电磁干扰实验研究

本文分析了地电、地磁同台观测中出现的干扰问题，并针对地电观测对地磁场测量的影响进行了研究。通过实地测量和对长直导线产生的磁场模拟计算，得出不同距离（20～120m）的感应磁场强度值，由此判断通电导线对周围地磁场的影响。结果表明：电流为2A时，单根导线距地磁场观测点距离应大于150m；导线两侧在相等距离处对地磁总场的干扰并不遵循“数值相等，方向相反”的规律，而是一侧增加量大于另一侧减少量。这项实验研究为地磁、地电同台观测及排除干扰提供了有价值的依据。     

Magnetic Field Feedback Circuit for Geomagnetic Field Compensation Control

In the current state of geomagnetic instrument testing, some aspects of geomagnetic instrument performance are difficult to test in the laboratory. If laboratory test results are inadequate, the instrument will have multiple problems while operating in the field, where a geomagnetic instrumentation test platform with a stable natural magnetic field is critical. Here, the magnetic field feedback circuit for geomagnetic field compensation control is studied in detail. That is, the magnetic field measured by the feedback magnetic sensor and the required working magnetic field are compared as input to the system, and the electric signal is transmitted to the feedback coil through an analog circuit to form a closed loop control, which provides compensation to control the magnetic field. Compared with the existing magnetic shielding method, the analog control circuit can achieve the realization of any working magnetic field, and it is not limited to a null magnetic field. The experimental result shows that the system compensates the earth''s magnetic field of 10,000nT with an average error of 10.6nT and average compensation error of 0.106%, providing a high compensation accuracy. The system also shows high sensitivity and excellent stability. The feedback circuit has achieved effective compensation control for the earth''s magnetic field.     

观测场地漏电导致的地电场观测异常变化分析

通过对弥渡地震台地电场观测系统及观测环境相关项目进行逐项核实、分析,结合观测资料的异常变化特征,进行重点排除、查找,找到引起观测资料异常变化的原因是观测场地附近路灯线路漏电所致,判定该异常不是地震前兆异常。     

Field measurements of soil creep

An instrument has been designed to measure soil creep optically with a minimum of site disturbance. The instrument is sufficiently sensitive to detect movement in the soil over periods as short as one month. The results of measurements over a nine month period indicate that movement in the soil occurs in seemingly random directions and that large total movement does not necessarily imply a similarly large downslope movement. It is suggested that measurements of the type reported here are necessary for a satisfactory examination of the process involved in soil creep but that measurements over very long time periods are required for estimates of the rate of downslope transport.     

Field studies of rainsplash erosion

Studies on sandy soils of the Cottenham Series in mid-Bedfordshire confirm in the field the relationships between splash erosion, rainfall energy and ground slope obtained in the laboratory experiments of other workers. Only 0·06 per cent of the rainfall energy contributes to splash erosion and rates are low, attaining a maximum of 0·082 kg m^?2 y^?1 on a slope of 11°. The major role of splash action is in the detachment of soil particles prior to their removal by overland flow.     

GPS应变场云图方法识别地震形变场异常初步分析

介绍一种获取地震形变场异常的应变场云图方法.首先在指定时间窗内对GPS位移时间序列进行拟合速度值、插值速度场和计算应变场处理,然后以一定步长滑动得到时空连续的应变场动态变化图像,进而提取形变场异常信息.通过分析门源Ms6.4地震与震前应变场时空演化对应关系,说明本方法对预测地震有一定的指示作用.在2019年年终会商中,对嫩江ML4.5地震提出预测意见并检验了实用性.研究认为,应变场云图是一种有效、直观识别震前形变场异常的方法,可在地震会商工作中推广应用.     

