTS signals, and amplitude analysis of earthquakes and noise cross-correlation functions are used in the analysis. All the results show correlation with the basin and clear difference between basin and non-basin area. Therefore, the preliminary results support that the ABC has the potential to provide constraints on local structures.展开更多
Basin effect was first described following the analysis of seismic ground motion associated with the 1985 MW8.1 earthquake in Mexico.Basins affect the propagation of seismic waves through various mechanisms,and severa...Basin effect was first described following the analysis of seismic ground motion associated with the 1985 MW8.1 earthquake in Mexico.Basins affect the propagation of seismic waves through various mechanisms,and several unique phenomena,such as the basin edge effect,basin focusing effect,and basin-induced secondary waves,have been observed.Understanding and quantitatively predicting these phenomena are crucial for earthquake disaster reduction.Some pioneering studies in this field have proposed a quantitative relationship between the basin effect on ground motion and basin depth.Unfortunately,basin effect phenomena predicted using a model based only on basin depth exhibit large deviations from actual distributions,implying the severe shortcomings of single-parameter basin effect modeling.Quaternary sediments are thick and widely distributed in the Beijing-Tianjin-Hebei region.The seismic media inside and outside of this basin have significantly different physical properties,and the basin bottom forms an interface with strong seismic reflections.In this study,we established a three-dimensional structure model of the Quaternary sedimentary basin based on the velocity structure model of the North China Craton and used it to simulate the ground motion under a strong earthquake following the spectral element method,obtaining the spatial distribution characteristics of the ground motion amplification ratio throughout the basin.The back-propagation(BP)neural network algorithm was then introduced to establish a multi-parameter mathematical model for predicting ground motion amplification ratios,with the seismic source location,physical property ratio of the media inside and outside the basin,seismic wave frequency,and basin shape as the input parameters.We then examined the main factors influencing the amplification of seismic ground motion in basins based on the prediction results,and concluded that the main factors influencing the basin effect are basin shape and differences in the physical properties of media inside and outside the basin.展开更多
Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear an...Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear analytical model for Fuzhou Basin was established.The peak ground motion acceleration(PGA) and focusing effect with depth were analyzed.Meanwhile,the results by wave propagation of one-dimensional(1D) layered medium equivalent linearization method were added for contrast.The results show that:1) PGA at different depths are obviously amplified compared to the input ground motion,amplification effect of both funnel-shaped depression and upheaval areas(based on the shape of bedrock surface) present especially remarkable.The 2D results indicate that the PGA displays a non-monotonic decreasing with depth and a greater focusing effect of some particular layers,while the 1D results turn out that the PGA decreases with depth,except that PGA at few particular depth increases abruptly; 2) To the funnel-shaped depression areas,PGA amplification effect above 8 m depth shows relatively larger,to the upheaval areas,PGA amplification effect from 15 m to 25 m depth seems more significant.However,the regularities of the PGA amplification effect could hardly be found in the rest areas; 3) It appears a higher regression rate of PGA amplification coefficient with depth when under a smaller input motion; 4) The frequency spectral characteristic of input motion has noticeable effects on PGA amplification tendency.展开更多
The Yinggehai Basin is a strongly overpressured Cenozoic basin developed in the northern continental shelf of the South China Sea. The flow of overpressured fluids in this basin has given rise to strong effects on pet...The Yinggehai Basin is a strongly overpressured Cenozoic basin developed in the northern continental shelf of the South China Sea. The flow of overpressured fluids in this basin has given rise to strong effects on petroleum accumulation. (1) The overpressured fluid flow has enhanced the maturation of shallow-buried source rocks, which has caused the source rocks that would have remained immature under the conduction background to be mature for hydrocarbon generation. As a result, the overpressured fluid flow has increased the volume and interval of mature source rocks. (2) The overpressured fluid flow has strong extraction effects on the immature or low-mature source rocks in the shallow parts. This has increased, to some extent, the expulsion efficiency of the source rocks. More importantly, the extraction effects have strongly limited the effectiveness of biomarker parameters from oil and condensate in reflecting the source and maturity of the oil and gas. (3) The flow has caused the sandstones in the shallow parts to get into the late diagenesis stage, and significantly reduced the porosity and permeability of the sandstones. This study confirms that even in sedimentary basins in which no topography-driven groundwater flow systems have ever developed, the cross-formation migration of overpressured fluids and the resultant energy conduction and material exchange can significantly affect the thermal regime, source rock maturation and sandstone diagenesis. As a result, the effects of overpressured fluid flow must be taken into account in analyzing the mechanism of petroleum accumulation.展开更多
Based on multi-type,multi-temporal remote sensing data,we have monitored recent changes in cultivated land use and vegetation,in sandy areas and salinized desertification in the Green Corridor zone of the main channel...Based on multi-type,multi-temporal remote sensing data,we have monitored recent changes in cultivated land use and vegetation,in sandy areas and salinized desertification in the Green Corridor zone of the main channel of the Tarim River Basin.The results of our investigation show that the ecological environment in the Green Corridor of the main channel of the Tarim River Basin has conspicuously improved from 2002 to 2004.These improvements show up largely in such aspects as an increase in the rate of vegetation cover,a reduction in desertification land areas and a weakening in the intensity of sandy and the salinized land.On the other hand,the cultivated area in the Tarim River Basin significantly increased from 2002 to 2004.The rate of growth in cultivated areas during this period was significantly higher than that from 1999 to 2002.The increase in the use of irrigation resulting from the substantial increase in cultivated areas has a long-term potential restraining effect on the restoration of ecological functions of the Tarim River.展开更多
The characteristics and distribution of faults in Yinggehai basin discussed in this paper reveal the structural effects of the overpressure fluid expulsion. The rapid subsidence and mud rich intervals of the marine r...The characteristics and distribution of faults in Yinggehai basin discussed in this paper reveal the structural effects of the overpressure fluid expulsion. The rapid subsidence and mud rich intervals of the marine rocks dominate the formation of the overpressure systems and the enormous volumes of the overpressure fluids in the basin. Triggered by some faults, the overpressure fluids were expulsed rapidly from the overpressure compartments to form a series of diapirs in the basin, resulting in the dense fractures or faults and folds in the limbs of diapirs. These fractures and faults provided the migration pathway for the vertical flow of hydrocarbons, so that the gas fields arising from this process might migrate upwards to the sandstone reservoir. Therefore, the hydrocarbon accumulations are usually located in the upper parts of diapiric structures.展开更多
