Through reviewing the flow theory’s birth and development history in underground porous media and contrasting the mechanics of underground fluids and mechanics of viscous fluids, this paper points out the main facto...Through reviewing the flow theory’s birth and development history in underground porous media and contrasting the mechanics of underground fluids and mechanics of viscous fluids, this paper points out the main factors, which affect the development of the theory on oil and gas porous flow. The development law and development route of the mechanics of fluids in porous media are also summarized in this paper.展开更多
Present granite landform characteristics and distribution are the integrated result of climate, tectonics and lithology. Various types of granite landforms in China signify climate zonality and differential vertical m...Present granite landform characteristics and distribution are the integrated result of climate, tectonics and lithology. Various types of granite landforms in China signify climate zonality and differential vertical movement of earth surface, while published research results on Chinese granite landforms are very rare, especially in international journals. Based on the process analysis of chemical weathering and physical disintegration, four granite landform regions in China are classified according to the present climate regime. On the Tibetan Plateau, the cold and freezing climate induced periglacial landscapes; the northeast region is characterized by physical disintegration and low round mounds are widespread; in the northwest region controlled by arid climate, wind-carved minor landscapes are extremely prominent. The most spectacular granite landscapes in China are presented in southeast as a result of Iongtime chemical weathering under humid and warm conditions, as well as the differential uplift after Neogene. Correlating the weathering crust in southern China, Tibetan Plateau and India, a possible unified planation surface in Neogene is proposed. With corestones as indicators of original weathering front, the differential uplift extent of dissected planation surfaces can be estimated. At least three landforms implying uplift can be identified in southeastern China, with elevations of 300-400 m, 2000 m and 3600 m above the sea level respectively.展开更多
The prominent types of Danxia landform in Fangyan include enclosed valleys, mesas, peaks, stone columns and grooves etc. Their spatial combinations have regular configurations along the northwest–southeast direction:...The prominent types of Danxia landform in Fangyan include enclosed valleys, mesas, peaks, stone columns and grooves etc. Their spatial combinations have regular configurations along the northwest–southeast direction: typical grooves and caves are located in the northwestern Wufengshuyuan mainly; abundant fresh collapsed stones may be observed in central Jimingfeng and Taohuafeng; stone drums and stone columns are in the southeastern Shiguliao particularly; enclosed valleys are encircling joints of peaks and plains from three directions east, west, and south. Their spatial combinations reflect that the developments of Danxia landform have undergone stages of geomorphic cyclical erosion in the form of weathering, collapse, transportation, sedimentation and other processes, together with the "sculpture" of external forces mainly as tectonic uplift. The picturesque Danxia landform began its formation at that point. Danxia landform developed mainly in the strata of Fangyan Formation (K1f) caused by the alluvial fan-braided river phase of anterior fan in the late period of the Early Cretaceous. Regular patterns of weathering of stones and features of braided alluvial phase sediments may be verified by the analysis of three groups of experimental data. Danxia landform of Fangyan is a unique representative of the "adolescent" development type in the application of the World Natural Heritages status in China, by virtue of its outstanding universal aesthetic and scientific value.展开更多
Using the digital telemetric seismic waveform data of Chengdu and Kunming, this article studies the focal mechanism solutions and the apparent stress values of a large number of small earthquakes, and then analyzes th...Using the digital telemetric seismic waveform data of Chengdu and Kunming, this article studies the focal mechanism solutions and the apparent stress values of a large number of small earthquakes, and then analyzes the dynamic variation of regional stress fields and the spatio- temporal distribution of apparent stress values. The annual variation values of the azimuth of average principal stress field before the May 12, 2008 Ms8.0 Wenchuan earthquake in the Sichuan-Yunnan region were 58° from 2003 to 2004, 85° from 2003 to 2005,61° from 2006 to 2007 and 90° from 2006 to April 2008 respectively. In recent years, deflection or disturbances occurred in the azimuth of the average principal stress field in the Sichuan-Yunnan region. Analysis shows that this may be related to the change of stress field states of crustal blocks before and after the December 26, 2004 Ms9.0 Sumatra earthquake and the 2008 Ms8.0 Wenchuan earthquake. The ratio of thrust-type earthquakes in the Sichnan-Qinghai block was on the higher side in the period from 2006 to 2007, and the source faulting type of the regional moderate and small earthquakes had changed before the Ms8.0 Wenchnan earthquake. The change of state of the stress field is consistent with the changes in block displacement fields revealed by GPS data and the crustal shortening velocity vertical to the Longmenshan fault zone. Based on the radiation energy calculated from all bands of the seismic waveform, the value of apparent stress σapp is obtained. The fluctuation shape of the fitting trend of the apparent stress is related to the intensity of regional seismicity. It reveals that the micro- dynamic fluctuation process of the regional stress value is similar to the azimuth transition of the regional principal compressive stress field, which can be used to probe for pregnant physical processes. Areas with a higher value of apparent stress σapp are possible areas of potential seismic risk. It can be seen from the spatial distribution of the medium and shortterm apparent stress σapp before the Ms8.0 Wenchuan earthquake, the Longmenshan fault zone is in a low stress distribution area, and the relatively high apparent stress is in the peripheral area. These images may show medium and short-term locking phenomena near the seismogenic tectonics of the Ms8.0 Wenchuan earthquake. For example, changes with time of the focal parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces, continual increase of thrust-type earthquakes in the Sichuan-Qinghai block and the appearance of spatial distribution areas of high apparent σapp stress. The work on this aspect was continued after the Ms8.0 Wenchuan earthquake, and the results seem to be shown a clearer relationship between these phenomena and future great earthquakes.展开更多