鲁西重磁场异常变化特征的综合分析

从时间上和空间上系统地分析了山东西部及邻区流动重磁资料的变化特征,着重对鲁西测区地磁资料自2001年观测以来的变化特征详细地阐述,并与冀鲁豫交界地区重力资料进行了对比,结合地震活动关系进行探讨,发现鲁西重磁场具有显著的阶段性特征,这可能反映了地震不同孕育阶段的特征,为以后深入分析重磁场变化特征的相关性及变化机理研究奠定基础。     

Use of Computers in the Field

Performing long-term pump tests, single-well aquifer tests and long-term ground water monitoring were, in the past, considered costly and labor-intensive tasks. However, because of recent advances in portable data acquisition systems, these field tests can be performed in a relatively cost-effective and efficient manner. Certain data acquisition systems (DAS) have unique options available. Recently developed and commonly used computers are the Envirolab®, the Paroscientific®, and the In-Situ®. The use of implementing DAS in ground water field studies has proved to be successful when compared to the many disadvantages of performing those tasks manually. Successful acquisition of aquifer characterization data using computerized methods is highly dependent on the implementation of proper field programming and operational procedures. In order to provide high qualify and meaningful data, the field operator must be familiar with proper equipment implementation and programming instructions. Once familiar with these procedures, the use of DAS in the field provides a cost-effective and efficient tool for aquifer testing.     

大地电场日变化特征

利用后土桥等地震台的大地电场分钟值资料,分析了各方向的日变形态和特征。结果发现,一般各方向日变与地磁场日变近似,出现双峰单谷。而后土桥地震台有别于其他地震台,东西向以半日波为主,出现双峰双谷。     

Field Evaluation of Well Purging Procedures

In order to avoid contamination of ground water samples by stagnant water in the well bore, it is generally recommended that the well be purged prior to sampling. There is however, a divergence of opinion both on the need for purging and the best methods of purging. This paper describes detailed field tests in which non-reactive tracers were used to examine, from a well hydraulics point of view, the need for purging and also the effectiveness of various purging procedures. Results show that in the permeable geologic materials of the test site, and for the non-reactive tracers, the water within the screened interval will be purged by the natural flow of water through the screen, while the water above will remain stagnant. The volume of water above the screen is referred to here as one bore volume. It,is suggested that with consideration of the required sample volume, the volume of water stored in the screen, the sampling rate, and the position of the sampler intake, dedicated samplers could be used to obtain representative ground water samples without prior purging of the well.
Of the purging procedures tested, pumping from just below the air-water interface in the well, or the method of "complete removal" of the water within the well bore were the only effective means for complete removal of the stagnant water. Using these procedures, it appeared that representative samples could be obtained with the removal of only two to three bore volumes of water.     

地震活动的随机场特征

地震活动是一种随机自然现象,将其基本要素变量看作是空间和时间的函数,它们具有随机场的基本特征,由此得到地震活动的随机场描述。重点讨论在一定条件下地震活动能量场和频次场的统计特征及地震活动场的平稳性问题,说明应用随机场方法研究地震活动的合理性。     

Field observations of nearshore bar formation

The formation of an inner nearshore bar was observed during a high‐energy event at the sandy beach of Vejers, Denmark. The bar accreted in situ during surf zone conditions and the growth of the bar was associated with the development of a trough landward of the bar. Measurements of hydrodynamics and sediment fluxes were obtained from electromagnetic current meters and optical backscatter sensors. These process measurements showed that a divergence in sediment transport occurred at the location of the developing trough, and observed gradients in cross‐shore net sediment flux were consistent with the morphological development. The main cause for the flux gradients were cross‐shore gradients in offshore‐directed mean current (undertow) speed which depended upon local relative wave height and local bed slope. Copyright © 2007 John Wiley & Sons, Ltd.     