In the Upper Silesian Coal Basin(USCB),coal seams are exploited under progressively more difficult geological and mining conditions(greater depth,higher horizontal stress,more frequent occurrence of competent rock lay...In the Upper Silesian Coal Basin(USCB),coal seams are exploited under progressively more difficult geological and mining conditions(greater depth,higher horizontal stress,more frequent occurrence of competent rock layers,etc.).Mining depth,dislocations and mining remnants in coal seams are the most important factors responsible for the occurrence of rockburst hazards.Longwall mining next to the mining edges of neighbouring coal seams is particularly disadvantageous.The levels of rockburst hazards are minimised via the use of rockburst prevention methods.One active prevention method is torpedo blasting in roof rocks.Torpedo blastings are performed in order to decrease local stress concentrations in rock masses and to fracture the roof rocks to prevent or minimise the impact of high-energy tremors on excavations.The estimation of the effectiveness of torpedo blasting is particularly important when mining is under difficult geological and mining conditions.Torpedo blasting is the main form of active rockburst prevention in the assigned colliery in the Polish part of the USCB.The effectiveness of blasting can be estimated using the seismic effect method,in which the seismic monitoring data and the mass of explosives are taken into consideration.The seismic effect method was developed in the Czech Republic and is always being used in collieries in the Czech part of the coal basin.Now,this method has been widely adopted for our selected colliery in the Polish part of the coal basin.The effectiveness of torpedo blastings in the faces and galleries of the assigned longwall in coal seam 506 has been estimated.The results show that the effectiveness of torpedo blastings for this longwall was significant in light of the seismic effect method,which corresponds to the in situ observations.The seismic effect method is regularly applied to estimating the blasting effectiveness in the selected colliery.展开更多
Complex superimposed basins exhibit multi-stage tectonic events and multi-stage reservoir formation; hydrocarbon reservoirs formed in the early stage have generally late-stage genesis characteristics after undergoing ...Complex superimposed basins exhibit multi-stage tectonic events and multi-stage reservoir formation; hydrocarbon reservoirs formed in the early stage have generally late-stage genesis characteristics after undergoing adjustment, reconstruction and destruction of later-stage multiple tectonic events. In this paper, this phenomenon is called the late-stage reservoir formation effect. The late-stage reservoir formation effect is a basic feature of oil and gas-forming reservoirs in complex superimposed basins, revealing not only multi-stage character, relevance and complexity of oil and gas- forming reservoirs in superimposed basins but also the importance of late-stage reservoir formation. Late-stage reservoir formation is not a basic feature of oil and gas forming reservoir in superimposed basins. Multi-stage reservoir formation only characterizes one aspect of oil and gas-forming reservoir in superimposed basins and does not represent fully the complexity of oil and gas-forming reservoir in superimposed basins. We suggest using ＂late-stage reservoir formation effect＂ to replace the ＂late-stage reservoir formation＂ concept to guide the exploration of complex reservoirs in superimposed basins. Under current geologic conditions, the late-stage reservoir formation effect is represented mainly by four basic forms： phase transformation, scale reconstruction, component variation and trap adjustment. The late-stage reservoir formation effect is produced by two kinds of geologic processes： first, the oil and gas retention function of various geologic thresholds （hydrocarbon expulsion threshold, hydrocarbon migration threshold, and hydrocarbon accumulating threshold） causes the actual time of oil and gas reservoir formation to be later than the time of generation of large amounts of hydrocarbon in a conventional sense, producing the late-stage reservoir formation effect; second, multiple types of tectonic events （continuously strong reconstruction, early-stage strong reconstruction, middle-stage strong reconstruction, late-stage strong reconstruction and long-term stable sedimentation） after oil and gas reservoir formation lead to adjustment, reconstruction and destruction of reservoirs formed earlier, and form new secondary hydrocarbon reservoirs due to the late-stage reservoir formation effect.展开更多
The safe basin of a forced softening Duffing oscillator is studiednumerically. The changes of safe basins are observed under bothstationary and nonstationary variations of the external excitationfrequency. The kind of...The safe basin of a forced softening Duffing oscillator is studiednumerically. The changes of safe basins are observed under bothstationary and nonstationary variations of the external excitationfrequency. The kind of nonstationary variations of the excitationfrequency can greatly change the erosion rate and the shape of thesafe basin. The other effects of nonstatinary variations on the safebasin are also discussed.展开更多
In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect proble...In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect problem in Karst regions of China. Here we quantitatively extracted five main factors influencing soil erosion, namely rainfall erosivity, soil erodibility, vegetative cover and management, soil and water conservation, and slope length and steepness. Regression relations were built between these factors and also the sediment transport modulus and drainage area, so as to initially analyze and discuss scale effects on sediment transport in the Wujiang River Basin(WRB). The size and extent of soil erosion influencing factors in the WRB were gauged from: Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM), precipitation data, land use, soil type and Normalized Difference Vegetation Index(NDVI) data from Global Inventory Modeling and Mapping Studies(GIMMS) or Advanced Very High Resolution Radiometer(AVHRR), and observed data from hydrometric stations. We find that scaling effects exist between the sediment transport modulus and the drainage area. Scaling effects are expressed after logarithmic transformation by a quadratic function regression relationship where the sediment transport modulus increases before decreasing, alongside changes in the drainage area. Among the five factors influencing soil erosion, slope length and steepness increases first and then decreases, alongside changes in the drainage area, and are the main factors determining the relationship between sediment transport modulus and drainage area. To eliminate the influence of scale effects on our results, we mapped the sediment yield modulus of the entire WRB, adopting a 1 000 km^2 standard area with a smaller fitting error for all sub-basins, and using the common Kriging interpolation method.展开更多
