Contributions of phosphatase and microbial activity to internal phosphorus loading and their relation to lake eutrophication

Phosphatase may accelerate the process of lake eutrophication through improving phosphorus bioavailability. This mechanism was studied in three Chinese eutrophic shallow lakes (Lake Taihu, Lake Longyang and Lake Lianhua). Phosphatase activity was related to the concentration of soluble reactive phosphorus (SRP) and chlorophyll a. Stability of dissolved phosphatase in reverse micelles may be attributed to molecular size, conformation and active residues of the enzyme. At the site with Microcystis bloomed in Lake Taihu, dissolved phosphatase activity was higher and more stable in micelles, SRP concentrations were lower in interstitial water, the contents of different forms of phosphorus and the amounts of aerobic bacteria were lower while respiration efficiency was higher in sediments. Phosphobacteria, both inorganic and organic and other microorganisms were abundant in surface water but rare in sediments. Therefore, internal phosphorus may substantially flux into water column by enzymatic hydrolysis and anaerobic release, together with mobility of bacteria, thereby initiating the bloom. In short, biological mechanism may act in concert with physical and chemical factors to drive the internal phosphorus release and accelerate lake eutrophication.     

Application of the Linearity Method to Processing and Analyzing of Precursory Data

In this paper,the spatial linearity method is applied to synthetical processing of precursory data from different stations and different disciplines.The new characteristic value(a)obtained can describe the whole precursory field.The authors present the formulas for calculating spatial linearity.Furthermore,the spatial linearity method is applied to processing of geoelectrical resistivity and groundwater level data from 1970 to 1994 in North China.The results show that the new characteristic value(a)could detect the anomaly 1 year before moderately strong earthquakes.     

Application of mechanical and statistical models to the study of seismicity of syn-thetic earthquake

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Short-term and imminent anomalies of earthquake of load and unload response ratio of the well level to earth tides

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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     

Evaluation of Probabilistic Earthquake Prediction and Decision-making of Releasing Predictions to the Public

Chinese seismologists have been coping with the challenging scientific problem of earthquake prediction,but now they are confronted with an even more challenging problem:figuring out a procedure of releasing a prediction to the public.In order to make the correct decision,in addition to the widely launched studies of seismic hazard and risk analysis,it is necessary to further study the social consequences of releasing an earthquake prediction to the public,and the possible economic cost of prevention countermeasures against earthquakes.It is also necessary to replace deterministic predictions by probabilistic predictions.Probabilistic prediction is a method well-suited for the prediction of chaotic seismic events.It can integrate the long-term risk estimate and short-term forecasting into a unified procedure,make quantitative analysis in decision-making on the release of predictions to the public,and achieve maximum beneficial social results of earthquake prediction.     

Application of genetic BP network to discriminating earthquakes and explosions

Introduction Artificial Neural Network (ANN) is an important branch of artificial intelligence. It is proposed on the foundation of the study on modern neural science, is a man-made network that can implement some functions based on the mans comprehensive understanding for cerebral neural network (HAN, WANG, 1997). ANN is a mathematical model of simplified human brain neural network and is used to simulate the structures and functions of human brain neural network. ANN is a complex netw…     

Application of Correlation and Coherency Methods to Naqu Seismic Array Design

INTRODUCTIONFrom Aug.4 to Aug.26 ,2004 ,the Institute of Geophysics , China Earthquake Administrationcarried out a field survey in the Naqu district in Tibet ,in cooperation with the Beijing EarthquakeAdministration.10 stations were deployed with concentric circle methods for the field observation.Asthe result ,a large quantity of original waveformdata was recorded. Since the establishment of theNaqu seismic array will correspond withthe arraytype of the International Monitoring Sys…     

Cooling and crystallization of lava in open channels, and the transition of Pāhoehoe Lava to 'A'ā

