太湖风生流数值模式及其对总磷分布的影响

A new up-winding finite element numerical model, which is two-dimensional and suitable for modeling lake current and the distribution of total phosphorus(TP) in shallow lakes, is derived. Moreover, it is used in the study of wind-driven current in Taihu Lake, and the impact of lake current field on the distribution of TP is also discussed.     

SHRIMP zircon U-Pb age and Nd isotopic study on the Nyainqêntanglha Group in Tibet

The Nyainqêntanglha Group, called Nyainqêntan- glha orthogneisses and schist sequence by Li et al.[1], is traditionally viewed as the oldest metamorphic basement in the Lhasa block[1―4]. The uplifted blocks of basement have exposed in two regions, middle segment of Nyainqêntanglha Mountain Range and west of Nam Co. The Nyainqêntanglha Group is sparsely dated, for its protolith age, the previous ideas were very different, such as Proterozoic, Pre-Sinian, Precambrian, or early Paleozo…     

Discussion on the Relation Between the Probabilistic Distribution of Magnitude in a Seismic Province and That in an Area with Potential Seismic Source

According to the joint probabilistic distribution model of magnitude and space,the author discusses the relationship between the probabilistic distribution of magnitude in a seismic province and that in an area with potential seismic sources.The results show that if the magnitude probabilistic distribution follows the truncated exponential form in a seismic province,there must be some potential source in which the magnitude probabilistic distribution does not conform to that form.The result is consistent with the concept of "characteristic earthquake" derived from the study of actual records of seismicity and the study of geology.The author suggests that the relationship between the probabilistic distribution of magnitude in a seismic province and that in a seismic potential area must be considered in the study of the analysis of seismicity,seismic zonation and engineering seismology,for the purpose of the evaluation of the probabilistic distribution of magnitude correctly in every area with potential s     

Texture and tectonic attribute of Cenozoic basin basement in the northern South China Sea

Based on the drilling data,the geological characteristics of the coast in South China,and the interpretation of the long seismic profiles covering the Pearl River Mouth Basin and southeastern Hainan Basin,the basin basement in the northern South China Sea is divided into four structural layers,namely,Pre-Sinian crystalline basement,Sinian-lower Paleozoic,upper Paleozoic,and Mesozoic structural layers.This paper discusses the distribution range and law and reveals the tectonic attribute of each structural layer.The Pre-Sinian crystalline basement is distributed in the northern South China Sea,which is linked to the Pre-Sinian crystalline basement of the Cathaysian Block and together they constitute a larger-scale continental block—the Cathaysian-northern South China Sea continental block.The Sinian-lower Paleozoic structural layer is distributed in the northern South China Sea,which is the natural extension of the Caledonian fold belt in South China to the sea area.The sediments are derived from southern East China Sea-Taiwan,Zhongsha-Xisha islands and Yunkai ancient uplifts,and some small basement uplifts.The Caledonian fold belt in the northern South China Sea is linked with that in South China and they constitute the wider fold belt.The upper Paleozoic structural layer is unevenly distributed in the northern South China.In the basement of Beibu Gulf Basin and southwestern Taiwan Basin,the structural layer is composed of the stable epicontinental sea deposit.The distribution areas in the Pearl River Mouth Basin and the southeastern Hainan Basin belong to ancient uplifts in the late Paleozoic,lacking the upper Paleozoic structural layers.The stratigraphic distribution and sedimentary environment in Middle-Late Jurassic to Cretaceous are characteristic of differentiation in the east and the west.The marine,paralic deposit is well developed in the basin basement of southwestern Taiwan but the volcanic activity is not obvious.The marine and paralic facies deposit is distributed in the eastern Pearl River Mouth Basin basement and the volcanic activity is stronger.The continental facies volcano-sediment in the Early Cretaceous is distributed in the basement of the western Pearl River Mouth Basin and Southeastern Hainan Basin.The Upper Cretaceous red continental facies clastic rocks are distributed in the Beibu Gulf Basin and Yinggehai Basin.The NE direction granitic volcanic-intrusive complex,volcano-sedimentary basin,fold and fault in Mesozoic basement have the similar temporal and spatial distribution,geological feature,and tectonic attribute with the coastal land in South China,and they belong to the same magma-deposition-tectonic system,which demonstrates that the late Mesozoic structural layer was formed in the background of active continental margin.Based on the analysis of basement structure and the study on tectonic attribute,the paleogeographic map of the basin basement in different periods in the northern South China Sea is compiled.     