Coastal zones comprising important intertidal tropical and subtropical ecosystems are characterized by high productivity, diversity and unique zonation of various plant and animal communities. The comparison of some s...Coastal zones comprising important intertidal tropical and subtropical ecosystems are characterized by high productivity, diversity and unique zonation of various plant and animal communities. The comparison of some selected physicochemical soil properties viz. texture, particle density, moisture content, pH, organic carbon and total nitrogen between planted site (Telir char) and barren site (Boyar char) has been investigated at surface (0-10 cm) and subsurface (10-45 cm) soil across three different land strips viz. inland, middle part and sea side in Lakshmipur coast of Bangladesh. Sand particles in the soil were lower in planted site than barren site. The reverse trend was found in case of both silt and clay percentage. Coastal afforestation had a significant effect on soil binding process since a common trend of increment in soil particle density was noticed. Maximum increment (20.43% to 23.30%) in soil moisture content was recorded in surface soil across the seaside while at subsurface soil both across the middle part (19.53% to 22.30%) and sea side (20.19% to 22.96%). Moreover, the highest reduction in soil pH was recorded at surface soil (7.27 to 6.60) across the sea side and subsurface soil (7.16 to 6.67) in inland due to the influence of coastal plantation. Across all the land strips and the soil depths studied, soil organic carbon was higher in planted site than in barren site with only exception at subsurface soil in the middle part (0.50% in both sites). Total soil nitrogen in the study area was increased at both depths due to forestation with the highest increment in the inland at both surface and subsurface soil.展开更多
Through the sinusoid loading dynamic triaxial test, the liquefaction property of saturated loess and sand selected from a civil airport of Lanzhou, Gansu is examined. Based on the laboratory results, a comprehensive a...Through the sinusoid loading dynamic triaxial test, the liquefaction property of saturated loess and sand selected from a civil airport of Lanzhou, Gansu is examined. Based on the laboratory results, a comprehensive assessment on the earthquake liquefaction potential of the loess and sand is given, using the liquefaction resistance shear stress method and the results of seismic hazard assessment. It is found that under the effect of ground motion with exceedance probability of 10% within 50 years, the loess in the study is more susceptible to liquefaction than sand.展开更多
Mine geology disasters include mine water, mine solid waste, apron and slide, ground collapse sink and underground fracture, etc.. The subject was studied in many ways, and fuzzy mathematics was usually used. It may a...Mine geology disasters include mine water, mine solid waste, apron and slide, ground collapse sink and underground fracture, etc.. The subject was studied in many ways, and fuzzy mathematics was usually used. It may assure the result and distinguish the dangerous rank of different areas. But it has two defects: The first is the result is not very exact, especially the border; The second is it is short of quantity. Fuzzy mathematics and grey theory were used in order to solve the problem. Firstly, mathematical model was constructed by using grey theory, so as to evaluate and forecast the dangerous rank of mining geology disaster in different areas. Then different areas were analyzed and divided by fuzzy mathematics. By doing these, similitude rules are not only studied but also differences are discriminated. Through the practice it can be known that the result is more accurate than before.展开更多
The cultivated land-water resources carrying capacity (CL-WRCC) with the method of system dynamics (SD) were analyzed. Bijie prefecture of Guizhou province served as a case in this study. Bijie prefecture is one o...The cultivated land-water resources carrying capacity (CL-WRCC) with the method of system dynamics (SD) were analyzed. Bijie prefecture of Guizhou province served as a case in this study. Bijie prefecture is one of the least-developed areas in China. In Bijie, the physical and chemical characteristics of karst as well as the rapid economic development lead to the scarcities of cultivated land-water resources (CL-WR). On the basis of analysis on the subsystems of Bijie CL.WRCC system, the fundamental feedback structure of CL-WRCC was presented by causal loop diagram. Considering the three alms (" poverty alleviation and development, ecological construction, and population control") of Bijie as the major goals, Bijie CL-WRCC SD model was developed. Three scenarios, resource-saving and environment-friendly development-oriented scenario (Scenario 1 ), fast economic development-oriented scenario ( Scenario 2 ), and coordinated development-oriented scenario (Scenario 3 ), were investigated. Simulation results indicate that Scenario 3 which takes social economic development, environment protection, and cultivated land- water resources utilization into account, is the best alternative scenario. It can promote the coordination development of society, economy, cultivated land, water resources, and environment. In this study, the technological support and the decision-making for the rational use of CL-WR are provided not only in Bijie, but also in other similar regions of China.展开更多
This paper presents a method of geomorphologic regionalization for Xinjiang, with the use of Srtm-DEM (resolution 90 m) and TM images for 1990 (resolution 30 m). After interpretation and classification of geomorpholog...This paper presents a method of geomorphologic regionalization for Xinjiang, with the use of Srtm-DEM (resolution 90 m) and TM images for 1990 (resolution 30 m). After interpretation and classification of geomorphologic types, the present research focuses on the qualitative and quantitative distribution of different geomorphologic types based on geographical grid analysis. Then, by using system clustering analysis method, geomorphologic types are grouped into divisions. The resulting geomorphologic regionalization hierarchy of Xinjiang includes three levels, i.e., macro-landform divisions, medium-landform divisions, and micro-landform divisions, containing 6, 23 and 200 types, respectively. This method makes it possible to digitally delimit geomorphologic regions. Comparison and verification show that the spatial precision of the boundaries of geomorphologic subareas in Xinjiang is very high.展开更多
