A geophysical study of the granites and the sedimentary basins of the Xanthi area (N. Greece)

Intrusive features of varying size can be interpreted from the aeromagnetic map of the Xanthi area in N. Greece.The Xanthi pluton, which outcrops north of the city of Xanthi, seems to have the shape of a truncated pyramid. This feature has relatively large areal extent and reaches an approximate depth of 7 km. Another, relatively large magnetic body is buried under the sediments at the estuary of the Nestos River.3-D models of several smaller intrusions were constructed and the produced effect was compared to the observed. Some of these intrusions seem to be detached branches of the large Xanthi pluton.The basement in the outer part of the basin of the Nestos River seems to be buried at about 4 km depth. This figure is obtained by the Multiple Source Werner Deconvolution estimates and it is in agreement with the results of former geophysical studies and deep industrial boreholes.A 3-D model of the Xanthi-Komotini basin suggests that this basin is about 0.4 km deep at its southern part. The depth at its northern boundary is about 1.8 km while the boundary itself is formed by the large Kavala-Xanthi-Komotini fault.The Tertiary basin of the Nestos River and the observed magmatism are consistent with the idea of an older extensional tectonic regime in the area.     

EFFECT OF TIDAL FLOW ON ESTUARINE SEDIMENTATION

1. INTRODUCTIONIn the regulation of an estuary and the maintenance of a tidal channel for navigation, it is highlyimportant to investigate the interplay between tide and river flow and to anticipate its effects on sedimentation. In this paper. sediment--laden flow in an estuary is treated as a case of two--phase flow. resulting in a set of four governing equations. A theoretical solution is then derived for a simplified casefor qualitative assessment. Numerical computations are also carri…     

ON THE USE OF MOVABLE-BED MODELS FOR RIVER PROBLEMS:A STATE-OF-THE-ART

I. INTRODUCTIONMore than a decade ago, under tile auspices of DELFT HYDRAULICS an overview on the use ofmodels for river problems was given (de Vries & van der Zwaard. 1975). Since then a better understanding of morphological processes in rivers has been obtained, their mathematical formulation hasbeen improved and computer facilities have been expended. Scale models and mathematical models arein use. but their field of application is gradually changing. It seems that the better ma…     

Eruption dynamics of the SW crater of Stromboli volcano,Italy — An interdisciplinary approach

We report on the evaluation of in situ measurements of eruption velocities and relative mass flux, collected by Doppler radar, as well as acoustic and infrared data, that were recorded at Stromboli volcano. Doppler radar observations were made alongside thermal, acoustic and seismic measurements, to (1) further investigate the complex waveforms of the SW crater by combining infrasonic, infrared and Doppler radar measurements, (2) establish a relationship between infrared, acoustic and Doppler radar measurements and (3) verify that all instruments observe the same behavior in terms of relative mass eruption rate. We also explore the relationship between kinetic and acoustic energy released during an eruption. Comparing the different methods to each other we are able to show that the mass erupted can be estimated either from the total reflected Doppler radar energy or from infrared observations. However, neither thermal nor reflected energy can provide a value in terms of absolute mass in kg. The erupted masses of different eruptions can only be evaluated relative to each other. Using the combined three data sets we especially focus on the eruption dynamics of the SW crater of Stromboli, namely its fluctuations in eruption strength. These pulses in one eruptive event, so called ’pulsations’ dominate more than 40% of the eruptions of SW crater. Previous models that explain pulsations to be generated by multiple consecutively exploding bubbles are supported by our combined analysis of infrasound, thermal data, particle velocities, and the reflected energy.     

Hydro-meteorological drought assessment under climate change impact over the Vu Gia–Thu Bon river basin,Vietnam

Hydro-meteorological drought was assessed with respect to climate change over an estuary catchment Vu Gia-Thu Bon in Central Vietnam, which economy is dependent on agriculture. The fully-distributed hydrological model MIKE SHE was used to simulate river flow over the study region for the period 1991–2010. Drought were assessed using the Standardized Precipitation Index and the Standardized Runoff Index. The future climate was studied using the regional climate model Weather Research and Forecasting by downscaling an ensemble of three global climate models – CCSM3.0, ECHAM5 and MIROC-medium resolution over current (1961–1990) and future climates (2011–2040), under the A2 emissions scenario. The results suggest that, despite hotter and wetter future climate, the area is likely to suffer more from severe and extreme droughts, increasing about 100% in the median range for drought characteristics. Thus, there is a need for proper adaptation and planning for water resources management in this region.     