The influence of local site effects on seismic ground motions is an important issue in seismic hazard assessment and earthquake resistant design. Determining site effects in densely populated cities built on basins ca...The influence of local site effects on seismic ground motions is an important issue in seismic hazard assessment and earthquake resistant design. Determining site effects in densely populated cities built on basins can help to reduce the earthquake hazard. Site effects of Luoyang basin are estimated by the horizontal-to-vertical spectral ratio(HVSR) method using ambient noise records from a short-period dense array. The sites in Luoyang basin are sorted into three types according to the pattern of the HVSR curves. There are cases with a single clear peak, two clear peaks, and an unclear low frequency peak or multiple peaks, which correspond to there being one large impedance contrast interface, two large interfaces, and a moderate one beneath the sites, respectively. The site effects characterized by fundamental frequency from HVSR curves are affected by underlying sedimentary layers and depth of sedimentary basement. According to our results, the existence of thick sediment layer obviously lowers the fundamental frequency to the period range from 2 to 4 s in the downtown area of Luoyang city. The ground motion will amplify when through the sites and the buildings with height of 20–50 floors can resonate at the similar frequency domain. Site effects estimation using HVSR method from a short-period dense array is an effective technique in areas of moderate seismic risk where strong motion recordings are lacking, such as the Luoyang basin.展开更多
Co-seismic gas leakage usually occurs on the edge of seismic faults in petroliferous basins,and it may have an impact on the local environment,such as the greenhouse effect,which can cause thermal infrared brightness ...Co-seismic gas leakage usually occurs on the edge of seismic faults in petroliferous basins,and it may have an impact on the local environment,such as the greenhouse effect,which can cause thermal infrared brightness anomalies.Using wavelet transform and power spectrum estimation methods,we processed brightness temperature data from the Chinese geostationary meteorological satellite FY-C/E.We report similarities between the co-seismic thermal infrared brightness(CTIB)anomalies before,during and after earthquakes that occurred at the edges of the Sichuan,Tarim,Qaidam,and Junggar basins surrounding the North and East of the Qinghai–Tibet Plateau in western China.Additionally,in each petroliferous basin,the area of a single CTIB anomaly accounted for 50%to 100%of the basin area,and the spatial distribution similarities in the CTIB anomalies existed before,during and after these earthquakes.To better interpret the similarities,we developed a basin warming effect model based on geological structures and topography.The model suggests that in a petroliferous basin with a subsurface gas reservoir,gas leakage could strengthen with the increasing stress before,during,and even after an earthquake.The accumulation of these gases,such as the greenhouse gases CH4 and CO2,results in the CTIB anomalies.In addition,we conclude that the CTIB anomalies are strengthened by the high mountains(altitude^5000 m)around the basins and the basins’independent climatic conditions.This work provides a new perspective from which to understand the CTIB anomalies in petroliferous basins surrounding the North and East of the Qinghai–Tibet Plateau.展开更多
Influenced by the Indosinian Lincang granite,the level the natural radioactivity in the Lincang Basin is relatively high.This work deals with the determination of natural radioactivity of soil in this area by using th...Influenced by the Indosinian Lincang granite,the level the natural radioactivity in the Lincang Basin is relatively high.This work deals with the determination of natural radioactivity of soil in this area by using theγ-ray spectrometer.The specific activities of 2 26Ra, 238U, 232Th and 40K obtained were obviously greater than the average values of these nuclides countrywide and worldwide,which were 53.4(from 38.7 to 62.8),161.2(from 127.3 to 211.7),120.9(from 106.5 to 140.6)and 632.2(from 521.7 to 707.5)Bq/kg.Based on the research data,the level of natural radioactivity of the granite was high,which impacts and provides a good source of soil radioactivity in the study area.To assess the radiological hazard of the natural radioactivity in soil,the γ-absorbed dose rate and annual effective dose rate were calculated.The results show that,although the γ-absorbed dose rate in the study area is a little high,the annual effective dose rate is lower than the recommended value.So the Lincang Basin is safe with respect to radiological level and its living environment is not affected.展开更多
This work aims to reveal the evolution of the porosity in the Triassic Yanchang Formation tight sandstone reservoir of the Xifeng-Ansai area of Ordos Basin. Based on destructive diagenesis （compaction and cementation...This work aims to reveal the evolution of the porosity in the Triassic Yanchang Formation tight sandstone reservoir of the Xifeng-Ansai area of Ordos Basin. Based on destructive diagenesis （compaction and cementation） and constructive diagenesis （dissolution） of sandstone reservoirs, this study analyzed the diagenesis characteristics of the tight sandstone reservoirs in this area, and discussed the relationship between sandstone diagenesis and porosity evolution in combination with present porosity profile characteristics of sandstone reservoir. The effect simulation principle was employed for the mathematical derivation and simulation of the evolution of porosity in the Yanchang Formation tight sandstone reservoirs. The result shows that compaction always occurs in tight sandstone reservoirs in the Yanchang Formation, and cementation occurs when the burial depth increases to a certain value and remains ever since. Dissolution occurs only at a certain stage of the evolution with window features. In the corresponding present porosity profile, diagenesis is characterized by segmentation. From the shallow to the deep, compaction, compaction, cementation and dissolution, compaction and cementation occur successively. Therefore, the evolution of sandstone porosity can be divided into normal compaction section, acidification and incremental porosity section, and normal compaction section after dissolution. The results show that the evolution of sandstone porosity can be decomposed into porosity reduction model and porosity increase model. The superposition of the two models at the same depth in the three stages or in the same geological time can constitute the evolution simulation of the total porosity in sandstone reservoirs. By simulating the evolution of sandstone reservoir porosity of the eighth member in Xifeng area and the sixth member in Ansai area, it shows that they are similar in the evolution process and trend. The difference is caused by the regional uplift or subsidence and burial depth.展开更多
