共查询到19条相似文献，搜索用时 140 毫秒
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跨断层地形变观测对于寻找强震前兆异常、分析孕震机理、研究区域地球动力学等具有重要的科学意义。本文在分析传统短水准、短基线跨断层地形变观测技术的发展和主要不足的同时,比较详细地介绍了我国自行研制的MD数字化跨断层地形变自动观测仪器的应用,以及EDM全自动激光测距、GPS、D-InSAR等几种国际上最新的跨断层地形变观测技术。文中还从监测能力、观测精度、信息特征等角度,对这几种主要的跨断层地形变观测技术进行了较为全面的总结和讨论。 相似文献
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张永海 《西安地质学院学报》2009,(3):327-330
GPS技术在大地测量、维护大地坐标系和进行全球板块运动或区域地壳形变监测中已得到非常广泛的应用,但在城市地面沉降监测方面,仍存在基准选取、系统参数对高程形变影响等问题。比较了平差过程中的不同基准模型,分析了各自的适用性,讨论了系统参数对平差结果的影响,得出附加系统参数和附有约束条件的网平差计算模型,最后对西安地区布设的GPS地面沉降和地裂缝监测网进行计算,比较了不同的平差方案,得出系统参数和不同基准模型对地面沉降数据处理的影响和适用性。 相似文献
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数字化形变台站日常下载、处理直至管理数据,都应用《数字化通讯控制软件》、《形变前兆台站(网)数据处理系统》及《形变前兆数据库服务软件(台站版)》等三个软件交互进行,在实际使用过程中会遇到一些棘手的问题。本文结合我台的观测工作的实践,总结经验,以供台站同行共享。 相似文献
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数字化形变台站日常下载、处理直至管理数据,都应用《数字化通讯控制软件》、《形变前兆台站(网)数据处理系统》及《形变前兆数据库服务软件(台站版)》等三个软件交互进行,在实际使用过程中会遇到一些棘手的问题。本文结合我台的观测工作的实践,总结经验,以供台站同行共享。 相似文献
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本文在关中盆地现有监测网的基础上,基于GIS技术,采用建设监测剖面与编制地下水动态类型图相结合的方法,对关中盆地地下水动态监测网进行了优化调整,形成4横5纵共9条监测剖面、239个监测点的地下水动态监测网,其中潜水监测井120个,承压水监测井119个;利用原有监测井165个,新增监测井74个。新建监测网能够较全面地控制关中盆地区域地下水动态变化,在2011年＂严重缺水地区地下水监测项目＂中,以动态监测数据为依据,确定了主要干旱区位置,为政府应急抗旱找水打井提供了技术支撑。 相似文献
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淄博市大武水源地是中国北方罕见的特大型岩溶-裂隙地下水水源地,地下水开采量为52×10~4m~3/d。为了对岩溶地下水进行有效监测,需要建立最优的地下水监测网。文中在对岩溶地下水流系统分析的基础上,建立了地下水流系统确定性-随机性数学模型,运用有限元与卡尔曼滤波耦合的模拟递推算法,对大武水源地地下水监测网进行了优化设计,结果显示:现有地下水位动态监测网难以达到监测目标,最优地下水位监测网由14个监测井,每月监测一次的监测频率组成,比现有地下水位监测网减少了2个监测井。 相似文献
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Thermal Anomalies In A Regional Metamorphic Terrane: An Isotopic Study of the Role of Fluids 总被引：1，自引：1，他引：1
A series of ten localized, high-temperature, granulite faciesregions occurs within the regional metamorphic, sillimanitezone of New Hampshire, USA. These regions, or ‘hot spots’,measure 10–30km2 in a sillimanite zone that extends 50kmeast-west and over 150km north-south. The hot spots are characterizedby an abrupt increase in temperature over a distance of a fewkilometers, from 550?C in the sillimanite zone to 700?C in thegranulite facies. Mineral assemblages in pelites change rapidlyover the same distance from sillimanite-staurolite-muscovite-garnet-biotite-quartzto sillimanite-K feldspar-cordierite-garnet-biotite-quartz inthe granulite facies. The hot spot located near Bristol, New Hampshire was chosenfor detailed study because it has a network of quartz-graphiteveins in its core. Oxygen isotope analyses of minerals and rocksfrom Bristol suggest a close approach to pervasive exchangeequilibration between disparate rock types throughout the sillimanitezone. A comparison between chlorite zone pelites and calc-silicategranofelses of equivalent stratigraphic age shows a range ofover 7 in 18O of whole rocks from lower grade, whereas sillimanitezone rocks from Bristol vary by no more than 3, only. Quartzseparated from the Bristol high-grade metasediments varies byno more than 2?3. Superimposed upon the regional, sillimanite-zone oxygen isotopehomogenization is a 1–2 km wide region in the core ofthe hot spot in which the 18O of metasediments has been furtherhomogenized. Both quartz from quartz-graphite veins and quartzfrom cordierite-bearing wall rocks have exchanged oxygen isotopes;all quartz has 18O=13?8?0?5 (SMOW). Radiometric ages of quartz-graphite veins and metasedimentarywall rocks show that the hydrothermal event and metamorphismin the hot spot were both of Acadian age. Hydrothermal overgrow-thson zircons from one of the veins give ages of 409 ? 6 Ma. Monazitefrom cordierite bearing pelites from the wall of the same veingives a U-Pb age of 392 ? 3 Ma, using conventional techniques. The coincidence of: (1) an isograd high; (2) an isotherm hotspot; (3) a network of quartz-graphite veins; and (4) an oxygenisotope alteration halo suggests a relationship between hydrothermalactivity and heating of metasediments. The geochronologicalevidence demonstrates that the hydrothermal event and hot spotmetamorphism were not greatly separated in time. It is proposedthat the hot spots represent loci where hot metamorphic fluidswere focused through a fracture system now recorded by quartz-graphiteveins. 相似文献
