磁变仪标度值自动测量装置

1.概述过去佘山台地磁组测量磁变仪标度值一直是用手动方式进行的。控制开关包括正常仪和备用仪的共有7组,必须人为设定时间间隔按程序反复多次启闭才能完成测量工作既繁琐又易出差错。     

三分向磁变仪标度值自动测定电路

利用手工方法对磁变仪H、D和Z这3个分向进行标度值测定,从开机到工作结束大约需要20多分钟时间,加之测定期间需要进行电流调整、时间限定、电流换向等繁琐操作,使整个过程既耗时间又费精力。为改变这种现状,笔者设计组装了一种标度值自动测定仪,经台站使用,收到了良好效果。 1 主要性能和特点 (1)标度值电流和控制时间稳定。环境温度在0～30 ℃范围内变化时,电流基本不需要调整,测定时间误差小于1%。 (2)H、D、Z分向的标度值电流和测定时间可在一定范围内连续可调,方便实用。 (3)操作简单。在进行标度值测定时,只需按动一下启动开关,即…     

介绍一种磁秤标度值自动测定电路

为了使用磁秤标度值测定的仪器操作更加方便，设计了一种标度值自动测定电路。介绍了电路的组成、工作原理和安装调试方法。     

红山地磁台的标度值问题

一、前言水平分量、磁偏角和垂直分量的磁变仪通常安装在同一个墩子上,并用同一个记录器把三者的光点记录在同一张磁照图上(图1)。为了防止磁针之间互相影响,三者之间距离一般约大于50cm。在测量标度值时,也要把三者标度值线圈的电路分开,独立地测量各个标度值,否则当电流同时通过3个线圈时,各自所产生的电流磁场就同时作用在3个仪器的磁针上,以致使得所测标度值不准确。其后果     

磁变仪布局的研究

本文提出了改进磁变仪布局的必要性和布局标准,对磁变仪定向及其稳定性、标度值稳定性和分量仪间允许的最小间距进行了研究,提出了可以提高磁变仪记录质量的改进布局和满足布局全部标准的新布局,改进布局特别是新布局可以显著提高磁变仪保持定向、抗干扰能力,获得记录标度值稳定的较理想的磁照图。     

减小水平分量磁变仪记录非线性的技术措施

讨论了减小水平分量磁变仪记录非线性的技术措施。选择适宜的标度值(C/M)、选取适当的入射角α_0、选择适当的记录距离R是改善水平分量磁变仪记录状态的主要途径。文中对比作了具体分析。     

水平分量磁变仪标度值随记录n变化率的测定及应用

水平分量磁变仪标度值Ｓ随记录ｎ的变化呈稳定的线性关系，但变化率Ｋｎ各地磁台仪器并不相同。用本文方法测定Ｋｎ可以获得满意的结果。Ｋｎ的精确测定可使水平分量磁变仪非线性记录的计算方法进入实用化，可以校正Ｋ尺或电磁转换函计算值使之更精确，从而提高地磁资料质量。     

水平分量磁变仪基线值漂移的初探

对水平分量磁变仪基线值负漂移现象作了探讨，认为地磁场水平强度的变化和水晶丝扭力系数的减小是影响水平分量磁变仪θ角改变的主要原因，也是影响定向改变的主要原因。另外，还对减小Ｈ仪基线负漂移的可能途径进行了讨论。     

三分量磁变仪自动标定器研制

大连地磁台三分量地磁仪原配用 CB-3型磁变仪配电盘用以提供记录灯电流 ,标定电流及三分量转换开关 ,随着磁照图质量越来越高 ,对标定电流的稳定性 ,电流的升降特性要求也越来越苛刻 ,原 CB-3型磁变仪配电盘很难适应 ,鉴于地磁全面化改造还有待时日 ,即使改造后可能仍需平行观测一个时期 ,应地震台的要求设计制作了这种三分量地磁仪自动标定电源。1　主要性能指标提供可调记录灯电流 80～ 1 3 0 m A;记录灯断丝报警 ;自动时号 ,曝光量连续可调 ,时号指示 ;定时触发标定 ;三分量标定过程自动完成 ;标定节拍连续可调 ;标定电流升降斜率由节…     

磁偏角磁变仪的定向

分析了影响磁偏角磁变仪定向质量的原因，指出应重视阻尼器影响，提出磁偏角磁变仪以在实际工作环境中定向最佳，用扭头带动镜面法定向实用性强，无须做任何改正。     

关于垂直分量磁变仪的灵敏度问题

目前国内地磁台垂直分量磁变以的灵敏度都普遍偏低，不能适应一些研究工作的需要，必须予以适当的提高，本文在基本不改变仪器固有灵敏度的前提下，采取记录光线二次反射法，以提高仪器的记录灵敏度，利用这种方法既使仪器的灵敏度提高一倍同时又保证了仪器原有的稳定性。     