The essential principles of the third theory of quantification are discussed, the concept and calculated method of reaction degree are put forward which extend the ap- plying range and scientificalness of the primary ...The essential principles of the third theory of quantification are discussed, the concept and calculated method of reaction degree are put forward which extend the ap- plying range and scientificalness of the primary reaction. Taking the Zhongmacun Mine as example, on the base of analyzing the rules of gas geology synthetically and travers- ing the geological factors infecting coal and gas outburst, the paper adopts the method of combining carving up statistical units with the third theory of quantification, screens out 8 sensitive geological factors from 11 geological indexes and carries through the work of gas geology regionalism to the exploited area of Zhongmacun according to the researching result. The practice shows that it is feasible to apply the third theory of quantification to gas geology, which offers a new thought to screen the sensitive geo- logical factors of gas outburst forecast.展开更多
A central tenet of coevolutionary theory,including theory of the coevolutionary relationship between brood parasites and their hosts,is that temporal and spatial patterns may reveal important information about ecologi...A central tenet of coevolutionary theory,including theory of the coevolutionary relationship between brood parasites and their hosts,is that temporal and spatial patterns may reveal important information about ecological and evolutionary dynamics.For instance,level of genetic structure of populations provides important information about the role of genetics and gene ow in determining local patterns of selection on hosts due to parasitism(i.e.,egg rejection) and on parasites due to selection by hosts(i.e.,egg mimicry).Furthermore,abiotic(i.e.,climatic conditions) and biotic(phenotypic characteristics of animals) factors that also vary spatially may directly or indirectly a ect populations of hosts and brood parasites and,therefore,their interaction.By reviewing the literature,we found considerable evidence for an e ect of the spatially and temporally structured abiotic environment on the phenotype of both parasite and host eggs and the degree of mimicry.Moreover,we found examples suggesting that speci c life history characteristics of hosts that vary geographically and/or temporally may a ect the probability of initial colonization of a new host species and the direction and the speed of coevolution.We provide an exhaustive review of studies investigating temporal and spatial patterns of the interaction between brood parasites and their hosts.Such temporal and spatial trends in parasite and host traits are,together with genetic information on rejection and signi cant e ects of gene ow,consistent with coevolutionary dynamics.However,gene ow and changes in the temporal and spatial patterns of abundance of both parasites and hosts may result in frequent cases of counter-intuitive relationships between the phenotype of the parasite and that of the host(i.e.,poor or no mimicry),which may suggest limits to the degree of adaptation.We provide a list of scienti c questions in need of further investigation,concluding that studies of brood parasites and their hosts may play a central role in testing the geographic theory of coevolution and several alternative hypotheses.展开更多
Dehydration/melting of oceanic crusts during returning to the mantle in subduction zones are related to origin of arc lavas. The factors that influence arc magmatism include compositions of the subducting slabs, mantl...Dehydration/melting of oceanic crusts during returning to the mantle in subduction zones are related to origin of arc lavas. The factors that influence arc magmatism include compositions of the subducting slabs, mantle wedge and subduction rates. However, distinguishing these factors remains difficult and highly debated. Subducting rate is related to the total mass of inputs and controls thermal structure, thus plays a crucial role in arc magmatism. Here we explore the relationships between geochemical variations of arc lavas and convergence rates(increasing from 46 mm/a to the south to 83 mm/a to the northward) in the Tonga-Kermadec arc system. Data of geochemistry for lava samples from nine islands of this arc system are collected and compiled to investigate the role of subduction rate in arc magmatism. Lavas from the northern Tonga arc with a faster subduction rate show broadly lower concentrations of TiO_2 and highfield-strength elements(HFSEs, e.g. Nb, Ta, Zr, Hf), and higher Ba/Th, U/Th ratios than the Kermadec Arc to the south. Some of the Kermadec lavas show the highest values of Th/Nb ratio. We suggest that the northern Tonga arc with a higher subduction rate has been influenced by a stronger role of subductionreleased fluid, which results in stronger large-ion-lithophile elements(LILEs) and relatively weaker HFSEs contribution. It is interpreted that faster subduction rate tend to create a cooler subduction zone, leading to stronger dehydration subduction slab contribution with, thus, higher LILE/HFSE ratios of arc lavas. The conclusion contributes to a better understanding of arc magmatism, and ultimately the long-term chemical differentiation of the Earth. More supplementary geochemical data along Tonga-Kermadec arc and tests in other arcs are needed.展开更多
Based on the coupfing between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found th...Based on the coupfing between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found that the motion of a spinning particle deviates from the geodesic trajectory, and this deviation originates from the coupling between the spin of the particle and gravitoelectromagnetic field, which is also the origin of Lense-Thirring effects. In post-Newtonian approximations, this equation gives the same results as those of Mathisson-Papapetrou equation. Effect of the deviation of geodesic trajectory is detectable.展开更多