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The present work reports on the isotopic characterization of rainfall and groundwater at Mt. Vesuvius. Values of δ 18O, monthly measured on rain samples collected during the period 2002–2004 in a rain-gauge network composed of 10 stations, were compared with meteorological and DEM data. Air temperature, controlled by the local orographic structure, was identified as the main factor influencing rain isotopic composition. Another important role is played by orographic clouds, whose condensation over the top of Mt. Vesuvius is responsible for anomalously high δ 18O values recorded in rain samples from the summit area of the volcanic edifice. A spatial model of rain isotopic composition, based on a 3D distribution of temperature derived by a 1 × 1 km DEM, was implemented and used for calculating the theoretical isotopic signature of seepage, further compared with data measured in the groundwater monitoring network. The analysis evidenced the role of local meteoric recharge as the main source feeding Mt. Vesuvius aquifers. The unique exception is the Olivella drainage gallery, located on the north-eastern flank of the volcanic edifice, whose isotopic composition is slightly more positive than the one expected for its altitude, likely caused by both evaporation processes and mixing with condensed hydrothermal vapor. 相似文献
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The effects of the addition of Al2O3 on the large stable two liquid field in the SiO2-TiO2-CaO-MgO-FeO system were experimentally determined. The increase of Al2O3 content in the starting composition results in the decrease of critical temperature, phase separation and liquidus temperature of the two liquid field until it is rendered completely metastable. The shrinkage of the two liquid field indicates that Al2O3 is acting in the role of a network former and homogenizes the structure of the two melts. In this alkali-free system Al+3 utilizes the divalent cations, Ca+2 and Mg+2, for local charge balance with a preference for Ca+2 over Mg+2. Thus, AlO4 tetrahedra combine with SiO4 tetrahedra to form an aluminosilicate framework which polymerizes the SiO2-poor melt and makes it structurally more similar to the SiO2-rich melt. However, Ca+2 and Mg+2 are not as efficient in a charge balancing capacity as the monovalent K+ and Na+ cations. The lack of alkalis in this system limits the stability of AlO4 tetrahedra in the highly polymerized SiO2-rich melt and results in the preference of Al2O3 for the SiO2-poor melt. The partitioning systematics of Ti are virtually identical to those of Al. It is concluded that Ti occurs in tetrahedral coordination as a network forming species in both the high — and low — SiO immiscible melts. 相似文献
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The investigation throughout the world in past two decades provides evidence which indicate that significance variation of radon and other soil gases occur in association with major geophysical events such as earthquake. The traditional statistical algorithm includes regression to remove the effect of the meteorological parameters from the raw radon and anomalies are calculated either taking the periodicity in seasonal variations or periodicity computed using Fast Fourier Transform. In case of neural networks the regression step is avoided. A neural network model can be found which can learn the behavior of radon with respect to meteorological parameter in order that changing emission patterns may be adapted to by the model on its own. The output of this neural model is the estimated radon values. This estimated radon value is used to decide whether anomalous behavior of radon has occurred and a valid precursor may be identified. The neural network model developed using Radial Basis function network gave a prediction rate of 87.7%. The same was accompanied by huge false alarms. The present paper deals with improved neural network algorithm using Probabilistic Neural Networks that requires neither an explicit step of regression nor use of any specific period. This neural network model reduces the false alarms to zero and gave same prediction rate as RBF networks. 相似文献
