地震仪的反馈阻尼

英国Sensonics公司生产的DTR—700型磁带记录地震仪与我国通用的电子放大地震仪器相比有一个不同点,就是拾震器的阻尼是由放大器对拾震器的反馈电流所提供的,即拾震器具有所谓“反馈阻尼”(Feedback Damping)。具有反馈阻尼的拾震器,其阻尼的调节不是象一般地震仪那样,通过改变拾震器和放大器之间网络电阻的阻值来进行,而是通过反馈电流大小的控制来进行。这种接法的好处是最大限度地利用了换能器的输出(因为没有信号消耗在阻尼匹配网络电阻上),增加了换能器的工作稳定性。过去我们的地震仪     

北京台网拾震器电压灵敏度标定解析

北京台网拾震器电压灵敏度标定解析范涛（中国北京１０００８１国家地震局地球物理研究所）拾震器的输出电压灵敏度Ｓ＿（１２）是地震仪器的主要基本参数之一，它直接影响观测系统放大率的准确性，进而影响数据处理的精度。近几年来，北京台网对安装在地面上的转动型拾震...     

测震学（一）

测震学是一门有关地震地面运动的侦查与测量的技术学科。它包括地震仪的设计、标定、安装以及根据地面运动对地震图的定量解释。一套地震仪由一个或几个拾震器、一个时钟或时间信号接收器和记录器组成。本章集中在拾震器的理论和使用方面。对设计技术不作详细描述，但要谈到一些一般性设计原理。     

用激励标定线圈的方法测定地震计的阻尼常数D_1

对于电子放大的短周期地震仪系统,为了确定拾震器阻尼常数D_1,一般是通过实验测定磁电式换能器下列参数之一,即: 换能器的电流常数P 换能器的电动常数G     

微震仪拾震器的组配使用

灵活、熟练地掌握DS—1型、64型、65型、维开克型拾震器在地震仪系统中的组配(?)用,在震情监测工作中有重要意义,常常能有效地解决因仪器意外故障而造成的测震断记问题.本文介绍的“D73”微震仪系统,便是一种组配运用的形式.组配后,如何通过调整仪器参数达到标定值,是仪器使用的前提,实验结果说明,该系统可作为常规观测手段运用.     

温度对DD—1微震仪的影响

本文就发现常熟地震台 DD-1型短周期地震仪脉冲监视标定记录波形振幅的变化,与工作环境温度变化有较好的对应关系,对监视标定器本身、对地震仪拾震器、放大器及记录笔头受温度影响情况进行了理论分析、探讨,并对拾震器、放大器、记录笔头进行了温度试验等.此外还对使用自动标定器 DD-1仪器整机一次标定法标定,计算一年3次标定的仪器放大倍率与温度变化有直接关系,并给出了具体随温度变化的数据等.     

传递系数β12对全放大倍率的影响

通过对测震短周期拾震器的工作原理和微分标定原理及相关公式的分析,针对部分台站所使用的 Ｄ Ｓ－ １ 拾震器垂直摆磁缸退磁较严重,其中肯电阻低于设计值,仪器系统全放大倍率不能满足有关要求的问题,提出可利用拾震器闲置线圈 Ｒｓ１１ 提供阻尼,改变拾震器垂直摆偶合方式,提高传递系数β１２ ,从而达到提高全放大倍率的目的。     

拾震器输出电压灵敏度的简便测量方法

拾震器(摆)本身是台很精密的传感器,常期工作在野外地震台站上.受自然环境的影响和仪器本身的老化使仪器输出发生变化.直接影响地震信息的质量.依中国地震局遥测地震台网观测技术规范的要求,遥测台网子台所用拾震器输出电压灵敏度每两年测量一次.目前遥测地震台用的拾震器有两类:转动型拾震器如768中长周期型、DS-1型、DK-1型.直线型拾震器如768短周期型.介绍北京遥测台网关于这两类拾震器输出电压灵敏度的简便测量和计算方法.     