A new numerical model is presented to simulate fracture initiation and propagation in geological structures. This model is based on the recent amalgamation of established failure and fracture mechanics theory, which h...A new numerical model is presented to simulate fracture initiation and propagation in geological structures. This model is based on the recent amalgamation of established failure and fracture mechanics theory, which has been implemented to the finite difference FLAC code as a constitutive FISH userdefined-model. Validation of the model has been studied on the basis of comparing the transitional failure modes in rock. It is shown that the model is capable of accurately simulating fracture distributions over entire brittle to ductile rock phases. The application of the model during longwall retreat simulation highlighted several caving characteristics relevant to varying geological condition. The distribution and behaviour of modelled fractures were both realistic and shown to provide an enhanced post failure analysis to geological structures in FLAC. Moreover, the model introduces new potential insight towards the failure analysis of more complicated problems. This is best suited towards improving safety and efficiency in mines through the prediction of various key fractures and caving characteristics of geological structures.展开更多
This thesis illustrates the method and precision of employing analytical photogrammetry to carry out similar materials model experiment in surveying the displacement of surveying points and analyzing the deformation l...This thesis illustrates the method and precision of employing analytical photogrammetry to carry out similar materials model experiment in surveying the displacement of surveying points and analyzing the deformation law of rock layersand earths surface according to the results in the studying the deformation law of the earths surface caused by extracting mine coal underground.展开更多
Crustal stress field holds an important position in geodynamics research, such as in plate motion simulations, uplift of the Qinghai-Xizang (Tibet) Plateau and earthquake preparation and occurrence. However, most of t...Crustal stress field holds an important position in geodynamics research, such as in plate motion simulations, uplift of the Qinghai-Xizang (Tibet) Plateau and earthquake preparation and occurrence. However, most of the crustal stress studies emphasize particularly on the determination of stress direction, with little study being done on stress magnitude at present. After reviewing ideas on a stress magnitude study from geological, geophysical and various other aspects, a method to estimate the stress magnitude in the source region according to the deflection of stress direction before and after large earthquakes and the stress drop tensor of earthquake rupture has been developed. The proposed method can also be supplemented by the average apparent stress before and after large earthquakes. The stress direction deflection before and after large earthquakes can be inverted by massive focal mechanisms of foreshocks and aftershocks and the stress drop field generated by the seismic source can be calculated by the detailed distribution of the earthquakes rupture. The mathematical relationship can then be constructed between the stress drop field, where its magnitude and direction are known and the stress tensor before and after large earthquakes, where its direction is known but magnitude is unknown, thereby obtaining the stress magnitude. The average apparent stress before and after large earthquakes can be obtained by using the catalog of broadband radiated energy and seismic moment tensor of foreshocks and aftershocks and the different responses to stress drops. This relationship leads to another estimation of stress magnitude before a large earthquake. The stress magnitude and its error are constrained by combining the two methods, which provide new constraints for the geodynamics study.展开更多
Earthquake prediction is a difficult problem in Earth sciences.Unsuccessful predictions one after another urged people to explore more synthetic and comprehensive methods for earthquake prediction.The Lithosphere-Atmo...Earthquake prediction is a difficult problem in Earth sciences.Unsuccessful predictions one after another urged people to explore more synthetic and comprehensive methods for earthquake prediction.The Lithosphere-Atmosphere-Ionosphere(LAI)coupling theory pays great attention to the processes taking place within the near ground layer of atmosphere.It has achieved great results recently,and can enlighten us about the nature of an earthquake's precursor.Based on the NCEP reanalysis dataset,this paper attempts to track the anomalies of the surface's upward long wave radiation flux(ULWRF),the temperature at the depth of 10cm~20cm below ground surface layer(BGL)and the air temperature at 2 meters above ground surface(AIR)around the time of the strong Wenchuan earthquake.Thermal anomalies were observed before and after May 12,2008,the time of the Wenchuan earthquake.Perhaps the thermal anomaly that occurred prior to the earthquake can be taken as indicators of the earthquake,but in view of the complexity of the earthquake phenomena,using thermal anomaly as a precursor should be done with caution.展开更多
Recently the Journal of Mountain Science published three papers(Lumbres et al.2014;Jung et al.2015;Lumbres et al.2016)that compared selected taper models for bias and precision when estimating upper stem diameters f...Recently the Journal of Mountain Science published three papers(Lumbres et al.2014;Jung et al.2015;Lumbres et al.2016)that compared selected taper models for bias and precision when estimating upper stem diameters for various tree species.展开更多
Based on ArcGIS and MapInfo software, we digitized the active tectonics map (1:4,000,000) of China, which was compiled and revised by academician Deng Qidong, and built the spatial database of active tectonics of Chin...Based on ArcGIS and MapInfo software, we digitized the active tectonics map (1:4,000,000) of China, which was compiled and revised by academician Deng Qidong, and built the spatial database of active tectonics of China. The database integrates rich active tectonic data, such as a catalogue of earthquakes with magnitude above 6.0, active faults, Quaternary basins, active folds and their associated attribute parameters, and implements scientific and effective management to this data. At the same time, the spatial database joins the spatial map data and the associated attribute data together, which implements the data query between spatial properties and attribute parameters and also makes it possible to perform spatial analysis with different data layers. These provide much convenience for earthquake study and allows engineering construction institutions to use this data in practical applications.展开更多
文摘Through reviewing the flow theory’s birth and development history in underground porous media and contrasting the mechanics of underground fluids and mechanics of viscous fluids, this paper points out the main factors, which affect the development of the theory on oil and gas porous flow. The development law and development route of the mechanics of fluids in porous media are also summarized in this paper.
