用于地电阻率交流电法观测的低频稳流电源研发

为了解决地电阻率观测中台站受环境干扰而影响观测等问题,我国地震工作者正在研究和尝试基于交流电法的新型地电阻率观测系统,这种新型观测系统主要由低频稳流电源系统和接收系统组成。本文对低频稳流电源系统的关键技术进行了分析,并介绍了电源系统的功率变换电路和逆变输出电路等关键环节设计,最后对研发的具有大功率可变频稳流输出性能的低频电源样机的输出性能进行了测试。测试结果表明,该型电源样机的各项技术指标均达到了设计要求,其输出性能良好。     

聊古1井在不同取水模式下气体观测效果的对比分析

为解决聊古1井断流问题,聊城地震水化试验站先后引进、开发了人工激发引流观测技术和潜水泵变频稳流抽水技术.对天然自流观测系统、人工激发引流观测系统和潜水泵变频稳流抽水观测系统等3种不同取水模式下产出的气体观测数据进行一致性分析.结果表明,人工激发引流观测系统下气体观测动态特征年变比较明显,潜水泵变频稳流抽水观测系统下气体观测动态特征与天然自流状态下的动态特征基本一致.     

地电阻率观测系统稳流电源技术的发展

详尽地分析了地电阻率观测系统的供电电源的发展过程。对几种电源的技术指标和性能作出了评价。在对几种电源的若干技术问题进行了分析和讨论后，指出对地电阻率观测系统的稳流电源的设计应用高频开关电源技术。介绍了作设计的主电路图。     

阳原地震台的改造建设--地电阻率观测中的干扰及排除

阳原台地电阻率观测受外界影响非常严重，因而严重影响了观测资料的精度，使资料质量大大降低。本文通过实验和研究，找到了影响资料观测精度的因素：(1)漏电；(2)电极老化；(3)稳流源输出不稳定；(4)降雨；(5)风扰，并分别加以排除。     

基于逆重复m序列的岩矿石标本电性参数测量方法研究

岩矿石标本电性参数实验中,常使用一个或者多个频率激励的变频法测量电阻率,存在观测效率低、可用信息少、抗干扰能力弱等实际问题.本文将变频法改进为伪随机电流信号法进行观测,提出激励场源使用逆重复m序列伪随机电流信号的观测方法,推导出抑制工频干扰的参数选取条件,进而针对岩矿石标本电性参数实验中激励场源的特殊要求,详细分析了观测系统中信号产生与接收面临的问题,并给出了解决方法:采用高驱动能力设计及阻抗匹配技术解决岩矿石标本电阻率分布跨度大(n×10ⁿ×10⁶Ωm)导致的发送端驱动能力不足以及接收端阻抗不匹配等问题;采用系统频率响应校正技术修正系统存在的观测误差;采用高频微弱信号产生与拾取的相关技术,保证电流密度处于岩矿石标本的线性响应区间,避免非线性效应,实现宽频率分布范围观测(10-3~10⁴kHz).采用所研发的可编码、高精度、小电流(10^-6A)、连续可调输出的精密电流源,使用阻容模型进行实验测试,结果表明:(1)该方法可在10^-3~10⁴Hz频带内产生90个有效测量频点,可满足频带宽、频点密、压制工频干扰的观测要求;(2)实验中恒流源输出稳定,不同负载下直流输出稳定性误差小于0.5%,精度满足实验中对输出电流的要求;(3)标定后测量误差小于0.5%,系统具有较高的观测精度与抗干扰能力;(4)与变频法相比观测效率提高2.3倍.通过该方法开发的观测装置可有效提高工作效率和抗干扰能力,提高观测数据的准确性,适用于各种类型岩矿石标本电性参数观测工作.     