Carbon isotopes of natural gases are controlled not only by source and mature effect, but also by accumulating (leakage and mixing) effect. The gases, distributed in the three paleo\|uplifts, Tazhong, Tabei and Bachu ...Carbon isotopes of natural gases are controlled not only by source and mature effect, but also by accumulating (leakage and mixing) effect. The gases, distributed in the three paleo\|uplifts, Tazhong, Tabei and Bachu in the Tarim Basin, are generated mainly from Cambrian and Lower Ordovician hydrocarbon\|source rocks. Being under good preservation conditions, gas pools in the Tazhong region experienced a long accumulation period, resulting in a successive gas accumulation region in this region. The gas carbon isotope values are more negative than those in other regions because of the strong accumulating effect. The Tabei and Mazhatage regions have poor preservation conditions, the gas pools are formed in a short accumulation period, and the gas carbon isotope values are more positive. This is called the transition\|stage gas accumulation region. Because of involvement of low mature gas, even biogenic gas from Upper\|Middle Ordovician, some gas in Ordovician reservoirs on the northern slope of the Tazhong uplift is characterized by much more negative \{δ\{\}\+\{13\}C\-1\}. The \{δ\{\}\+\{13\}C\-2\}\|\{δ\{\}\+\{13\}C\-1\} value is an effective index to measure the gas maturity of the main body in a gas pool. Combining \{δ\{\}\+\{13\}C\-2\}\|\{δ\{\}\+\{13\}C\-1\} with \{δ\{\}\+\{13\}C\-1\} and \{δ\{\}\+\{13\}C\-2\}, the effects described above can be explained very well. Results of our study show that the gas maturity for the Mazhatage region is the highest in the craton basin, followed by Tabei. Gases in the Tazhong area are high\|over mature gases though the gas carbon isotope values are highly negative.展开更多
Many of the sedimentary basins in western China were formed through the superposition and compounding of at least two previously developed sedimentary basins and in general they can be termed as complex superimposed b...Many of the sedimentary basins in western China were formed through the superposition and compounding of at least two previously developed sedimentary basins and in general they can be termed as complex superimposed basins. The distinct differences between these basins and monotype basins are their discontinuous stratigraphic sedimentation, stratigraphic structure and stratigraphic stress-strain action over geological history. Based on the correlation of chronological age on structural sections, superimposed basins can be divided into five types in this study： （1） continuous sedimentation type superimposed basins, （2） middle and late stratigraphic superimposed basins, （3） early and late stratigraphic superimposed basins, （4） early and middle stratigraphic superimposed basins, and （5） long-term exposed superimposed basins. Multiple source-reservoir-caprock assemblages have developed in such basins. In addition, multi-stage hydrocarbon generation and expulsion, multiple sources, polycyclic hydrocarbon accumulation and multiple-type hydrocarbon reservoirs adjustment, reformation and destruction have occurred in these basins. The complex reservoirs that have been discovered widely in the superimposed basins to date have remarkably different geologic features from primary reservoirs, and the root causes of this are folding, denudation and the fracture effect caused by multiphase tectonic events in the superimposed basins as well as associated seepage, diffusion, spilling, oxidation, degradation and cracking. Based on their genesis characteristics, complex reservoirs are divided into five categories： （1） primary reservoirs, （2） trap adjustment type reservoirs, （3） component variant reservoirs, （4） phase conversion type reservoirs and （5） scale-reformed reservoirs.展开更多
As the structural body related to temporal-spatial evolution and tectonic dynamic system, the orogenic belt and basin are not only dependent on each other in space but also closely related with each other in terms of ...As the structural body related to temporal-spatial evolution and tectonic dynamic system, the orogenic belt and basin are not only dependent on each other in space but also closely related with each other in terms of infrastructure, matter transference and dynamic mechanisms. By using apatite fission-track method, the authors firstly analyze the uplift and denudation ratios of the Qinling-Dabie orogenic belt, and by using tectonically deformed combination analysis and tectonic-thermal simulation the main geological occurrences are also illustrated. It is found that there must have had multi-phase differential uplift and denudation phenomena in the Qinling-Dabie orogenic belt during the Mesozoic-Cenozoic. Then, the regional evolution pattern of qualitative and quantitative denudation process is obtained during the post-orogenic period. On the basis of summarizing evolution process of the basin-range system in the Qinling-Dabie orogenic belt during the Mesozoic-Cenozoic and its effects on regional environment, the influence of evolution process on geomorphologic landscapes change, water system vicissitude, eco-environment succession and drainage basin system evolution is discussed.展开更多
Constructed stormwater infiltration basins have been broad applied in urban areas in terms of stormwater disposal and compensation of reduced groundwater recharge. However, stormwater derived from sediments accumulati...Constructed stormwater infiltration basins have been broad applied in urban areas in terms of stormwater disposal and compensation of reduced groundwater recharge. However, stormwater derived from sediments accumulating in infiltration beds may act as a source of dissolved contaminants for groundwater. Concentrations of DO, NO3-N, NO2^--N, NH4^＋-N and PO4^3--P were monitored at multiple depth with time. The results showed that the occurrence of denitrificarion was restrained by sediments in term of no invertebrates. Under the conditions of invertebrates inoculated, the concentrations of DO, NO^3--N, NO2^＋-N, NH4^＋-N and PO4^3＋-P varied respectively with time and the occurrence of nitrification and mobilizing nitrate in the sediment. It is concluded that there exist the invertebrate activities such as building tubes and galleries and excreting faecal pellet which may increase water dispersion and enhance accessibility of nutrient, and stimulate microbial process effected in the sediment. Besides, the natural death and rot of worms were also found to be important factors of the invertebrate activities.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41674058,41790463)Chen Yong Academician Workstation in Yunnan province(Grant No.2014IC007)
文摘Dense array seismology, which is characterized by large number, densely deployed autonomous geophone/seismographs, has received great concerns worldwide recently, especially after the great success of dense array in Long Beach. One of the biggest curiosity is that if the great success in Long Beach is replicable in China. Hence, we analyze the seismic records from a dense array in Binchuan basin, Yunnan province, which consists of three-component short-period seismographs of three most common domestic models. The Binchuan basin is located near the intersection between the Chenghai-Binchuan fault and the Red River fault,with the latter being the major fault accommodating significant tectonic deformation resulting from eastern extrusion of the Tibetan plateau. Both faults pose serious seismic threats to local residents in Binchuan basin. Basinrange differences, faults, local earthquakes, and a Fixed Airgun Seismic Transmitting Station(FASTS), make the Binchuan basin a perfect experiment site for dense array experiment. The array is named Array of Binchuan(ABC)and the main target is imaging the shallow crustal structure,especially the structure of the basin. To examine the monitoring capability of ABC, we analyze the seismograms to check if they can reveal the basin, the most significant geological feature in the area. Power spectral density analysis,travel time and amplitude analysis of FASTS signals, and amplitude analysis of earthquakes and noise cross-correlation functions are used in the analysis. All the results show correlation with the basin and clear difference between basin and non-basin area. Therefore, the preliminary results support that the ABC has the potential to provide constraints on local structures.