Flow patterns in temporary rivers: a methodological approach applied to southern Iberia

Temporary flow patterns remain understudied, despite their wide distribution and their importance for managerial practices and river conservation. This paper explores an advanced procedure for the characterization and definition of temporary flow patterns based on the frequency, duration and magnitude of non-flow (cessation) periods. A detailed analysis of flow patterns was performed on 12 rivers of the Guadiana Basin in Southern Iberia (10 in Spain and 2 in Portugal). An open methodology that can allow managers to better characterize and improve the structure and functioning of those rivers is suggested. This methodology is based on inter- and intra-annual variability analysis and its integration with river ecotypes. Within the methodology, a set of parameters related to ecological features of temporary rivers is proposed for application. This methodology may contribute to a better definition of cessation periods and an integrated understanding of the flow requirements of temporary rivers.     

MOVING AND STAGNATION OF DEBRIS FLOW

LINTRODUCTIONThedebrisflowisaverycomplexflow.Itdiffersfromwaterflowandsuspendedflowinmovingandstagnation.Thedebrisflowisgenerallydiscribedasthegravityflowofsoil.rock,waterandinitiatedbylandslide,usuallyduetohighrunoffflow.Theoccurrenceofdebrisflowisratherunpredictableandverydestwhve.Debrisflowcouldmovefasterthanthemorecommonlandslideandtendto~tareasatmuchgreaterdistancefromthesourceofhazard.Debrisflowdisastershavebeenrecognizedasacriticalproblemfacingtheworldtodayandincreasingattentionha…     

多分辨分析理论在井-震匹配中的应用

简单介绍了多分辨率逼近理论,详尽分析了地震与声测井资料在尺度上的差异,进而提出了一种解决井-震尺度差异的新方法--多分辨率逼近方法。通过理论模型及实际资料算例验证了该方法的有效性,并且与常用的抗混频滤波方法进行了比较。结果表明,多分辨率逼近方法更能保持信号的局部化性质,使地震与声波测井资料能更好地匹配。     

Ecohydrological effects of water reservoirs with consideration of asynchronous and synchronous concurrences of high- and low-flow regimes

Inflow of nine reservoirs in the Liao River basin, China, is used to analyse the concurrence of high/low flows, and also the ecological instream flow. The results indicate that the general extreme value distribution model performs well in describing the probabilistic behaviour of high/low flows in the basin. Specifically, the Gumbel and Frank copula functions perform better than other functions. Reservoir inflow encounter series are subject to high synchronous concurrence, at greater than 27% for low flow vs low flow. Thus, the water supply system of the basin is not steady. The ecological instream flow can be analysed by a monthly frequency computation method, with 90% guarantee rate. The low-flow periods are January, February and May, and water transfers are not feasible in these periods. Thus, external sources of water are urgently needed to guarantee sufficient water supply to provide critical water resources and to protect important aquatic environments.     

中国古代中心日食记载与地球自转速率的变化

利用中国古代中心日食（全、环食）的观测记载研究近2千余年间地球自转速率长期变化的原理和方法,讨论了中国古代中心日食和近中心日食观测的记载资料,并利用其中可靠的记载和-26.0″/（100a）²的月球本征加速度值计算得到了表示地球自转长期变化的△T值系列,由此得到表示地球自转长期减慢的日长变化均值约为1.4ms/100a,该平均值相应的历元为A.D.1141。     

The role of soil moisture initialization in subseasonal and seasonal streamflow prediction – A case study in Sri Lanka

The two main contributors to streamflow predictability at subseasonal to seasonal timescales in tropical regions are: (i) the predictability of meteorologic (particularly precipitation) anomalies, and (ii) the land surface soil moisture state at the start of the forecast period. Meteorological predictions at subseasonal timescale are usually fraught with error and may not be dependable. The accurate initialization of soil moisture, as obtained through real-time land data analysis, may provide skill in subseasonal to seasonal streamflow prediction, even when the prediction skill for rainfall is small.     

NUTRIENT LOAD ESTIMATION METHODS FOR RIVERS

Pollutant load estimation is essential for watershed management and water pollution control. For most watersheds, only sparse water quality measurements (e.g. monthly data) are available. The influence of input data on the accuracy of non-point source pollution load estimation is studied using the water quality and stream flow data from a small watershed in Hong Kong. Comparison and analysis of the results using 8 different methods show that the accuracy of stream-flow runoff is the single most important factor for the calculation of pollutant load. Based on the results, the stream flow correction coefficient is advanced to provide a more reliable load estimation. The improved method of pollutant load estimation can be easily applied in practice since the stream-flow runoff can be measured by hydrological station or estimated with various hydrological methods.     