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Annamaria Fornelli Antonio Langone Francesca Micheletti Giuseppe Piccarreta 《Mineralogy and Petrology》2011,103(1-4):101-122
The lower crust of the Serre massif (Calabria, southern Italy) provides a window into the mid- to lower crust of the south European Variscan orogenic belt. Previously, zircon U-Pb ages were employed to date high-temperature processes affecting this portion of the Variscan crust. The present paper reports new LA-ICP-MS U-Pb data on the zircon of a deformed quartz-monzodiorite dike and of three mafic granulites sampled at the base of the lower crust section. Determination of trace elements on zircon, including rare earth elements (REE), has been also performed. The end of the Variscan exhumation, dated by anatectic zircon from migmatitic metapelites, and the growth-modification of zircon with respect to the growth of Variscan metamorphic garnet have been assumed as ??time markers??. The concordant zircon ages of the metamorphic basic rocks cover a range from 744?±?20 Ma to 231?±?10 Ma with high age density from 357?±?11?Ma to 279?±?10 Ma, a few ages comprised between 418?±?14 Ma and 483?±?12 Ma and between 505?±?11 Ma and 593?±?14 Ma. Zircon from the deformed quartz-monzodiorite dike evidences a minimum age of emplacement of 323?±?5 Ma. Most of the analysed zircon domains dated between 357?±?11 Ma to 279?±?10 Ma from garnet-bearing metabasic rocks show flat patterns of heavy rare earth elements (HREE), as expected in the case of their simultaneous growth with garnet. This allows to consider (1) zircon domains giving Variscan ages as ??metamorphic?? with specific geological significance, and (2) zircon domains with ages ranging from 564?±?17 Ma to 593?±?14 Ma as dating the emplacement of the magmatic protoliths as shown by internal microtextures, fractionated patterns of HREE and Th/U ratios (0.16?C0.19). The Variscan zircon ages (357?C279?Ma) reflect effects of crustal thickening, peak metamorphism and subsequent multistage Variscan decompression documented by the statistically significant clusters of ages around 347?C340?Ma, 323?C318?Ma, 300?C294?Ma and 279?Ma. The U-Pb zircon ages of the metabasic rocks suggest a period of about 60?C70?Ma for granulite facies metamorphism and anatectic conditions. Literature data indicate that the migmatitic metapelites of the upper part of the Serre crust section also underwent a long period, about 40?Ma, of granulite facies metamorphism and anatectic conditions. A diachronism emerges through the time comparison of the Variscan evolution between the upper and the lower portions of the Serre deep crust. The duration of the Variscan processes defined in Calabria is comparable to that of other south European Variscan blocks. 相似文献
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The solubility mechanism of fluorine in quenched SiO2-NaF and SiO2-AlF3 melts has been determined with Raman spectroscopy. In the fluorine abundance range of F/(F+Si) from 0.15 to 0.5, a portion of the fluorine is exchanged with bridging oxygen in the silicate network to form Si-F bonds. In individual SiO4-tetrahedra, one oxygen per silicon is replaced in this manner to form fluorine-bearing silicate complexes in the melt. The proportion of these complexes is nearly linearly correlated with bulk melt F/(F+Si) in the system SiO2-AlF3, but its abundance increases at a lower rate and nonlinearly with increasing F/(F+Si) in the system SiO2-NaF. The process results in the formation ofnonbridging oxygen (NBO), resulting in stabilization of Si2O 5 2? units as well as metal (Na+ or Al3+) fluoride complexes in the melts. Sodium fluoride complexes are significantly more stable than those of aluminum fluoride. 相似文献