基金funded by the General Program of the National Natural Science Foundation of China(No.42174070)the General Program of the Beijing Natural Science Foundation(No.8222035).
文摘Basin effect was first described following the analysis of seismic ground motion associated with the 1985 MW8.1 earthquake in Mexico.Basins affect the propagation of seismic waves through various mechanisms,and several unique phenomena,such as the basin edge effect,basin focusing effect,and basin-induced secondary waves,have been observed.Understanding and quantitatively predicting these phenomena are crucial for earthquake disaster reduction.Some pioneering studies in this field have proposed a quantitative relationship between the basin effect on ground motion and basin depth.Unfortunately,basin effect phenomena predicted using a model based only on basin depth exhibit large deviations from actual distributions,implying the severe shortcomings of single-parameter basin effect modeling.Quaternary sediments are thick and widely distributed in the Beijing-Tianjin-Hebei region.The seismic media inside and outside of this basin have significantly different physical properties,and the basin bottom forms an interface with strong seismic reflections.In this study,we established a three-dimensional structure model of the Quaternary sedimentary basin based on the velocity structure model of the North China Craton and used it to simulate the ground motion under a strong earthquake following the spectral element method,obtaining the spatial distribution characteristics of the ground motion amplification ratio throughout the basin.The back-propagation(BP)neural network algorithm was then introduced to establish a multi-parameter mathematical model for predicting ground motion amplification ratios,with the seismic source location,physical property ratio of the media inside and outside the basin,seismic wave frequency,and basin shape as the input parameters.We then examined the main factors influencing the amplification of seismic ground motion in basins based on the prediction results,and concluded that the main factors influencing the basin effect are basin shape and differences in the physical properties of media inside and outside the basin.
基金Project(2011CB013601) supported by the National Basic Research Program of ChinaProject(51378258) supported by the National Natural Science Foundation of China
文摘Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear analytical model for Fuzhou Basin was established.The peak ground motion acceleration(PGA) and focusing effect with depth were analyzed.Meanwhile,the results by wave propagation of one-dimensional(1D) layered medium equivalent linearization method were added for contrast.The results show that:1) PGA at different depths are obviously amplified compared to the input ground motion,amplification effect of both funnel-shaped depression and upheaval areas(based on the shape of bedrock surface) present especially remarkable.The 2D results indicate that the PGA displays a non-monotonic decreasing with depth and a greater focusing effect of some particular layers,while the 1D results turn out that the PGA decreases with depth,except that PGA at few particular depth increases abruptly; 2) To the funnel-shaped depression areas,PGA amplification effect above 8 m depth shows relatively larger,to the upheaval areas,PGA amplification effect from 15 m to 25 m depth seems more significant.However,the regularities of the PGA amplification effect could hardly be found in the rest areas; 3) It appears a higher regression rate of PGA amplification coefficient with depth when under a smaller input motion; 4) The frequency spectral characteristic of input motion has noticeable effects on PGA amplification tendency.
基金This research was supported by the National Natural Science Foundation of China(grants 401 25008 and 40238059).
文摘The Yinggehai Basin is a strongly overpressured Cenozoic basin developed in the northern continental shelf of the South China Sea. The flow of overpressured fluids in this basin has given rise to strong effects on petroleum accumulation. (1) The overpressured fluid flow has enhanced the maturation of shallow-buried source rocks, which has caused the source rocks that would have remained immature under the conduction background to be mature for hydrocarbon generation. As a result, the overpressured fluid flow has increased the volume and interval of mature source rocks. (2) The overpressured fluid flow has strong extraction effects on the immature or low-mature source rocks in the shallow parts. This has increased, to some extent, the expulsion efficiency of the source rocks. More importantly, the extraction effects have strongly limited the effectiveness of biomarker parameters from oil and condensate in reflecting the source and maturity of the oil and gas. (3) The flow has caused the sandstones in the shallow parts to get into the late diagenesis stage, and significantly reduced the porosity and permeability of the sandstones. This study confirms that even in sedimentary basins in which no topography-driven groundwater flow systems have ever developed, the cross-formation migration of overpressured fluids and the resultant energy conduction and material exchange can significantly affect the thermal regime, source rock maturation and sandstone diagenesis. As a result, the effects of overpressured fluid flow must be taken into account in analyzing the mechanism of petroleum accumulation.