地磁场模型研究

国际地磁参考场与局部地磁场模型的研究，具有深远的学科意义与巨大的实用价值，研究好地磁场模型，将可以提供准确的地磁场信息，丰富“数字地球”的数字化与可视化的程度。     

关于流场法理论的几点认识

基于长期从事水工建筑物渗漏、管涌等安全隐患检测工作的需要,结合水工建筑物渗漏管涌隐患分布的特点,对水底及水体中的电场分布进行了分析研究.本文从水流场与电流场的相似性、渗流场与电流场的相似性以及动态导体充电法的相关理论三个方面阐述了流场法理论的客观性、合理性以及与动态导体充电法理论的兼容性.首先利用水流场与电流场的相似性解释异常水流场,其次从渗流场与电流场的相似性解释异常水流场,最后利用水工建筑物堤坝渗漏管涌通道地电模型,进一步论述了利用地下动态导体充电法中的不等位导体理论来认识流场法理论更为方便,并可以进行渗漏出口处的电流强度计算及进行正反演计算,同时证明了异常水流场与电流场有着近似的对应关系,以工程实例介绍了流场法在水工建筑物渗漏管涌检测中的应用.     

双探针式星载电场测量仪

该文在概述双探针式、天线式和电子漂移式三种星载电场测量仪的基础上,重点论述了适合于地震电磁探测试验卫星的双探针式星载电场测量仪.对双探针式星载电场测量仪的工作原理,电场测量仪探头、卫星平台与等离子体之间的相互作用,电场测量仪的标定方法及其星上和地面数据处理方法等进行了论述.     

GOCE Gravity Field Processing Strategy

A processing strategy and the corresponding software architecture for the processing of GOCE (Gravity field and steady-state Ocean Circulation Explorer) observables is presented and described, with the major objective to compute a high-accuracy, high-resolution spherical harmonic model of the Earth's gravity field. The combination of two numerical solution strategies, i.e. the rigorous solution of the corresponding large normal equation systems applying parallel processing (on a PC cluster) as the core solver, and the fast semianalytic approach as a quick-look gravity field analysis (QL-GFA) tool, is proposed. Such a method fusion benefits from the advantages of the individual components: the rigorous inversion of the system providing also the full variance-covariance information, and the quickness enabling the consecutive production of intermediate gravity field solutions, for the purpose to analyse partial and incomplete data sets and to derive a diagnosis of the performance of the GOCE measurement system. The functionality and operability of the individual components are demonstrated in the framework of a closed loop simulation, which is based on a realistic mission scenario both in terms of the orbit configuration and the coloured measuring noise. Special concern is given to the accuracy of the recovered coefficients, the numerical behaviour, the required computing time, and the particular role of the individual modules within the processing chain. In the case of the core solver, it is demonstrated that the assembling and rigorous solution of large normal equation systems can be handled by using Beowulf clusters within a reasonable computing time. The application of the quick-look tool to partial data sets with short-term data gaps is demonstrated on the basis of several case studies. Additionally, the spectral analysis of the residuals of the adjustment is presented as a valuable tool for the verification of the noise characteristics of the GOCE gradiometer.     

中国大陆应变应力场研究

根据1999～2009年网络工程GPS观测资料计算得到的应变率参数,研究了中国大陆地壳的应变应力场及其地壳现今的水平活动特征。结果表明,中国大陆地壳西部青藏亚板块的压应力主方向围绕藏南和阿萨姆构造结向北、东、南依次辐射撒开。新疆亚板块自西向东由近SN向变为NE向。中国大陆东部地壳的压应力主方向自北向南由NEE变为近EW向,再变为SEE向。中国大陆主压应力作用强度西部显著大于东部。中国大陆地壳西部强于东部,南部强于北部,现今西部地壳以挤压、走滑为主,东部地壳既有挤压、走滑,也有拉张。     

福建地区速度场特征

利用2005-2009年福建GPS基准站资料.解算了各测站20期的季速度场,结合近年福建及其周边大地震,分析了福建地区速度场变化特征.结果表明,2007年南海地震发生时段,福建各测站的速度场发生明显变化,反映了福建地区速度场受菲律宾板块运动的影响.