 Samples collected from a lava channel active at Kīlauea Volcano during May 1997 are used to constrain rates of lava cooling and crystallization during early stages of flow. Lava erupted at near-liquidus temperatures (∼1150  °C) cooled and crystallized rapidly in upper parts of the channel. Glass geothermometry indicates cooling by 12–14  °C over the first 2 km of transport. At flow velocities of 1–2 m/s, this translates to cooling rates of 22–50  °C/h. Cooling rates this high can be explained by radiative cooling of a well-stirred flow, consistent with observations of non-steady flow in proximal regions of the channel. Crystallization of plagioclase and pyroxene microlites occurred in response to cooling, with crystallization rates of 20–50% per hour. Crystallization proceeded primarily by nucleation of new crystals, and nucleation rates of ∼10⁴/cm³s are similar to those measured in the 1984 open channel flow from Mauna Loa Volcano. There is no evidence for the large nucleation delays commonly assumed for plagioclase crystallization in basaltic melts, possibly a reflection of enhanced nucleation due to stirring of the flow. The transition of the flow surface morphology from pāhoehoe to 'a'ā occurred at a distance of 1.9 km from the vent. At this point, the flow was thermally stratified, with an interior temperature of ∼1137  °C and crystallinity of ∼15%, and a flow surface temperature of ∼1100  °C and crystallinity of ∼45%. 'A'ā formation initiated along channel margins, where crust was continuously disrupted, and involved tearing and clotting of the flow surface. Both observations suggest that the transition involved crossing of a rheological threshold. We suggest this threshold to be the development of a lava yield strength sufficient to prevent viscous flow of lava at the channel margin. We use this concept to propose that 'a'ā formation in open channels requires both sufficiently high strain rates for continued disruption of surface crusts and sufficient groundmass crystallinity to generate a yield strength equivalent to the imposed stress. In Hawai'i, where lava is typically microlite poor on eruption, these combined requirements help to explain two common observations on 'a'ā formation: (a) 'a'ā flow fields are generated when effusion rates are high (thus promoting crustal disruption); and (b) under most eruption conditions, lava issues from the vent as pāhoehoe and changes to 'a'ā only after flowing some distance, thus permitting sufficient crystallization. Received: 3 September 1998 / Accepted: 12 April 1999     

The pattern characteristics of the tendency variations of earth resistivity and its relation to earthquakes

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Response of Surface Soft Soil and Fine-Grained Sand Layers to Seismic Waves

INTRODUCTIONManyChineseandforeignseismologistsandengineeringseismologistshavestudiedthelargecasualtiesandpropertydamagescausedbytheMexicanMS8 1earthquakeonSeptember1 9,1 985andtheHanshinMS7 4earthquakeinJapan ,onJanuary 1 7,1 995andfoundthatsurfacesoftsoilcovercansignificantlyamplifyseismicgroundmotion .Thisphenomenoncanresultinlargerfailureofbuildingswithvibrationfrequencysimilartotheamplifiedgroundmotionfrequencythanthatcausedbyearthquakesthatoccuratbedrocksiteswheretherearenoamplifi…     

Co-seismic Water Level and Temperature Responses of Some Wells to Far-Field Strong Earthquakes and Their Mechanisms

The observation of water temperature in deep wells has been carried out for more than 20 years in China.However,study on the mechanism of water temperature response to earthquakes is inadequate.During the study of the co-seismic response characteristics of water level and temperature in 121 wells within the China subsurface fluid monitoring network at the time of the December 26,2004,M-S8.7 Indonesia earthquake,we found regular response characteristics,that is,when the water level in a deep well oscillates,the water temperature in the same well will mostly experience a cycle from dropping to restoration at the same time.The process will continue for dozens of minutes to several hours.In order to confirm the observed phenomenon,we collected the digital water level and temperature observation data for 39 far-field strong earthquakes from the Tangshan well in Hebei Province(with the data set beginning in 2001).The same response characteristics were observed.Based on the analysis of the influencing factors that may cause the water temperature drop,the authors suggest the gas escape mechanism for co-seismic water temperature drop and posit two main factors that influence the water temperature drop during the process of gas escape.Finally,the authors provide a rational explanation of some observed phenomena based on the mechanism.     

Effect of seasonal freeze–thaw process on spatial and temporal distribution of soil water and its infiltration to recharge groundwater

Clarifying the distribution and dynamics of soil moisture during the freeze–thaw process is crucial for surface ecology and is an objective requirement to investigate the mechanism of changes during the groundwater recharge process in a freeze–thaw zone. Based on the monitoring data of soil moisture and temperature in the Changbai Mountain area, the freeze–thaw process is classified into four periods. This study investigates the hydrothermal migration processes during different periods. The simultaneous heat and water model is used to simulate and analyse the infiltration of soil moisture into groundwater under five precipitation insurance rates. The results are as follows: (1) The smaller the soil depth, the stronger is the correlation between soil temperature and air temperature during the freeze–thaw process. (2) The redistribution of soil moisture before and after freeze–thaw is significantly affected by the soil texture, and soil permeability affects the recharge of soil moisture from the upper region to the lower region during the thawing period. (3) Groundwater receives vertical infiltration recharge mainly during non-freezing and is supplied by freezing and snowmelt recharge during the stable thawing period. The percentage of soil water infiltration during the stable thawing period in the total annual infiltration increases gradually with the precipitation insurance rate.     

Substructure Method of Three-Dimensional Semi-Analytic Boundary Element and Its Application to Seismic Scattering of Hill Topography

In this paper,a substructure method of three-dimensional semi-analytic boundary element is established.The seismic scattering by three-dimensional topography of a hill can be analyzed by the method in frequency domain.Using this method,the computational effort and storage space are reduced considerably.Finally,analytic results are given.     

