中国新疆温泉、哈萨克斯坦地下流体观测资料前兆异常对比与分析

系统清理分析了中国新疆温泉台、哈萨克斯坦20多年地下流体观测资料.统计结果显示,中国新疆温泉台30井（泉）的氡、流量、水温,哈萨克斯坦卡帕尔井的氦气、扎尔甘特井的流量、博古特井水位、下卡姆井的氦气、萨雷扎斯井水位,映震率较高,在震前都有一定的震兆异常显示,而且前兆异常特征以高值异常为主,异常时间分布特征显示为短期异常.     

1990年乌苏5.2级地震前地下流体异常

１９９０年乌苏５．２级地震是北天山地区地下流体观测网改造以来，发生在监视区内的第一次中强地震。地震前出现了大面积、多井孔的地下流体异常，显示出了异常在空间上的一些变化。（１）震前异常形态复杂多样。由于不同的观测井其水文地质条件、水文地球化学环境以及观测参数本身的物理化学性质不同，表现出的异常形态也各不相同。另外，异常井孔的受力方式和受力性质的不同也是形成不同异常形态的重要原因。（２）位于震中区的观测井出现异常的比例显著高于外围地区；震中区异常出现时间较晚，外围地区异常出现较早，表现出异常从外围向震中迁移的变化图像。（３）与地震震中处于同一构造带的观测井（泉）容易受到震源应力的牵动和影响，出现异常的可能性大。     

地下流体前兆模糊识别

在地震的孕育、发生到发展的过程中，可能会出现多项地下流体观测量不同程度的前兆异常变化，这些异常变化是复杂多样、模糊不清的。引入模糊识别法对一定区域和一定时间段的地下流体观测数据进行了分析和处理，表明模糊识别法可较好地识别和分辨出地下流体前兆的地震异常。     

福建地下流体氟离子动态非地震前兆异常识别

2008年3—7月福建地区共发生4次中等地震,福建地下流体氟离子有多孔观测井,在震前或震后出现高值突跳的现象;2008年9-11月福建地下流体氟离子又有多孔观测井出现高值异常。本研究通过实验提出:该氟离子高值异常为非地震前兆异常,建议准备一支氟离子选择性电极作为备用电极,用于对比观测,以提高氟离子观测数据异常的判别。     

山东地震前兆台网地下流体数据跟踪分析

介绍了山东省地震前兆台网地下流体学科数据跟踪分析工作概况,从观测系统、自然环境、场地环境、人为干扰、地球物理事件、不明原因等方面分析了2015年1月至2017年6月跟踪到的非正常变化事件。通过数据跟踪分析,查明了山东区域前兆台网流体学科观测运行的制约因素,提出了合理化建议,以提高观测数据质量。并对荣成鲁32井水温观测数据出现的典型非正常变化事件进行了跟踪分析,判定其为地震前兆异常。     

地震前地下流体前兆异常特征的研究

针对鲁甸6.5级地震、唐山4.0级地震前地下流体异常现象,结合异常时段地下流体观测数据,对震前地下流体异常现象及指标进行总结分析。研究表明,鲁甸地震前及唐山地震前地下流体长期与中期异常特征均主要出现在距离震中心500 km范围内。地下流体震前异常特征现象观测的目的是判断地震危险区高密度观测特征,对地震高发区的中短期异常指标仅进行中短期分析。地震区域应力叠加导致地震前兆现象的开启,引起断裂带裂隙,地下水温度和地下深部气体异常变化,水岩变化使得地下流体混合前兆增强。在地震前兆观测范围内,获取地下流体异常指标变化可以为震前预测提供数据支持,推动地震预测理论的发展。     

地震地下流体观测现状

系统介绍我国地震地下流体井（泉）的分布现状、观测井含水层特征及自流热水井的观测现状,并介绍观测项目及主要观测仪器等。上述调查与分析结果,可为我国地震地下流体台网的进一步调整与优化,及今后地震地下流体学科的发展提供科学依据。     

盐津地震流体前兆异常分析

在分析了滇东北地区2006年7月22日、8月25日2次盐津5.1级地震前近震区和外围观测井点地下水物理、化学及断层气CO2异常基础上,总结了地下流体异常特征。研究结果表明:临近地震发生的短期阶段,流体前兆异常数量有增多的趋势;短临阶段在近震区附近出现宏观异常,异常点分布在距震中120 km范围内;从异常点的时空演化特征来看,距震中180km以内的观测井在震前异常显著,异常演化具有扩散、收缩现象;距震中180 km以外的2个二氧化碳观测点均表现为中短期异常,短临阶段有加速转折特征。由此可见,在地震孕育的短临阶段,地下流体微观异常与宏观异常的配套性综合分析是提高预测能力的重要依据。     