基金National Natural Science Foundation of China, No.40701017
文摘Present granite landform characteristics and distribution are the integrated result of climate, tectonics and lithology. Various types of granite landforms in China signify climate zonality and differential vertical movement of earth surface, while published research results on Chinese granite landforms are very rare, especially in international journals. Based on the process analysis of chemical weathering and physical disintegration, four granite landform regions in China are classified according to the present climate regime. On the Tibetan Plateau, the cold and freezing climate induced periglacial landscapes; the northeast region is characterized by physical disintegration and low round mounds are widespread; in the northwest region controlled by arid climate, wind-carved minor landscapes are extremely prominent. The most spectacular granite landscapes in China are presented in southeast as a result of Iongtime chemical weathering under humid and warm conditions, as well as the differential uplift after Neogene. Correlating the weathering crust in southern China, Tibetan Plateau and India, a possible unified planation surface in Neogene is proposed. With corestones as indicators of original weathering front, the differential uplift extent of dissected planation surfaces can be estimated. At least three landforms implying uplift can be identified in southeastern China, with elevations of 300-400 m, 2000 m and 3600 m above the sea level respectively.
基金National Natural Science Foundation of China, No.40871014The Open Foundation of the State Key Labo-ratory of Loess and Quaternary Geology from the Institute of Earth Environment, CAS, No.SKLLQG0817+1 种基金The Training Foundation of National Basis of Talents, No.J0630535Project of Application World Natural Heritages of Construction Bureau of Zhejiang Province, The Test Foundation of Modern Analyses Center of Nanjing University
文摘The prominent types of Danxia landform in Fangyan include enclosed valleys, mesas, peaks, stone columns and grooves etc. Their spatial combinations have regular configurations along the northwest–southeast direction: typical grooves and caves are located in the northwestern Wufengshuyuan mainly; abundant fresh collapsed stones may be observed in central Jimingfeng and Taohuafeng; stone drums and stone columns are in the southeastern Shiguliao particularly; enclosed valleys are encircling joints of peaks and plains from three directions east, west, and south. Their spatial combinations reflect that the developments of Danxia landform have undergone stages of geomorphic cyclical erosion in the form of weathering, collapse, transportation, sedimentation and other processes, together with the "sculpture" of external forces mainly as tectonic uplift. The picturesque Danxia landform began its formation at that point. Danxia landform developed mainly in the strata of Fangyan Formation (K1f) caused by the alluvial fan-braided river phase of anterior fan in the late period of the Early Cretaceous. Regular patterns of weathering of stones and features of braided alluvial phase sediments may be verified by the analysis of three groups of experimental data. Danxia landform of Fangyan is a unique representative of the "adolescent" development type in the application of the World Natural Heritages status in China, by virtue of its outstanding universal aesthetic and scientific value.