Crustal structure using receiver function in the east part of A’nyêmaqên suture belt

Twenty broadband seismographs were deployed along Hongyuan, Sichuan to Wuwei, Gansu. 81 teleseismic events were recorded in one year. We computed receiver functions from teleseismic waveform data and obtained S wave velocity structure beneath each station along the profile by using receiver function inversion method. The results revealed that the crustal structure is very complex and crustal average S wave velocity is to be on the low side. Low velocity structure generally exists in the depth range of 10~40 km in the crust between Aba arc fault and northern edge fault of Qinling earth’s axis and it is a tectonic feature of complex geological process such as ancient A’nyêmaqên Tethys ocean from closing and side colliding to subducted plate exhumed or thrust rock slice lifted. The Moho is about 50 km depth along the profile and is slightly deeper in the south than in the north.     

Magnitude and distance distribution of strong aftershocks in Sichuan-Yunnan region

Using the earthquake sequences data with MS≥6.5 since 1966 in Sichuan-Yunnan region, we research the charac-teristic of the magnitude difference distribution between main shocks and their strong aftershocks; and then study the spatial distribution characteristic of the strong aftershocks away from their main shocks. The result shows that the magnitude difference distribution obeys intercepted exponential distribution, while the spatial distribution of strong aftershocks obeys normal distribution and the dominated distribution area of strong shocks is 10~39 km away from main shock. Finally the probability density function of the magnitude difference distribution and the spatial distribution of strong aftershocks is deduced.     

Fault plane parameters of Tancheng M81/2 earthquake on the basis of present-day seismological data

The great Tancheng earthquake of M81/2 occurred in 1668 was the largest seismic event ever recorded in history in eastern China.This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area.We relocated those earthquakes with the double-difference method and found focal mechanism solutions using gird test method.The inversion results are as follows:the strike is 21.6°,the dip angle is 89.5°,the slip angle is 170°,the fault length is about 160 km,the lower-boundary depth is about 32 km and the buried depth of upper boundary is about 4 km.This shows that the seismic fault is a NNE-trending upright right-lateral strike-slip fault and has cut through the crust.Moreover,the surface seismic fault,intensity distribution of the earthquake,earthquake-depth distribution and seismic-wave velocity profile in the focal area all verified our study result.     

Sketch of Epicentral Distribution of Positive and Negative Earthquake and Its Application to the Response Ratio Theory

INTRODUCTION It is common knowledge that the development and occurrence of an earthquake is a very complicated geophysical process. An earthquake is caused by the local failure of the earth crust medium, and earthquakes are distributed inhomogeneously in space. Seismic activities, however, are a real reflection of the interaction of the faults, which provides us some information concerning the earth crust medium and may help us predict the earthquake. Therefore, the study of the seismicity pattern can become a means of earthquake prediction. In order to reflect directly the spacial distribution of seismic activities, the sketch of epicentral distribution has been widety used in the study     

Tomography for Q of the Eastern Section of the Tianshan Area from High-frequency Attenuation of S-wave

Based on the waveform data of 5,076 local earthquakes recorded at 25 stations in Xinjiang during the period from 2009 to 2014 and the observation reports provided by the Xinjiang Digital Seismic Network,a data set of 19,140 attenuation factors t*is obtained by fitting the high-frequency attenuation of S-wave spectra with a genetic algorithm. The spatial distribution of Q_S is determined by inverting the t*data with seismic tomography. The results show that the average Q0 in eastern Tianshan is 520,and there is a significant correlation between the Q_S value distribution or attenuation characteristics it disclosed and the surface structure of the study area. The Q_S value is lower in the intersection area of the mountain basin which is located on the north and south sides of the Tianshan Mountains,and the high Q_S distribution is more concentrated inside the Tianshan orogenic belt. The M≥6. 0 earthquakes have been basically located in the Low-Q_S region since 1900. 24 high heat flow points in eastern Tianshan are located at the north and south of Tianshan Mountains where low Q_S exists,indicating a negative correlation. In addition,there is a positive correlation between the velocity structure and the attenuation structure in the study area,which reflects the consistency of the 2-D attenuation structure with the velocity structure and the two-dimensional density structure.     