Optimum multiple tuned mass dampers for structures under the ground acceleration based on DDMF and ADMF

Multiple tuned mass dampers (MTMD) consisting of many tuned mass dampers (TMDs) with a uniform distribution of natural frequencies are taken into consideration for attenuating undesirable vibration of a structure under the ground acceleration. A study is conducted to search for the preferable MTMD which performs better and is easily manufactured from the five available models (i.e. MTMD‐1 – MTMD‐5), which comprise various combinations of the stiffness, mass, damping coefficient and damping ratio in the MTMD. The major objective of the present study then is to evaluate and compare the control performance of these five models. The structure is represented by its mode‐generalized system in the specific vibration mode being controlled by adopting the mode reduced‐order approach. The optimum parameters of the MTMD‐1 – MTMD‐5 are investigated to reveal the influence of the important parameters on their effectiveness and robustness using a numerical searching technique. The parameters include the frequency spacing, average damping ratio, tuning frequency ratio, mass ratio and total number. The criteria selected for the optimum searching are the minimization of the maximum value of the displacement dynamic magnification factor (DDMF) and that of the acceleration dynamic magnification factor (ADMF) of the structure with the MTMD‐1 – MTMD‐5 (i.e. Min.Max.DDMF and Min.Max.ADMF). It is demonstrated that the optimum MTMD‐1 and MTMD‐4 yield approximately the same control performance, and offer higher effectiveness and robustness than the optimum MTMD‐2, MTMD‐3, and MTMD‐5 in reducing the displacement and acceleration responses of structures. It is further demonstrated that for both the best effectiveness and robustness and the simplest manufacturing, it is preferable to select the optimum MTMD‐1. Copyright © 2002 John Wiley & Sons, Ltd.     

Evidences for a low-velocity core-mantle transition zone

Using the spectral ratios $\text{P}\text{PcP}\text{,}\text{ScS}{}_{\mathrm{n+1}}\text{ScS}{}_{\mathrm{n}}\text{,}\text{sScS}{}_{\mathrm{n+1}}\text{sScS}{}_{\mathrm{n}}\text{and}\text{SKS}\text{ScS}$, models for the core-mantle boundary are found. The models have close similarity with each other, implying an irregular surface with lateral variation in the core-mantle properties. The models are characterized by two to four low-velocity, high-density layers imbedded between the mantle and the core half space. The velocities of the imbedded layers decrease towards the core boundary with a lower bound of 9.3 km/sec for the compressional wave and 3.5 km/sec for the shear wave. The models fitted to the empirical data support the hypothesis of a finite rigid outer core with a higher bound for the shear velocity of 1.4 km/sec. Based on this finite rigidity in the outer core and a layered core-mantle transition zone, the value of Q for the whole mantle is 2,000. For the outer core Q ranges from 100–1,000 , which may indicate that it is chemically zoned.     

图象识别方法在工程地震学中的应用

本文讨论图象识别方法在工程地震学中应用的现状及前景。首先简略介绍算法的基本原理及对算法的改进,然后作为新研究成果的介绍论述了图象识别方法在确定潜在震源区、砂土液化势方面的应用以及用C-拓扑模糊决策分类系统——一种新的动态分类系统去估计潜在震源区随时间变化发震能力——地震势的方法     

地球远磁尾中的磁场重联——（Ⅱ）局部驱动力的影响

基于可压缩磁流体动力学模型,数值研究了由太阳风引起的局部驱动力对地球远磁尾中磁场重联的影响.结果表明,在远磁尾等离子体片中将发生强迫磁场重联,并形成磁岛和等离子体团.形成磁岛的特征时间很大于流动撕裂模不稳定性引起磁岛非线性饱和的特征时间.磁岛宽度随着磁Reynolds数S的增大而减小,随着尾瓣中等离子体压力与磁压之比值β_∞的降低而减小.认为太阳风引起的局部驱动力对地球远磁尾等离子体片中磁场重联的影响,可能不如流动撕裂模不稳定性那样显著.     

山西断陷盆地带形成机制的初步数值模拟

本文在分析山西断陷盆地带的各种地质、地球物理资料的基础上,用三维粘-弹塑性有限元方法对该断陷带的形成机制进行了模拟计算。表明山西断陷盆地带的形成是地壳深部的上隆作用和北东—南西向挤压应力场在深部隐伏断裂上派生的右旋滑动共同作用的结果。地壳深部的上隆是一个主要的不可忽视的因素