基金Scientific and Technology project(200808053)National Key Basic Research 973b project support
文摘Using the digital telemetric seismic waveform data of Chengdu and Kunming, this article studies the focal mechanism solutions and the apparent stress values of a large number of small earthquakes, and then analyzes the dynamic variation of regional stress fields and the spatio- temporal distribution of apparent stress values. The annual variation values of the azimuth of average principal stress field before the May 12, 2008 Ms8.0 Wenchuan earthquake in the Sichuan-Yunnan region were 58° from 2003 to 2004, 85° from 2003 to 2005,61° from 2006 to 2007 and 90° from 2006 to April 2008 respectively. In recent years, deflection or disturbances occurred in the azimuth of the average principal stress field in the Sichuan-Yunnan region. Analysis shows that this may be related to the change of stress field states of crustal blocks before and after the December 26, 2004 Ms9.0 Sumatra earthquake and the 2008 Ms8.0 Wenchuan earthquake. The ratio of thrust-type earthquakes in the Sichnan-Qinghai block was on the higher side in the period from 2006 to 2007, and the source faulting type of the regional moderate and small earthquakes had changed before the Ms8.0 Wenchnan earthquake. The change of state of the stress field is consistent with the changes in block displacement fields revealed by GPS data and the crustal shortening velocity vertical to the Longmenshan fault zone. Based on the radiation energy calculated from all bands of the seismic waveform, the value of apparent stress σapp is obtained. The fluctuation shape of the fitting trend of the apparent stress is related to the intensity of regional seismicity. It reveals that the micro- dynamic fluctuation process of the regional stress value is similar to the azimuth transition of the regional principal compressive stress field, which can be used to probe for pregnant physical processes. Areas with a higher value of apparent stress σapp are possible areas of potential seismic risk. It can be seen from the spatial distribution of the medium and shortterm apparent stress σapp before the Ms8.0 Wenchuan earthquake, the Longmenshan fault zone is in a low stress distribution area, and the relatively high apparent stress is in the peripheral area. These images may show medium and short-term locking phenomena near the seismogenic tectonics of the Ms8.0 Wenchuan earthquake. For example, changes with time of the focal parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces, continual increase of thrust-type earthquakes in the Sichuan-Qinghai block and the appearance of spatial distribution areas of high apparent σapp stress. The work on this aspect was continued after the Ms8.0 Wenchuan earthquake, and the results seem to be shown a clearer relationship between these phenomena and future great earthquakes.
文摘Coastal zones comprising important intertidal tropical and subtropical ecosystems are characterized by high productivity, diversity and unique zonation of various plant and animal communities. The comparison of some selected physicochemical soil properties viz. texture, particle density, moisture content, pH, organic carbon and total nitrogen between planted site (Telir char) and barren site (Boyar char) has been investigated at surface (0-10 cm) and subsurface (10-45 cm) soil across three different land strips viz. inland, middle part and sea side in Lakshmipur coast of Bangladesh. Sand particles in the soil were lower in planted site than barren site. The reverse trend was found in case of both silt and clay percentage. Coastal afforestation had a significant effect on soil binding process since a common trend of increment in soil particle density was noticed. Maximum increment (20.43% to 23.30%) in soil moisture content was recorded in surface soil across the seaside while at subsurface soil both across the middle part (19.53% to 22.30%) and sea side (20.19% to 22.96%). Moreover, the highest reduction in soil pH was recorded at surface soil (7.27 to 6.60) across the sea side and subsurface soil (7.16 to 6.67) in inland due to the influence of coastal plantation. Across all the land strips and the soil depths studied, soil organic carbon was higher in planted site than in barren site with only exception at subsurface soil in the middle part (0.50% in both sites). Total soil nitrogen in the study area was increased at both depths due to forestation with the highest increment in the inland at both surface and subsurface soil.
基金founded by the Special Social Commonweal Research Programs of the Ministry of Science and Technology of China (Grant No.2004DIB3J130)
文摘Through the sinusoid loading dynamic triaxial test, the liquefaction property of saturated loess and sand selected from a civil airport of Lanzhou, Gansu is examined. Based on the laboratory results, a comprehensive assessment on the earthquake liquefaction potential of the loess and sand is given, using the liquefaction resistance shear stress method and the results of seismic hazard assessment. It is found that under the effect of ground motion with exceedance probability of 10% within 50 years, the loess in the study is more susceptible to liquefaction than sand.
文摘Mine geology disasters include mine water, mine solid waste, apron and slide, ground collapse sink and underground fracture, etc.. The subject was studied in many ways, and fuzzy mathematics was usually used. It may assure the result and distinguish the dangerous rank of different areas. But it has two defects: The first is the result is not very exact, especially the border; The second is it is short of quantity. Fuzzy mathematics and grey theory were used in order to solve the problem. Firstly, mathematical model was constructed by using grey theory, so as to evaluate and forecast the dangerous rank of mining geology disaster in different areas. Then different areas were analyzed and divided by fuzzy mathematics. By doing these, similitude rules are not only studied but also differences are discriminated. Through the practice it can be known that the result is more accurate than before.
基金Knowledge Innovation Project of Chinese Academy of Sciences(CAS),China(No.KZCX2-YW-333)
文摘The cultivated land-water resources carrying capacity (CL-WRCC) with the method of system dynamics (SD) were analyzed. Bijie prefecture of Guizhou province served as a case in this study. Bijie prefecture is one of the least-developed areas in China. In Bijie, the physical and chemical characteristics of karst as well as the rapid economic development lead to the scarcities of cultivated land-water resources (CL-WR). On the basis of analysis on the subsystems of Bijie CL.WRCC system, the fundamental feedback structure of CL-WRCC was presented by causal loop diagram. Considering the three alms (" poverty alleviation and development, ecological construction, and population control") of Bijie as the major goals, Bijie CL-WRCC SD model was developed. Three scenarios, resource-saving and environment-friendly development-oriented scenario (Scenario 1 ), fast economic development-oriented scenario ( Scenario 2 ), and coordinated development-oriented scenario (Scenario 3 ), were investigated. Simulation results indicate that Scenario 3 which takes social economic development, environment protection, and cultivated land- water resources utilization into account, is the best alternative scenario. It can promote the coordination development of society, economy, cultivated land, water resources, and environment. In this study, the technological support and the decision-making for the rational use of CL-WR are provided not only in Bijie, but also in other similar regions of China.