NUMERICAL STUDY ON ENVIRONMENTAL IMPACTS OF THE THIRD SHANGHAI SEWERAGE PROJECT

1 INTRODUCTION Shanghai, Chinas largest metropolitan area with a population of about 14 million, is situated at the mouth of the Yangtze River, and bordered with the East China Sea to the east, Hangzhou Bay to the south, and the provinces of Zhejiang and Jiangsu to the west. It is a region with intensive distribution of rivers and lakes. The good geographic location and natural conditions have provided the city with superiority in its social and economic center and port city of the co…     

Distribution,health and ecological risk assessments of trace elements in Nigerian oil sands

The Nigerian oil sands represent the largest oil sand deposit in Africa, yet there is little published information on the distribution and potential health and ecological risks of trace elements in the oil resource. In the present study, we investigated the distribution pattern of 18trace elements(including biophile and chalcophile elements) as well as the estimated risks associated with exposure to these elements. The results of the study indicated that Fe was the most abundant element, with a ...     

Ecological risk assessment of surficial sediment by heavy metals from a submerged archaeology harbor,South Mediterranean Sea,Egypt

A protected semi-enclosed embayment,the Eastern Harbor(EH),is situated in the central sector of the Mediterranean coast of Alexandria,Egypt.It is a famous fishing dock and water-sport center and its importance arose after the discovery of the Ptolemaic royal quarter of ancient Alexandria.To protect this national treasure and improve its environmental health,the untreated anthropogenic effluents,which continued for decades into the EH since 1992,must be totally stopped.Accordingly,it is an important issue to continually monitor and asses the environmental status of the EH.The sediment texture,total organic carbon,and the accumulation,distribution,and ecological risks of Cd,Cr,Pb,As,Hg and A1 were determined with a total of 14 surficial sediments samples collected in the EH during 2010.Metal contents were compared to the literature data to assess the pollution status of sediments.Enrichment factors,Degree of contamination(mCd)and potential ecological risk were calculated as a criterion of possible contamination.Since mCd calculation produces an overall average value for a range of pollutants,in the present study the contamination factor that provides a measure of the degree of overall contamination in the surface layers in a particular sampling site may provide a better indication of the state of pollution in the EH sediments than other indicators.     

Empirical approaches in prediction of reservoir sediment distribution——An experience of 57 reservoirs in the USA and India

An accurate prediction of sediment distribution may minimize economic losses through proper and timely planning of the functional activities of a reservoir.This study assesses different temporal and spatial factors that affect for sediment deposition in a reservoir and its distribution.This study also focuses on evaluation of two popular distribution prediction methodologies,Area Increment and Empirical Area Reduction,based on experience with sediment distribution in 57 reservoirs in the USA and India.A non-iterative processed empirical distribution model(NPEDM) and a linear regression trend model(LRTM) are proposed to predict sediment distribution.Silt contributing area and inflow entering a reservoir are found to be the most significant factors affecting in reservoir sediment deposition.Compared to the Empirical Area Reduction method,the Area Increment method provided better prediction.The reservoir classification approach and empirical design distribution type curves given by Borland and Miller(1960) are found to be rational.Shape factor values for different periods indicate that reservoir shape(type) changes with time.Thus,long term prediction is not desirable in Type-Ⅱ Ⅲ reservoirs using the Empirical Area Reduction method.Newly developed the NPEDM shows reasonably good prediction of sediment distribution.The NPEDM is very easy to apply and can be used in any reservoir of any size.Extrapolation of the trend of sediment distribution obtained from the LRTM indicates an accurate short term prediction in a few reservoirs as causes of temporal and spatial variations of sediment distribution including the factors of uncertainties of sediment deposition are implicit within the methodology.     

Grain-size distribution in suspension over a sand-gravel bed in open channel flow

Grain-size distributions of suspended load over a sand-gravel bed at two different flow velocities were studied in a laboratory flume.The experiments had been performed to study the influence of flow velocity and suspension height on grain-size distribution in suspension over a sand-gravel bed.The experimental findings show that with an increase of flow velocity,the grain-size distribution of suspended load changed from a skewed form to a bimodal one at higher suspension heights.This study focuses on the determination of the parameter β_n which is the ratio of the sediment diffusion coefficient to the momentum diffusion coefficient of n th grain-size.A new relationship has been proposed involving β_n,the normalizing settling velocity of sediment particles and suspension height,which is applicable for widest range of normalizing settling velocity available in literature so far.A similar parameter β for calculating total suspension concentration is also developed.The classical Rouse equation is modified with β_n and β and used to compute grain-size distribution and total concentration in suspension,respectively.The computed values have shown good agreement with the measured values of experimental data.     