基金Financial support for this work was provided by the National Natural Science Foundation of China (No. 41040011)the Fun-damental Research Funds for the Central Universities (No.CHD2010JC103)
文摘Based on multi-type,multi-temporal remote sensing data,we have monitored recent changes in cultivated land use and vegetation,in sandy areas and salinized desertification in the Green Corridor zone of the main channel of the Tarim River Basin.The results of our investigation show that the ecological environment in the Green Corridor of the main channel of the Tarim River Basin has conspicuously improved from 2002 to 2004.These improvements show up largely in such aspects as an increase in the rate of vegetation cover,a reduction in desertification land areas and a weakening in the intensity of sandy and the salinized land.On the other hand,the cultivated area in the Tarim River Basin significantly increased from 2002 to 2004.The rate of growth in cultivated areas during this period was significantly higher than that from 1999 to 2002.The increase in the use of irrigation resulting from the substantial increase in cultivated areas has a long-term potential restraining effect on the restoration of ecological functions of the Tarim River.
文摘The characteristics and distribution of faults in Yinggehai basin discussed in this paper reveal the structural effects of the overpressure fluid expulsion. The rapid subsidence and mud rich intervals of the marine rocks dominate the formation of the overpressure systems and the enormous volumes of the overpressure fluids in the basin. Triggered by some faults, the overpressure fluids were expulsed rapidly from the overpressure compartments to form a series of diapirs in the basin, resulting in the dense fractures or faults and folds in the limbs of diapirs. These fractures and faults provided the migration pathway for the vertical flow of hydrocarbons, so that the gas fields arising from this process might migrate upwards to the sandstone reservoir. Therefore, the hydrocarbon accumulations are usually located in the upper parts of diapiric structures.
文摘In the Upper Silesian Coal Basin(USCB),coal seams are exploited under progressively more difficult geological and mining conditions(greater depth,higher horizontal stress,more frequent occurrence of competent rock layers,etc.).Mining depth,dislocations and mining remnants in coal seams are the most important factors responsible for the occurrence of rockburst hazards.Longwall mining next to the mining edges of neighbouring coal seams is particularly disadvantageous.The levels of rockburst hazards are minimised via the use of rockburst prevention methods.One active prevention method is torpedo blasting in roof rocks.Torpedo blastings are performed in order to decrease local stress concentrations in rock masses and to fracture the roof rocks to prevent or minimise the impact of high-energy tremors on excavations.The estimation of the effectiveness of torpedo blasting is particularly important when mining is under difficult geological and mining conditions.Torpedo blasting is the main form of active rockburst prevention in the assigned colliery in the Polish part of the USCB.The effectiveness of blasting can be estimated using the seismic effect method,in which the seismic monitoring data and the mass of explosives are taken into consideration.The seismic effect method was developed in the Czech Republic and is always being used in collieries in the Czech part of the coal basin.Now,this method has been widely adopted for our selected colliery in the Polish part of the coal basin.The effectiveness of torpedo blastings in the faces and galleries of the assigned longwall in coal seam 506 has been estimated.The results show that the effectiveness of torpedo blastings for this longwall was significant in light of the seismic effect method,which corresponds to the in situ observations.The seismic effect method is regularly applied to estimating the blasting effectiveness in the selected colliery.
基金State Key Basic Research "973" Program (2006CB202308) for funding this research
文摘Complex superimposed basins exhibit multi-stage tectonic events and multi-stage reservoir formation; hydrocarbon reservoirs formed in the early stage have generally late-stage genesis characteristics after undergoing adjustment, reconstruction and destruction of later-stage multiple tectonic events. In this paper, this phenomenon is called the late-stage reservoir formation effect. The late-stage reservoir formation effect is a basic feature of oil and gas-forming reservoirs in complex superimposed basins, revealing not only multi-stage character, relevance and complexity of oil and gas- forming reservoirs in superimposed basins but also the importance of late-stage reservoir formation. Late-stage reservoir formation is not a basic feature of oil and gas forming reservoir in superimposed basins. Multi-stage reservoir formation only characterizes one aspect of oil and gas-forming reservoir in superimposed basins and does not represent fully the complexity of oil and gas-forming reservoir in superimposed basins. We suggest using ＂late-stage reservoir formation effect＂ to replace the ＂late-stage reservoir formation＂ concept to guide the exploration of complex reservoirs in superimposed basins. Under current geologic conditions, the late-stage reservoir formation effect is represented mainly by four basic forms： phase transformation, scale reconstruction, component variation and trap adjustment. The late-stage reservoir formation effect is produced by two kinds of geologic processes： first, the oil and gas retention function of various geologic thresholds （hydrocarbon expulsion threshold, hydrocarbon migration threshold, and hydrocarbon accumulating threshold） causes the actual time of oil and gas reservoir formation to be later than the time of generation of large amounts of hydrocarbon in a conventional sense, producing the late-stage reservoir formation effect; second, multiple types of tectonic events （continuously strong reconstruction, early-stage strong reconstruction, middle-stage strong reconstruction, late-stage strong reconstruction and long-term stable sedimentation） after oil and gas reservoir formation lead to adjustment, reconstruction and destruction of reservoirs formed earlier, and form new secondary hydrocarbon reservoirs due to the late-stage reservoir formation effect.
基金the National Natural Science Foundationthe Aviation S■ loundationthe Doctoral Training Foundation of China
文摘The safe basin of a forced softening Duffing oscillator is studiednumerically. The changes of safe basins are observed under bothstationary and nonstationary variations of the external excitationfrequency. The kind of nonstationary variations of the excitationfrequency can greatly change the erosion rate and the shape of thesafe basin. The other effects of nonstatinary variations on the safebasin are also discussed.