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An artificial neural network (ANN) toolbox is created within GIS software for spatial interpolation, which will help GIS users to train and test ANNs, perform spatial analysis, and display results as a single process. The performance is compared to that of the open source Fast Artificial Neural Network library and conventional interpolation methods by creating digital elevation models (DEMs) given that nearly exact solutions exist. Simulation results show that the advanced backpropagations such as iRprop speed up the learning, while they can get stuck in a local minimum depending on initial weight sets. Besides, the division of input–output examples into training and test data affects the accuracy, particularly when the distribution of the examples is skewed and peaked, and the number of data is small. ANNs, however, show the similar performance to inversed distance weighted or kriging and outperform polynomial interpolations as a global interpolation method in high-dimensional data. In addition, the neural network residual kriging (NNRK) model, which combines the ANN toolbox and kriging within GIS software, is performed. The NNRK outperforms conventional methods and well captures global trends and local variations. A key outcome of this work is that the ANN toolbox created within the de facto standard GIS software is applicable to various spatial analysis including hazard risk assessment over a large area, in particular when there are multiple potential causes, the relationship between risk factors and hazard events is not clear, and the number of available data is small given its performance for DEM generation. 相似文献
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In this study, stochastic finite fault modeling is used to simulate Uttarkashi (1991) and Chamoli (1999) earthquakes using all available source, path, and site parameters available for the region. These two moderate earthquakes are recorded at number of stations of a strong motion network. The predicted peak ground accelerations at these stations are compared with the observed data and the ground motion parameters are constrained. The stress drop of Uttarkashi and Chamoli earthquakes is constrained at 77 and 65?bars, respectively, whereas the quality factor Q C is 112 $ f^{0.97} $ and 149 $ f^{0.95} $ for these two regions. The high-frequency attenuation parameter Kappa is in the range 0.04?C0.05. The constrained ground motion parameters are then used to simulate Mw 8.5 earthquake in central seismic gap region of Himalaya. Two scenarios are considered with epicenter of future great earthquake at locations of Uttarkashi and Chamoli earthquakes using above constrained parameters. The most vulnerable towns are the towns of Dehradun and Almora where expected PGA is in excess of 600?cm/s2 at VS30 520?m/s when the epicenter of the great earthquake is at the location of Uttarkashi (1991) earthquake. The towns of Shimla and Chandigarh can expect PGA close to 200?cm/s2. Whereas when the epicenter of the great earthquake is at the location of Chamoli (1999) earthquake, the towns of Dehradun and Almora can expect PGA of around 500 and 400?cm/s2, respectively, at VS30 620?m/s. The National Capital Region, Delhi can expect accelerations of around 80?cm/s2 in both the cases. The PGA contour maps obtained in this study can be used to assess the seismic hazard of the region and identify vulnerable areas in and around central Himalaya from a future great earthquake. 相似文献
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为解决岩溶高原山区缺水的问题,合理开发利用表层岩溶水,开展了水文地质详细调查。查明区内表层岩溶泉出露13个,流量0~67.53 L·s?1,动态变化与降水关系密切。文章总结了表层岩溶水“泉－池（窖）－库”优化调控、绿能高效开发利用模式:①在有砂泥岩夹层分布的凹部山岩溶洼地,采用防渗帷幕灌浆,建设悬挂式凹部山水库,积蓄地表水、表层岩溶水形成自流供水;②在湾半孔表层泉处建设蓄水池直接引流利用;③在湾半孔表层泉附近建设水泵站、光伏电站,平水期时通过光伏电站发电,由泵站自动控制抽取表层岩溶水补给凹部山水库,形成地表、地下水优化调控,联合调度调蓄利用25.3万m3·a?1,解决了区内13 000余人的生活生产用水困难问题。 相似文献