Quantitative analysis of the impact of droughts and floods on internal wars in China over the last 500 years

Although many large-N quantitative studies have evidenced the adverse effects of climatic extremes on social stability in China during the historical period, most of them rely on temperature and precipitation as major explanatory variables, while the influence of floods and droughts on social crises is rarely measured. Furthermore, a comparison of the climate-society nexus among different geographic regions and at different temporal scales is missing in those studies. To address this knowledge gap,this study examines quantitatively the influence of floods and droughts on internal wars in three agro-ecological(rice, wheat,and pastoral) regions in China in AD1470–1911. Poisson regression and wavelet transform coherence analyses are applied to allow for the non-linear and non-stationary nature of the climate-war nexus. Results show that floods and droughts are significant in driving internal wars in historical China, but are characterized by strong regional variation. In the rice region, floods trigger internal wars at the inter-annual and multi-decadal time scales. In the wheat region, both floods and droughts cause internal wars at the inter-annual and multi-decadal time scales. In the pastoral region, internal wars are associated with floods only at the multi-decadal time scale. In addition, the multi-decadal coherence between hydro-climatic extremes and internal wars in all three of the agro-ecological regions is only significant in periods in which population density is increasing or the upper limit of regional carrying capacity is being reached. The above results imply that the climate-war nexus is mediated by regional geographic factors such as physical environmental setting and population pressure. Hence, we encourage researchers who study the historical human-climate relationship to boil down data according to geographic regions in the course of statistical analysis and to examine each region individually in follow-up studies.     

Thermal Process in the Crust and Upper Mantle in Xingtai-Shulu area of Hebei Province,China

Study of geothermal field data,terrestrial heat flow values,and other geophysical data from the Xingtai-Shulu area of Hebei Province made us more understanding of the distribution of geothermal fields and deep structures and their interrelation.The study illustrates that the geothermal field has an apparent lateral inhomogeneity and is evidently correlated by the structure of the crust and upper mantle in the area.The relation of the geothermal field distribution to the structure indicates that in comparison with the depression zone,the uplift zone has a higher heat flow value and a larger geothermal gradient.The analysis of the relation between distribution of earthquake epicenters and geothermal field and mathematical simulation of thermal stress in the area suggests that thermal stress plays an important role in the process of earthquake generation.     

Mesozoic tectono-magmatic activities in South China:Retrospect and prospect

The South China Block was formed through the collisional orogeny between the Cathaysia Block and the Yangtze Block in the Early Neoproterozoic.The northern,western and southern sides of the South China Block were affected by disappearance of the Paleo-Tethyan Ocean during the Paleozoic.The southern and northern sides of the South China Block were respectively collided with the Indo-China Block and North China Block in the latest Paleozoic to form the basic framework of the Eastern China.The Eastern China has been affected by the westward subduction of the Pacific Plate since the Mesozoic.Therefore,the South China Block was influenced by the three major tectonic systems,leading to a superposed compound tectonics.The comparative study of the Mesozoic geology between the South China Block and its surrounding areas suggests that although the Mesozoic South China Block was adjacent to the subduction zone of the western Pacific,no juvenile arc-type crust has been found in the eastern margin.The main Mesozoic geology in South China is characterized by reworking of ancient continental margins to intracontinental tectonics,lacking oceanic arc basalts and continental arc andesites.Therefore,a key to understanding of the Mesozoic geology in South China is to determine the temporal-spatial distribution and tectonic evolution of Mesozoic magmatic rocks in this region.This paper presents a review on the tectonic evolution of the South China Block through summarizing the magmatic rock records from the compressional to extensional tectonic process with the transition at the three juncture zones and using the deformation and geophysic data from the deep part of the South China continental lithosphere.Our attempt is to promote the study of South China’s geology and to make it as a typical target for development of plate tectonic theory.     

呼和浩特—包头地区平均波速比研究

The geological structure is complex in the Hohhot-Baotou area.Several earthquakes with MS≥6.0 have occurred in the area in history.This article selected the Hohhot-Baotou area as the study region and divided it into 2 sub-regions,each with a spatial scope of 3°×2°,according to the spatial distribution of ML≥1.0 earthquakes occurring between January 2001 and April 2010,and the layout of the seismic network in the study region.Average velocity ratios of respective sub-regions were calculated,and comparative analysis was made on their temporal and spatial variations.Results show that there are slight differences between sub-regions in the variation amplitude of average velocity ratio curves over time,which mostly remains between 2.5% to 2.584%.In the Hohhot area,the average velocity ratio is 1.722,significantly lower than the average velocity ratio of 1.733 in the Baotou area.We preliminarily concluded that this was related to the distribution of fault structures and properties of underground media in the Hohhot area.