基金generously supported by Project of National Natural Science Foundation of China (41641011)National Geology and Mineral Resources Survey and Assessment Program (DDT0160087)
文摘In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect problem in Karst regions of China. Here we quantitatively extracted five main factors influencing soil erosion, namely rainfall erosivity, soil erodibility, vegetative cover and management, soil and water conservation, and slope length and steepness. Regression relations were built between these factors and also the sediment transport modulus and drainage area, so as to initially analyze and discuss scale effects on sediment transport in the Wujiang River Basin(WRB). The size and extent of soil erosion influencing factors in the WRB were gauged from: Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM), precipitation data, land use, soil type and Normalized Difference Vegetation Index(NDVI) data from Global Inventory Modeling and Mapping Studies(GIMMS) or Advanced Very High Resolution Radiometer(AVHRR), and observed data from hydrometric stations. We find that scaling effects exist between the sediment transport modulus and the drainage area. Scaling effects are expressed after logarithmic transformation by a quadratic function regression relationship where the sediment transport modulus increases before decreasing, alongside changes in the drainage area. Among the five factors influencing soil erosion, slope length and steepness increases first and then decreases, alongside changes in the drainage area, and are the main factors determining the relationship between sediment transport modulus and drainage area. To eliminate the influence of scale effects on our results, we mapped the sediment yield modulus of the entire WRB, adopting a 1 000 km^2 standard area with a smaller fitting error for all sub-basins, and using the common Kriging interpolation method.
基金funded by the National Key R&D Program of China(No.2017YFC1500202)supported by the National Natural Science Foundation of China(No.41604048)China Earthquake Science Experiment(No.2016CESE0103)
文摘The influence of local site effects on seismic ground motions is an important issue in seismic hazard assessment and earthquake resistant design. Determining site effects in densely populated cities built on basins can help to reduce the earthquake hazard. Site effects of Luoyang basin are estimated by the horizontal-to-vertical spectral ratio(HVSR) method using ambient noise records from a short-period dense array. The sites in Luoyang basin are sorted into three types according to the pattern of the HVSR curves. There are cases with a single clear peak, two clear peaks, and an unclear low frequency peak or multiple peaks, which correspond to there being one large impedance contrast interface, two large interfaces, and a moderate one beneath the sites, respectively. The site effects characterized by fundamental frequency from HVSR curves are affected by underlying sedimentary layers and depth of sedimentary basement. According to our results, the existence of thick sediment layer obviously lowers the fundamental frequency to the period range from 2 to 4 s in the downtown area of Luoyang city. The ground motion will amplify when through the sites and the buildings with height of 20–50 floors can resonate at the similar frequency domain. Site effects estimation using HVSR method from a short-period dense array is an effective technique in areas of moderate seismic risk where strong motion recordings are lacking, such as the Luoyang basin.
基金the research project of China Earthquake Administration—Earthquake Science and Technology Star Fire Plan(XH2018035Y)Seismic Regime Tracking Project of CEA(2020010410).
文摘Co-seismic gas leakage usually occurs on the edge of seismic faults in petroliferous basins,and it may have an impact on the local environment,such as the greenhouse effect,which can cause thermal infrared brightness anomalies.Using wavelet transform and power spectrum estimation methods,we processed brightness temperature data from the Chinese geostationary meteorological satellite FY-C/E.We report similarities between the co-seismic thermal infrared brightness(CTIB)anomalies before,during and after earthquakes that occurred at the edges of the Sichuan,Tarim,Qaidam,and Junggar basins surrounding the North and East of the Qinghai–Tibet Plateau in western China.Additionally,in each petroliferous basin,the area of a single CTIB anomaly accounted for 50%to 100%of the basin area,and the spatial distribution similarities in the CTIB anomalies existed before,during and after these earthquakes.To better interpret the similarities,we developed a basin warming effect model based on geological structures and topography.The model suggests that in a petroliferous basin with a subsurface gas reservoir,gas leakage could strengthen with the increasing stress before,during,and even after an earthquake.The accumulation of these gases,such as the greenhouse gases CH4 and CO2,results in the CTIB anomalies.In addition,we conclude that the CTIB anomalies are strengthened by the high mountains(altitude^5000 m)around the basins and the basins’independent climatic conditions.This work provides a new perspective from which to understand the CTIB anomalies in petroliferous basins surrounding the North and East of the Qinghai–Tibet Plateau.
文摘Influenced by the Indosinian Lincang granite,the level the natural radioactivity in the Lincang Basin is relatively high.This work deals with the determination of natural radioactivity of soil in this area by using theγ-ray spectrometer.The specific activities of 2 26Ra, 238U, 232Th and 40K obtained were obviously greater than the average values of these nuclides countrywide and worldwide,which were 53.4(from 38.7 to 62.8),161.2(from 127.3 to 211.7),120.9(from 106.5 to 140.6)and 632.2(from 521.7 to 707.5)Bq/kg.Based on the research data,the level of natural radioactivity of the granite was high,which impacts and provides a good source of soil radioactivity in the study area.To assess the radiological hazard of the natural radioactivity in soil,the γ-absorbed dose rate and annual effective dose rate were calculated.The results show that,although the γ-absorbed dose rate in the study area is a little high,the annual effective dose rate is lower than the recommended value.So the Lincang Basin is safe with respect to radiological level and its living environment is not affected.
基金financially supported by the National Natural Science Foundation of China (grant No.41502147)Sichuan Province University Scientific Innovation Team Construction Project (USITCP)+1 种基金the Yong Scholars Development Fund of SWPU (grant No.201499010089)the National Science and Technology Major Project (grant No.2011ZX05001-001-04)
文摘This work aims to reveal the evolution of the porosity in the Triassic Yanchang Formation tight sandstone reservoir of the Xifeng-Ansai area of Ordos Basin. Based on destructive diagenesis （compaction and cementation） and constructive diagenesis （dissolution） of sandstone reservoirs, this study analyzed the diagenesis characteristics of the tight sandstone reservoirs in this area, and discussed the relationship between sandstone diagenesis and porosity evolution in combination with present porosity profile characteristics of sandstone reservoir. The effect simulation principle was employed for the mathematical derivation and simulation of the evolution of porosity in the Yanchang Formation tight sandstone reservoirs. The result shows that compaction always occurs in tight sandstone reservoirs in the Yanchang Formation, and cementation occurs when the burial depth increases to a certain value and remains ever since. Dissolution occurs only at a certain stage of the evolution with window features. In the corresponding present porosity profile, diagenesis is characterized by segmentation. From the shallow to the deep, compaction, compaction, cementation and dissolution, compaction and cementation occur successively. Therefore, the evolution of sandstone porosity can be divided into normal compaction section, acidification and incremental porosity section, and normal compaction section after dissolution. The results show that the evolution of sandstone porosity can be decomposed into porosity reduction model and porosity increase model. The superposition of the two models at the same depth in the three stages or in the same geological time can constitute the evolution simulation of the total porosity in sandstone reservoirs. By simulating the evolution of sandstone reservoir porosity of the eighth member in Xifeng area and the sixth member in Ansai area, it shows that they are similar in the evolution process and trend. The difference is caused by the regional uplift or subsidence and burial depth.