基金Consulting projects of CAS Academicians, No.KZCX3-SW-347National Natural Science Foundation of China, No.40871177+1 种基金Project of State Key Lab of Resources and Environmental Information System, No.O88RA304SACAS Knowledge Innovation Project
文摘This paper presents a method of geomorphologic regionalization for Xinjiang, with the use of Srtm-DEM (resolution 90 m) and TM images for 1990 (resolution 30 m). After interpretation and classification of geomorphologic types, the present research focuses on the qualitative and quantitative distribution of different geomorphologic types based on geographical grid analysis. Then, by using system clustering analysis method, geomorphologic types are grouped into divisions. The resulting geomorphologic regionalization hierarchy of Xinjiang includes three levels, i.e., macro-landform divisions, medium-landform divisions, and micro-landform divisions, containing 6, 23 and 200 types, respectively. This method makes it possible to digitally delimit geomorphologic regions. Comparison and verification show that the spatial precision of the boundaries of geomorphologic subareas in Xinjiang is very high.
基金Supported by"973"Key Foundation of China (2002CB211704).
文摘The essential principles of the third theory of quantification are discussed, the concept and calculated method of reaction degree are put forward which extend the ap- plying range and scientificalness of the primary reaction. Taking the Zhongmacun Mine as example, on the base of analyzing the rules of gas geology synthetically and travers- ing the geological factors infecting coal and gas outburst, the paper adopts the method of combining carving up statistical units with the third theory of quantification, screens out 8 sensitive geological factors from 11 geological indexes and carries through the work of gas geology regionalism to the exploited area of Zhongmacun according to the researching result. The practice shows that it is feasible to apply the third theory of quantification to gas geology, which offers a new thought to screen the sensitive geo- logical factors of gas outburst forecast.
文摘A central tenet of coevolutionary theory,including theory of the coevolutionary relationship between brood parasites and their hosts,is that temporal and spatial patterns may reveal important information about ecological and evolutionary dynamics.For instance,level of genetic structure of populations provides important information about the role of genetics and gene ow in determining local patterns of selection on hosts due to parasitism(i.e.,egg rejection) and on parasites due to selection by hosts(i.e.,egg mimicry).Furthermore,abiotic(i.e.,climatic conditions) and biotic(phenotypic characteristics of animals) factors that also vary spatially may directly or indirectly a ect populations of hosts and brood parasites and,therefore,their interaction.By reviewing the literature,we found considerable evidence for an e ect of the spatially and temporally structured abiotic environment on the phenotype of both parasite and host eggs and the degree of mimicry.Moreover,we found examples suggesting that speci c life history characteristics of hosts that vary geographically and/or temporally may a ect the probability of initial colonization of a new host species and the direction and the speed of coevolution.We provide an exhaustive review of studies investigating temporal and spatial patterns of the interaction between brood parasites and their hosts.Such temporal and spatial trends in parasite and host traits are,together with genetic information on rejection and signi cant e ects of gene ow,consistent with coevolutionary dynamics.However,gene ow and changes in the temporal and spatial patterns of abundance of both parasites and hosts may result in frequent cases of counter-intuitive relationships between the phenotype of the parasite and that of the host(i.e.,poor or no mimicry),which may suggest limits to the degree of adaptation.We provide a list of scienti c questions in need of further investigation,concluding that studies of brood parasites and their hosts may play a central role in testing the geographic theory of coevolution and several alternative hypotheses.
基金Supported by the National Natural Science Foundation of China(Nos.41376065,41522602)the National Program on Global Change and AirSea Interaction(No.GASI-GEOGE-02)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA11030103)the Project of“Ao Shan”Excellent Scholar for Qingdao National Laboratory for Marine Science and Technology
文摘Dehydration/melting of oceanic crusts during returning to the mantle in subduction zones are related to origin of arc lavas. The factors that influence arc magmatism include compositions of the subducting slabs, mantle wedge and subduction rates. However, distinguishing these factors remains difficult and highly debated. Subducting rate is related to the total mass of inputs and controls thermal structure, thus plays a crucial role in arc magmatism. Here we explore the relationships between geochemical variations of arc lavas and convergence rates(increasing from 46 mm/a to the south to 83 mm/a to the northward) in the Tonga-Kermadec arc system. Data of geochemistry for lava samples from nine islands of this arc system are collected and compiled to investigate the role of subduction rate in arc magmatism. Lavas from the northern Tonga arc with a faster subduction rate show broadly lower concentrations of TiO_2 and highfield-strength elements(HFSEs, e.g. Nb, Ta, Zr, Hf), and higher Ba/Th, U/Th ratios than the Kermadec Arc to the south. Some of the Kermadec lavas show the highest values of Th/Nb ratio. We suggest that the northern Tonga arc with a higher subduction rate has been influenced by a stronger role of subductionreleased fluid, which results in stronger large-ion-lithophile elements(LILEs) and relatively weaker HFSEs contribution. It is interpreted that faster subduction rate tend to create a cooler subduction zone, leading to stronger dehydration subduction slab contribution with, thus, higher LILE/HFSE ratios of arc lavas. The conclusion contributes to a better understanding of arc magmatism, and ultimately the long-term chemical differentiation of the Earth. More supplementary geochemical data along Tonga-Kermadec arc and tests in other arcs are needed.