Response of grain size of Quaternary gravels to climate and tectonics in the northern Tibetan Plateau

The widely distributed thick gravel deposits along the rim of the Tibetan Plateau have been long thought to be the product of rapid tectonic uplift of the plateau. However, this has been challenged by recent works that suggest these thick gravels may be the result of climate change. In this paper we carried out a detailed field measurement of gravel grain sizes from the Jiuquan and Gobi Gravel Beds in the top of the Laojunmiao section in the Jiuxi Basin in the northern margin of Qilian Mts. (northern Tibetan Plateau). The results suggest that the grain sizes of the Jiuquan and Gobi Gravel Beds over the last 0.8 Ma are characterized by nine coarse-fine cycles having strong 100-ka and 41-ka periodicities that correlate well with the loess-paleosol monsoon record and isotopic global climatic record from deep sea sediments as well as by a long trend of coarsening in gravel grain size. The coarse gravel layers were formed during the warm-humid interglaciations while the fine layers correspond to the cold-dry glaciations. Because the paleoclimate in NW China began to get dramatically drier after the mid-Pleistocene, we think the persistent coarsening of gravel grain size was most probably caused by the rapid uplift of the northern Tibetan Plateau, and that the orbital scale cyclic variations in gravel grain size were driven by orbital forcing factors that were superimposed on the tectonically-forced long-term coarsening trend in gravel size. These findings also shed new light on the interaction results of climate and tectonics in relation to the uplift of the Tibetan Plateau.     

Parameter estimation of the stochastic AMR model and its application to the study of several strong earthquakes

Introduction According to many published papers, seismicity in time-space domain shows some characteristics, such as doughnut epicenter distribution (Mogi, 1969) or quiescence of seismic activity before large earthquakes (WANG, et al, 2002), and aftershock decay (Ogata, 1998). In recent years, more and more seismologists (Lynnr, Steven, 1990) have found that many strong earthquakes are preceded by enhancing regional seismicity and accelerating strain energy release (ZHANG, et al, 2001). T…     

Fractal analysis applied to faults and earthquakes—A case study of China

The characteristics and correlation of faults and earthquakes are discussed based on fractal and statistical analysis of the earthquakes in the last 500 years and the active faults in China. It is found that fractal relationship exists between the frequency and the length of the active faults, and the fractal dimension is 1.70 in the continental region of China, and 1.40 in the northwest China. The fractal relationship also exists between the frequency and the scales of earthquakes during the last five centuries and the fractal dimension is 1.30 for the whole continental region of China and 1.08 for the northwest China. The differences of the fractal dimensions between the active faults and the earthquakes indicate that some of the active faults have not caused earthquakes during the last 500 years. The differences of fractal dimensions of the active faults and earthquakes between the northwest China and the whole continental region of China suggest that the frequency of strong earthquakes is greater in northwest China than that of the average level of China, because the number of longer active faults is larger in northwest China than that of the average in whole China. Thus, the fractal analysis is an effective method for studies of faults and earthquakes.     

Borehole Tilt Observations of Xiangshan Station, Beijing, and Effects of Tilt Due to Fault Creeping

An ASKANIA borehole tiltmeter which consists of a vertical pendulum with two degrees of freedom was installed in Xiangshan station,Beijing,in May 1989 in order to monitor the earthquake-reiated crustal deformations.The preliminary results indicate that the resolution of the instrument is better than 0.05 msec for tidal amplitudes.The daily total tidal amplitude is about 20 msec.The spectral analysis of the first four months data provides a signal-to-noise ratio of > 100 for the main semi-diurnal waves.The non-tidal tilts for one year data are dominated by a long term drift with the rate of 0.9 msec/day for X-component and 1.1 msec/day for Y-component.In addition,the tilt observations are affected by meteorological factors,especially by rainfall.The results of modelings of the fault-creep related tilts and responses of tilts to earthquakes suggest that the tilt measurements are very sensitive to the change in tectonic strain and stress fields near the site where the tiltmeter is installed.The fault-creep     

Theory and Experimental Results about the Application of Remote Sensing to Earthquake Prediction

In this paper,the theory for applying remote sensing to earthquake prediction has been elucidated and an experiment has been made.Through the experiment,it has been found that the characteristics and temperature of infrared radiant of rocks vary as a function of rock stress,the order of magnitude of radiance variation is 10-5(W/cm2 sr um),the amount of variation of the radiant temperature is 0.2℃~0.8℃ and some significant precursor information has been discovered.The experiment has verified preliminarily that the advanced technology of remote sensing can be applied to earthquake prediction.