利用宁波水文地质监测井网建设地下流体前兆台阵的试验研究

从宁波水文地质监测井网中遴选了北仑井和慈溪井进行水位和水温试验性观测,分析计算水位的气压效率、降雨载荷效应和潮汐因子,并与同处于宁波盆地映震效果较好的庄市井的相应参数进行对比。结果表明：（1）3口水井的水位变化在时间上和空间上均有很好的相关性,水位异常动态与其影响因素之间存在很好的成因上的关联;（2）慈溪井的降雨载荷系数比庄市井和北仑井的大约小一个量级,这可能与慈溪井位于1960年代围海造田的滩涂地有关;（3）水井网均位于含有多个含水层的宁波盆地,为在同一构造中开展不同含水层观测和基础研究提供了可能,可以从井网中遴选出合格的地震前兆监测井,用于建设宁波盆地地震前兆流体台阵。     

试论"十五"期间我国地震地下流体前兆台网的优化与建设问题

根据我国地震地下流体前兆台网的现状、“九五”台站建设取得的进展与存在的问题,提出“十五”期间有关台网优化与建设方面的如下工作建议：（1）优化现有的台网;（2）完善与推广数字化观测技术,力争使经过数字化改造的台站数量由100个扩展到300个,实现数字化观测的台项由300个增加到10000个,基本实现我国流体前兆观测技术的现代化;（3）建设以地震监测与预测研究为目的前兆实验场。（4）建成地下流体学科技术中心;（5）建设重大工程的地震安全性监测系统。     

地震地下流体井水位、水温观测数据集

地震地下流体井水位、水温观测是地震地球物理台网主要观测手段,其数据集包含水位、水温测项的原始数据、预处理数据、产品数据和均值类数据,可为地震监测预报研究提供重要的数据支撑,用于前兆异常、同震响应、区域应力变化特征、含水层参数反演、观测机理等研究。地下流体井水位、水温数据集不仅可为地震预测预报和科学研究提供服务,而且在国民经济建设领域具有重要的应用价值。     

我国地震地下流体前兆台站现状的调查与分析

系统介绍了我国地震地下流体前兆台站的产权与管理权关系,观测点的井泉类型、观测井深度,观测层类型与地下水物理化学特征,观测项目及仪器类型与运行现状,井房及其供电与通讯条件,观测人员的学历与专业结构、年龄与工龄结构等,为“十五”台站优化与建设方案的制定提供依据。     

Geochemistry of the Springfield Plateau aquifer of the Ozark Plateaus Province in Arkansas,Kansas, Missouri and Oklahoma,USA

Geochemical data indicate that the Springfield Plateau aquifer, a carbonate aquifer of the Ozark Plateaus Province in central USA, has two distinct hydrochemical zones. Within each hydrochemical zone, water from springs is geochemically and isotopically different than water from wells. Geochemical data indicate that spring water generally interacts less with the surrounding rock and has a shorter residence time, probably as a result of flowing along discrete fractures and solution openings, than water from wells. Water type throughout most of the aquifer was calcium bicarbonate, indicating that carbonate‐rock dissolution is the primary geochemical process occurring in the aquifer. Concentrations of calcium, bicarbonate, dissolved oxygen and tritium indicate that most ground water in the aquifer recharged rapidly and is relatively young (less than 40 years). In general, field‐measured properties, concentrations of many chemical constituents, and calcite saturation indices were greater in samples from the northern part of the aquifer (hydrochemical zone A) than in samples from the southern part of the aquifer (hydrochemical zone B). Factors affecting differences in the geochemical composition of ground water between the two zones are difficult to identify, but could be related to differences in chert content and possibly primary porosity, solubility of the limestone, and amount and type of cementation between zone A than in zone B. In addition, specific conductance, pH, alkalinity, concentrations of many chemical constituents and calcite saturation indices were greater in samples from wells than in samples from springs in each hydrochemical zone. In contrast, concentrations of dissolved oxygen, nitrite plus nitrate, and chloride generally were greater in samples from springs than in samples from wells. Water from springs generally flows rapidly through large conduits with minimum water–rock interactions. Water from wells flow through small fractures, which restrict flow and increase water–rock interactions. As a result, springs tend to be more susceptible to surface contamination than wells. The results of this study have important implications for the geochemical and hydrogeological processes of similar carbonate aquifers in other geographical locations. Copyright © 2000 John Wiley & Sons, Ltd.     