文摘Carbon isotopes of natural gases are controlled not only by source and mature effect, but also by accumulating (leakage and mixing) effect. The gases, distributed in the three paleo\|uplifts, Tazhong, Tabei and Bachu in the Tarim Basin, are generated mainly from Cambrian and Lower Ordovician hydrocarbon\|source rocks. Being under good preservation conditions, gas pools in the Tazhong region experienced a long accumulation period, resulting in a successive gas accumulation region in this region. The gas carbon isotope values are more negative than those in other regions because of the strong accumulating effect. The Tabei and Mazhatage regions have poor preservation conditions, the gas pools are formed in a short accumulation period, and the gas carbon isotope values are more positive. This is called the transition\|stage gas accumulation region. Because of involvement of low mature gas, even biogenic gas from Upper\|Middle Ordovician, some gas in Ordovician reservoirs on the northern slope of the Tazhong uplift is characterized by much more negative \{δ\{\}\+\{13\}C\-1\}. The \{δ\{\}\+\{13\}C\-2\}\|\{δ\{\}\+\{13\}C\-1\} value is an effective index to measure the gas maturity of the main body in a gas pool. Combining \{δ\{\}\+\{13\}C\-2\}\|\{δ\{\}\+\{13\}C\-1\} with \{δ\{\}\+\{13\}C\-1\} and \{δ\{\}\+\{13\}C\-2\}, the effects described above can be explained very well. Results of our study show that the gas maturity for the Mazhatage region is the highest in the craton basin, followed by Tabei. Gases in the Tazhong area are high\|over mature gases though the gas carbon isotope values are highly negative.
基金the National Key Fundamental Research Plan "973" Project(2006CB202308) for funds for this paper
文摘Many of the sedimentary basins in western China were formed through the superposition and compounding of at least two previously developed sedimentary basins and in general they can be termed as complex superimposed basins. The distinct differences between these basins and monotype basins are their discontinuous stratigraphic sedimentation, stratigraphic structure and stratigraphic stress-strain action over geological history. Based on the correlation of chronological age on structural sections, superimposed basins can be divided into five types in this study： （1） continuous sedimentation type superimposed basins, （2） middle and late stratigraphic superimposed basins, （3） early and late stratigraphic superimposed basins, （4） early and middle stratigraphic superimposed basins, and （5） long-term exposed superimposed basins. Multiple source-reservoir-caprock assemblages have developed in such basins. In addition, multi-stage hydrocarbon generation and expulsion, multiple sources, polycyclic hydrocarbon accumulation and multiple-type hydrocarbon reservoirs adjustment, reformation and destruction have occurred in these basins. The complex reservoirs that have been discovered widely in the superimposed basins to date have remarkably different geologic features from primary reservoirs, and the root causes of this are folding, denudation and the fracture effect caused by multiphase tectonic events in the superimposed basins as well as associated seepage, diffusion, spilling, oxidation, degradation and cracking. Based on their genesis characteristics, complex reservoirs are divided into five categories： （1） primary reservoirs, （2） trap adjustment type reservoirs, （3） component variant reservoirs, （4） phase conversion type reservoirs and （5） scale-reformed reservoirs.
文摘As the structural body related to temporal-spatial evolution and tectonic dynamic system, the orogenic belt and basin are not only dependent on each other in space but also closely related with each other in terms of infrastructure, matter transference and dynamic mechanisms. By using apatite fission-track method, the authors firstly analyze the uplift and denudation ratios of the Qinling-Dabie orogenic belt, and by using tectonically deformed combination analysis and tectonic-thermal simulation the main geological occurrences are also illustrated. It is found that there must have had multi-phase differential uplift and denudation phenomena in the Qinling-Dabie orogenic belt during the Mesozoic-Cenozoic. Then, the regional evolution pattern of qualitative and quantitative denudation process is obtained during the post-orogenic period. On the basis of summarizing evolution process of the basin-range system in the Qinling-Dabie orogenic belt during the Mesozoic-Cenozoic and its effects on regional environment, the influence of evolution process on geomorphologic landscapes change, water system vicissitude, eco-environment succession and drainage basin system evolution is discussed.
文摘Constructed stormwater infiltration basins have been broad applied in urban areas in terms of stormwater disposal and compensation of reduced groundwater recharge. However, stormwater derived from sediments accumulating in infiltration beds may act as a source of dissolved contaminants for groundwater. Concentrations of DO, NO3-N, NO2^--N, NH4^＋-N and PO4^3--P were monitored at multiple depth with time. The results showed that the occurrence of denitrificarion was restrained by sediments in term of no invertebrates. Under the conditions of invertebrates inoculated, the concentrations of DO, NO^3--N, NO2^＋-N, NH4^＋-N and PO4^3＋-P varied respectively with time and the occurrence of nitrification and mobilizing nitrate in the sediment. It is concluded that there exist the invertebrate activities such as building tubes and galleries and excreting faecal pellet which may increase water dispersion and enhance accessibility of nutrient, and stimulate microbial process effected in the sediment. Besides, the natural death and rot of worms were also found to be important factors of the invertebrate activities.