补偿电流对核旋分量仪的影响及补偿稳流装置

着重讨论补偿电流对核旋分量磁力仪在观测地磁场垂直分量中的影响,介绍了补偿稳流装置和在大连地磁台应用的效果。     

编码源地电阻率观测试验

地电阻率的高精度观测是实现地震预测预报的前提之一.面对日益严重的电磁干扰,提出了基于编码源循环互相关辨识技术的地电阻率观测方法,其实质是将待测地质体视为待辨识系统,利用编码源信号激励供电电极A和B产生的电流信号作为系统输入信号,测量电极M与N之间的电压信号作为系统响应输出,将输入和输出信号严格同步采样为时间序列,分别与参考信号进行循环互相关运算并转换至频率域计算获得待探测地电阻率谱(幅度和相位).由于系统环境的干扰和随机噪声与编码源信号不相关,通过循环互相关运算可以达到抑制环境随机噪声和干扰的目的.这种地电阻率观测体系在环境干扰较大的甘肃省兰州观象台和陇南汉王地震台站利用现有的观测场地和线路进行了观测试验,测量结果显示,数据的一致性好、均方差小,说明该方法在强干扰环境下具有较好的抗电磁干扰能力,观测频带较以往直流电法测量有较大的扩展.该方法为现有地面地电阻率台站持续发展提供了技术保障,可为地震预报与科学研究提供高质量的地电阻率观测数据.      

基于SPWM技术的大功率稳流电源

为了解决地电阻率台站饱受环境干扰等问题,中国地震科技工作者致力于研究基于交流电法的新型电阻率观测系统,该系统主要由交流稳流电源和接收机组成。介绍电源研制过程涉及的SPWM驱动信号实现方法、高频变压器的设计方法等关键技术,并对电源样机进行输出性能测试。测试结果表明,电源样机的各项技术指标均达到设计要求,具有良好的输出性能。     

潜水泵变频稳流抽水观测技术系统

潜水泵变频稳流抽水观测技术系统适用于不同观测条件,可以保证原有水文地球化学各测项的数字化和模拟观测,还可实施数字化水位与水温的同井观测,可以记录清晰的潮汐效应和同震效应,不低干天然自流状态下观测资料质量水平,是值得推广的新技术.     

WL3型稳流电源

一、前言我国现行的地电阻率观测方法,采用的是中常大小极距的四极对称法。测量仪器多使用DDC—2A电子自动补偿仪。供电方式大致可分:1.整流供电,供电时将供电电流调到某一固定值上,测人工电位时,若电网电压,负载电阻发生变化,均会引起供电电流的变化,致使地电阻率观测误差大;2.稳压供电,对供电电流值要进行测量,也会引入误差;3.稳流     

Electrical Imaging of Impact Structures

Electrical imaging provides important subsurface information for the construction of hypervelocity impact models. We here provide an overview and evaluation of the current electrical imaging methods used in impact cratering studies. Although apparent resistivity models are commonly used in the geoelectrical imaging of impact structures, the reliability of these models has not hitherto been determined. In order to assess these imaging approaches in impact cratering, we investigate for the first time the discrepancies between the apparent resistivity and true resistivity models of an impact structure. To this end, we present (1) a new true resistivity model of the Araguainha impact structure in central Brazil by applying L2-norm inversion to previously published data, (2) apparent resistivity model of the impact structure, and (3) models obtained from different stages of the iterative tomographic inversions. Our results show that changes in vertical resistivity gradient are significantly better defined in the true resistivity models than in the apparent resistivity model. On the basis of these results, we outline a new approach that true resistivity models can be effectively assessed by applying both L1- and L2-norm inversion schemes together with the monitoring of intermediate models from iterative inversion. The results of our study highlight the importance of tomographic inversion of resistivity data in impact cratering studies, and they provide a data modeling framework and foundation for cost-effective subsurface imaging of impact structures in the future.     

TRANSFORMATION OF RESISTIVITY SOUNDING MEASUREMENTS OBTAINED IN ONE ELECTRODE CONFIGURATION TO ANOTHER CONFIGURATION BY MEANS OF DIGITAL LINEAR FILTERING*

The technique of digital linear filtering is used for transformation of apparent resistivity data from one electrode configuration into another. Usually filter spectra are determined via the discrete Fourier transforms of input and output functions: the filter characteristic is the quotient of the spectra of the output function and input function. In this paper, the transformation of the apparent resistivities is presented for four electrode configurations (Wenner, the two-electrode, Schlumberger, and dipole configurations). In our method, there is no need to use the discrete Fourier transform of the input and output functions in order to determine the filter spectrum for converting apparent resistivity in one electrode configuration to any other configuration. Sine responses for determination of the derivative of apparent resistivities are given in analytical form. If the filter spectrum for converting the apparent resistivity to the resistivity transform for one electrode configuration is known, the filter spectra for transforming the apparent resistivity to the resistivity transform for any electrode configurations can be calculated by using newly derived expressions.     