井水位前驱波普遍性问题的探讨

Taking five underground water level observation wells with high earthquake response capability and located in Shanxi, Hebei and Inner Mongolia as study objects, this paper studies and discusses the gen...     

地下流体动态的观测环境干扰影响距离研究

根据我国地震地下流体动态干扰因素及其影响的调研结果,以井区水文地质条件分区,观测含水层性分类与渗透性分级为基础,研究了各类干扰源的影响距离,给出了干扰源与观测井间的最小距离即干扰源的最大影响距离,为地震台站观测环境保护提供了标准。     

Analysis of methods to estimate spring flows in a karst aquifer

Hydraulically and statistically based methods were analyzed to identify the most reliable method to predict spring flows in a karst aquifer. Measured water levels at nearby observation wells, measured spring pool altitudes, and the distance between observation wells and the spring pool were the parameters used to match measured spring flows. Measured spring flows at six Upper Floridan aquifer springs in central Florida were used to assess the reliability of these methods to predict spring flows. Hydraulically based methods involved the application of the Theis, Hantush-Jacob, and Darcy-Weisbach equations, whereas the statistically based methods were the multiple linear regressions and the technology of artificial neural networks (ANNs). Root mean square errors between measured and predicted spring flows using the Darcy-Weisbach method ranged between 5% and 15% of the measured flows, lower than the 7% to 27% range for the Theis or Hantush-Jacob methods. Flows at all springs were estimated to be turbulent based on the Reynolds number derived from the Darcy-Weisbach equation for conduit flow. The multiple linear regression and the Darcy-Weisbach methods had similar spring flow prediction capabilities. The ANNs provided the lowest residuals between measured and predicted spring flows, ranging from 1.6% to 5.3% of the measured flows. The model prediction efficiency criteria also indicated that the ANNs were the most accurate method predicting spring flows in a karst aquifer.     

Modelling tidal signals enhanced by a submarine spring in a coastal confined aquifer extending under the sea

Submarine springs discharge offshore groundwater from confined aquifers extending under the sea. The effects of these springs on the propagation of tidal oscillations in coastal confined aquifers are not known. This paper presents an approximate analytical solution of tidal head fluctuations in a confined aquifer with one submarine spring. The aquifer is assumed to extend in all directions infinitely. The spring is represented by a permeable round column on the seabed, which penetrates completely the impermeable layer overlying the confined aquifer. The error of the approximate solution is negligible if the distance from the spring to the coastline is much greater than the radius of the permeable column representing the spring. Through a hypothetical example, we demonstrate that it is possible to identify the spring’s location using tidal signals observed from inland wells. Tidal groundwater head fluctuations from three inland observation wells at least are needed to determine the 5 model parameters, including the location (2 parameters), the radius of the permeable column representing the spring, the diffusivity of the aquifer, and the tidal loading efficiency of the system.     

Sinkholes Due to Groundwater Withdrawal in Tazerbo Wellfield,SE Libya

The desert of eastern Libya forms one of the most arid regions of the Sahara. The Great Man‐Made River Project (GMRP) was established. It transports millions of cubic meters of water a day from desert wellfields to the coastal cities, where over 80% of the population lives. The Tazerbo Wellfield is one of the wellfields designed within the GMRP, delivering water to the eastern coast of Libya through an underground pipe network. Tazerbo Wellfield consists of 108 production wells; each well was designed to pump 100 L/s. The planned total groundwater withdrawal from all wells is 1 million m³/d. The deep sandstone aquifer (Nubian sandstone) is covered by a thick mudstone‐siltstone aquitard and is being heavily pumped. The aquifer and fine‐grained sediments of the aquitard may be compacted resulting in land subsidence as a result of high exploitation. Local sinkholes have developed in the area of Tazerbo since the start of the pumping from the wellfield in 2004. These sinkholes have been caused mainly by lowering of the piezometric heads due to the withdrawal of groundwater. In this study, a hydrogeological investigation is presented about the effect of large groundwater pumping from the Nubian sandstone aquifer in Tazerbo Wellfield, SE Libya, based on physical parameters for 108 production wells and 23 observation wells.