文摘Based on the coupfing between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found that the motion of a spinning particle deviates from the geodesic trajectory, and this deviation originates from the coupling between the spin of the particle and gravitoelectromagnetic field, which is also the origin of Lense-Thirring effects. In post-Newtonian approximations, this equation gives the same results as those of Mathisson-Papapetrou equation. Effect of the deviation of geodesic trajectory is detectable.
文摘A new numerical model is presented to simulate fracture initiation and propagation in geological structures. This model is based on the recent amalgamation of established failure and fracture mechanics theory, which has been implemented to the finite difference FLAC code as a constitutive FISH userdefined-model. Validation of the model has been studied on the basis of comparing the transitional failure modes in rock. It is shown that the model is capable of accurately simulating fracture distributions over entire brittle to ductile rock phases. The application of the model during longwall retreat simulation highlighted several caving characteristics relevant to varying geological condition. The distribution and behaviour of modelled fractures were both realistic and shown to provide an enhanced post failure analysis to geological structures in FLAC. Moreover, the model introduces new potential insight towards the failure analysis of more complicated problems. This is best suited towards improving safety and efficiency in mines through the prediction of various key fractures and caving characteristics of geological structures.
文摘This thesis illustrates the method and precision of employing analytical photogrammetry to carry out similar materials model experiment in surveying the displacement of surveying points and analyzing the deformation law of rock layersand earths surface according to the results in the studying the deformation law of the earths surface caused by extracting mine coal underground.
基金sponsored by the National Science Foundation Program(40374012)the Joint Earthquake Science Foundation Program(A07015),China
文摘Crustal stress field holds an important position in geodynamics research, such as in plate motion simulations, uplift of the Qinghai-Xizang (Tibet) Plateau and earthquake preparation and occurrence. However, most of the crustal stress studies emphasize particularly on the determination of stress direction, with little study being done on stress magnitude at present. After reviewing ideas on a stress magnitude study from geological, geophysical and various other aspects, a method to estimate the stress magnitude in the source region according to the deflection of stress direction before and after large earthquakes and the stress drop tensor of earthquake rupture has been developed. The proposed method can also be supplemented by the average apparent stress before and after large earthquakes. The stress direction deflection before and after large earthquakes can be inverted by massive focal mechanisms of foreshocks and aftershocks and the stress drop field generated by the seismic source can be calculated by the detailed distribution of the earthquakes rupture. The mathematical relationship can then be constructed between the stress drop field, where its magnitude and direction are known and the stress tensor before and after large earthquakes, where its direction is known but magnitude is unknown, thereby obtaining the stress magnitude. The average apparent stress before and after large earthquakes can be obtained by using the catalog of broadband radiated energy and seismic moment tensor of foreshocks and aftershocks and the different responses to stress drops. This relationship leads to another estimation of stress magnitude before a large earthquake. The stress magnitude and its error are constrained by combining the two methods, which provide new constraints for the geodynamics study.
文摘Earthquake prediction is a difficult problem in Earth sciences.Unsuccessful predictions one after another urged people to explore more synthetic and comprehensive methods for earthquake prediction.The Lithosphere-Atmosphere-Ionosphere(LAI)coupling theory pays great attention to the processes taking place within the near ground layer of atmosphere.It has achieved great results recently,and can enlighten us about the nature of an earthquake's precursor.Based on the NCEP reanalysis dataset,this paper attempts to track the anomalies of the surface's upward long wave radiation flux(ULWRF),the temperature at the depth of 10cm~20cm below ground surface layer(BGL)and the air temperature at 2 meters above ground surface(AIR)around the time of the strong Wenchuan earthquake.Thermal anomalies were observed before and after May 12,2008,the time of the Wenchuan earthquake.Perhaps the thermal anomaly that occurred prior to the earthquake can be taken as indicators of the earthquake,but in view of the complexity of the earthquake phenomena,using thermal anomaly as a precursor should be done with caution.
文摘Recently the Journal of Mountain Science published three papers(Lumbres et al.2014;Jung et al.2015;Lumbres et al.2016)that compared selected taper models for bias and precision when estimating upper stem diameters for various tree species.
文摘Based on ArcGIS and MapInfo software, we digitized the active tectonics map (1:4,000,000) of China, which was compiled and revised by academician Deng Qidong, and built the spatial database of active tectonics of China. The database integrates rich active tectonic data, such as a catalogue of earthquakes with magnitude above 6.0, active faults, Quaternary basins, active folds and their associated attribute parameters, and implements scientific and effective management to this data. At the same time, the spatial database joins the spatial map data and the associated attribute data together, which implements the data query between spatial properties and attribute parameters and also makes it possible to perform spatial analysis with different data layers. These provide much convenience for earthquake study and allows engineering construction institutions to use this data in practical applications.