多极距地电阻率观测系统的分布式电极控制器研制

详述数字电极的系统构成、电路结构、通信协议和其他关键技术。该系统的通信网络结构基于RS-485现场总线,通过环境测试和台站试验,发现数字电极技术适用于多极距电阻率系统。     

任意各向异性介质中三维可控源音频大地电磁正演模拟

在一些地层层理发育的地区,地下介质存在显著的电各向异性,此时基于各向同性模型解释含各向异性效应的可控源音频大地电磁（CSAMT）测深观测数据会导致错误的结果.本文通过引入3×3的对称正定张量表征电导率各向异性,采用非结构四面体网格和矢量有限元方法离散电场满足的矢量Helmholtz方程,并将电磁场源等效为系列电偶极子,实现任意各向异性介质中CSAMT高效数值模拟.本文首先通过层状各向异性模型检验三维有限元算法的精度和有效性,进一步建立三维地电模型研究异常体各向异性和围岩各向异性对CSAMT响应的影响,最后使用视电阻率极性图来识别各向异性电导率主轴方向.数值模拟结果表明,各向异性电导率对CSAMT视电阻率幅值及分布规律都有很大影响,视电阻率极性图能够很好地识别各向异性主轴方向.     

电偶源频率电磁测深中的静位移现象及视电阻率曲线的畸变

以电偶源频率电磁测深 (FEMS)二维数字模拟为例 ,从理论上简略讨论了波区定义的 5种视电阻率的变化特征及静位移现象 ,定性分析了表面局部水平非均匀体对视电阻率曲线畸变的影响 .     

电测井中电流参数对地层的分辨能力分析

常规电测井一般通过测量供电电极的电流和测量电极之间的电位差来计算围岩的视电阻率并划分地层界面,而忽略了对电流参数的利用。本文基于欧姆定律,通过供电电极电流的变化定性分析其周围岩矿石电阻的变化,进而用电流强度变化曲线识别地层属性。理论分析和试验结果表明,供电电极电流大小取决于电极的接触电阻,而视电阻率大小取决两个测量电极之间或供电与测量电极之间介质的电阻率总和,因此,电流比视电阻率对地层的灵敏度要高一些。绘制电流强度测井曲线可以准确划分地层层位,确定地层厚度,且不增加成本。     

An assessment of inversion methods for AEM data applied to environmental studies

Airborne electromagnetic (AEM) surveys are currently being flown over populated areas and applied to detailed problems using high flight line densities. Interpretation information is supplied through a model of the subsurface resistivity distribution. Theoretical and survey data are used here to study the character and reliability of such models. Although the survey data were obtained using a fixed-wing system, the corresponding associations with helicopter, towed-bird systems are discussed. Both Fraser half-space and 1D inversion techniques are considered in relation to their ability to distinguish geological, cultural and environmental influences on the survey data. Fraser half-space modelling provides the dual interpretation parameters of apparent resistivity and apparent depth at each operational frequency. The apparent resistivity was found to be a remarkably stable parameter and appears robust to the presence of a variety of at-surface cultural features. Such features provide both incorrect altitude data and multidimensional influences. Their influences are observed most strongly in the joint estimate of apparent depth and this accounts for the stability of the apparent resistivity. Positive apparent depths, in the example data, result from underestimated altitude measurements. It is demonstrated that increasingly negative apparent depths are associated with increasing misfits between a 1D model and the data. Centroid depth calculations, which are a transform of the Fraser half-space parameters, provide an example of the detection of non-1D influences on data obtained above a populated area. 1D inversion of both theoretical and survey data is examined. The simplest use of the 1D inversion method is in providing an estimate of a half-space resistivity. This can be undertaken prior to multilayer inversion as an initial assessment. Underestimated altitude measurements also enter the problem and, in keeping with the Fraser pseudo-layer concept, an at-surface highly resistive layer of variable thickness can be usefully introduced as a constrained parameter. It is clearly difficult to ascribe levels of significance to a ‘measure’ of misfit contained in a negative apparent depth with the dimensions of metres. The reliability of 1D models is better assessed using a formal misfit parameter. With the misfit parameter in place, the example data suggest that the 1D inversion methods provide reliable apparent resistivity values with a higher resolution than the equivalent information from the Fraser half-space estimates.