兰州台地磁Z日变化"低点位移"与地震关系的分析研究

首先对兰州地磁台的基本情况进行了简要叙述，利用该台1974年1月-2002年7月的地磁Z日变化“低点位移”观测结果。对甘肃及邻区在相同时段内发生的Ms≥5.0以上的地震进行统计分析，探讨其震磁关系，以及映震效果在空间上的分布特征。为地震的短临预报提供一定的参考依据。     

Mapping of magnetic basement in Central India from aeromagnetic data for scaling geology

The Central Indian region has a complex geology covering the Godavari Graben, the Bastar Craton (including the Chhattisgarh Basin), the Eastern Ghat Mobile Belt, the Mahanadi Graben and some part of the Deccan Trap, the northern Singhbhum Orogen and the eastern Dharwar Craton. The region is well covered by reconnaissance‐scale aeromagnetic data, analysed for the estimation of basement and shallow anomalous magnetic sources depth using scaling spectral method. The shallow magnetic anomalies are found to vary from 1 to 3 km, whereas magnetic basement depth values are found to vary from 2 to 7 km. The shallowest basement depth of 2 km corresponds to the Kanker granites, a part of the Bastar Craton, whereas the deepest basement depth of 7 km is for the Godavari Basin and the southeastern part of the Eastern Ghat Mobile Belt near the Parvatipuram Bobbili fault. The estimated basement depth values correlate well with the values found from earlier geophysical studies. The earlier geophysical studies are limited to few tectonic units, whereas our estimation provides detailed magnetic basement mapping in the region. The magnetic basement and shallow depth values in the region indicate complex tectonic, heterogeneity, and intrusive bodies at different depths, which can be attributed to different thermo‐tectonic processes since Precambrian.     

Evaluation of bias on the probability of collapse from amplitude scaling using spectral-shape-matched records

Although for many years it was thought that amplitude scaling of acceleration time series to reach a target intensity did not introduce any bias in the results of nonlinear response history analyses, recent studies have showed that scaling can lead to an overestimation of deformation demands with increasing scale factors. Some studies have suggested that the bias can be explained by differences in spectral shape between the response spectra of unscaled and scaled records. On the basis of these studies, some record selection procedures assume that if records are selected using spectral-shape-matching procedures, amplitude scaling does not induce any bias on the structural response. This study evaluates if bias is introduced on lateral displacement demands and seismic collapse risk estimates even when spectral shape is carefully taken into consideration when selecting ground motions. Several single-degree-of-freedom and multiple-degree-of-freedom systems are analyzed when subjected to unscaled and scaled ground motions selected to approximately match the mean and the variance of the conditional spectrum at the target level of intensity. Results show that an explicit consideration of spectral shape is not enough to avoid a systematic overestimation of lateral displacement demands and collapse probabilities as the scale factor increases. Moreover, the bias is observed in practically all cases for systems with strength degradation and it increases with decreasing period and decreasing lateral strength relative to the strength required to remain elastic. Key reasons behind the bias are presented by evaluating input energy, causal parameters, and damaging pulse distributions in unscaled and scaled ground motion sets.     

导致拾震器常数标定进入误区的研究

在拾震器的标定过程中，当Ri≤10MΩ时，空气阻尼太大，所测定的D10结果不准确，从而导致S1、a12、RD以及C、β12均不准确，所得V也不准确，同时记录地震的波形也会受到影响，为此建议在标定和工作时，要串上分压电阻R，以此为导向使得放大器输入电阻Ri≥10MΩ时，所得结果才能符合规范要求，本研究通过多次测试均达到良好的效果。     

The effect of amplitude scaling limits on conditional spectrum-based ground motion selection

Amplitude scaling is commonly used to select ground motions matching a target response spectrum. In this paper, the effect of scaling limits on ground motion selection, based on the conditional spectrum framework, is investigated. Target spectra are computed for four probabilistic seismic hazard cases in Western United States, and 16 ground motion suites are selected using different scaling limits (ie, 2, 5, 10, and 15). Comparison of spectral acceleration distributions of the selected ground motion suites demonstrates that the use of a scaling limit of 2 yields a relatively poor representation of the target spectra, because of the small limit leading to an insufficient number of available ground motions. It is also shown that increasing scaling limit results in selected ground motions with generally increased distributions of Arias intensity and significant duration Ds_5-75, implying that scaling limit consideration can significantly influence the cumulative and duration characteristics of selected ground motions. The ground motion suites selected are then used as input for slope displacement and structural dynamic analyses. Comparative results demonstrate that the consideration of scaling limits in ground motion selection has a notable influence on the distribution of the engineering demand parameters calculated (ie, slope displacement and interstory drift ratio). Finally, based on extensive analyses, a scaling limit range of 3 to 5 is recommended for general use when selecting ground motion records from the NGA-West2 database.