拾震器周期测定器

目前测定拾震器周期一般采用停表,直接目测拾震器幅动或通过记录器目测笔尖运动(或光点运动)来测量,这样精度较低,且费时费力,尤其是长周期拾震器的周期测量更是如此。为此我们试制了一个拾震器周期测定器如图1。拾震器→放大器→触发整形→计数器→电子秒表图1.拾震器周期测定器示意图     

DBX_(-1)型地震仪报警系统

地震仪的报警器大都安装在U—D向放大器的输出端.这存在两个问题:1.因报警器在U—D向上接着,当水平向放大器或拾震器出现故障引起记录笔尖大幅度摆动时,报警器不能发出警报;2.如果U—D向放大器或拾震器出现故障(指拾震器卡缸,放大器无输出或输出很小),在     

Developments in electromagnetic and hybrid seismometers

The “Willmore Mark II” variable-period electromagnetic seismometer has now been replaced by the Mark III/IIIA seismometers, which give a similar range of period and similar voltage output from a smaller and lighter package. The new instruments also offer facilities for calibration, for damping, and for the control of period over a wide range by the injection of appropriate signals into auxiliary coils. The Mark IIIA seismometer has been further adapted by the addition of a displacement transducer system, which enables it to operate as a force-balance accelerometer. A new “Mark IV” instrument is the prototype of a package which will contain three “sawn-off” seismometers derived from the Mark III with the additional displacement transducer, all designed to fit into a cylindrical pressure case for use as a three-component borehole instrument.The paper includes a circuit for displaying four different outputs from a short-period seismometer, with options for displacement and acceleration feedback, as Lissajous figures against an input which simulates sinusoidal acceleration in the earth.     

用函数变换设计速度传感反馈地震计

短周期地震计主要用于观测地方性的微小地震,用速度传感器设计的反馈式短周期的地震计的工作参数稳定性不好,是国内外观测实践都证实了的问题。借鉴位移传感反馈地震计工作参数偏差较低的思路,介绍了通过采用函数变换方法设计速度传感反馈地震计的解决方案。用函数变换方法设计的速度传感反馈地震计,既实现了加大负反馈深度又不降低噪声指标的双重目标,有加深负反馈和由闭环反馈生成的闭环周期位于通带外的优点。即便是机械摆受到环境变化的影响或随时间推移而出现了漂移或老化,其对通带内的幅频特性的影响亦较小。由函数变换电路生成摆函数的工作周期及工作阻尼与机械摆的参数完全无关,仅取决于变换电路中的两个电阻和两个电容的精度。     

RSDA-1型24位水库地震数据采集器的标定系统

RSDA-1型24位水库地震数据采集器中标定系统是测定地震计和参数的关键工具,是评判台站每天工作状态是否正常的评判手段,是标定系统特性的必须环节.根据地震计和台站不同需要,需在采集器中设计4种标定信号,即脉冲标定、正弦标定、伪随机信号和高阶脉冲信号.本文主要介绍标定系统及4种标定信号在24位地震数据采集器中的设计和实现.     

地震台阵流动地震仪的检测与标定方法研究

流动地震仪组成的台阵观测系统已经成为地下结构、物性探测的基本工具,高质量观测数据的获取是以地震仪的性能为基础的。本文结合中国地震科学探测台阵系统建设与维护实践,介绍了科学探测台阵系统采用的几项检测标定技术,包括超低频振动台标定、仪器一致性组网检测、白噪声标定和现场快速仪器检测,形成了一套适合地震流动台阵仪器的检测标定方法,并在观测实践中获得较好的应用。     

宁夏陶乐井下地震计的参数测定

宁夏回族自治区数字化测震台网由14个数字化测震台站构成,其中宁夏灵武和宁夏陶乐为井下式数字化测震台站。宁夏陶乐数字化观测井此前使用JDF-2型号地震计,但由于仪器老化导致记录波形失真,经研究决定,于2018年12月底将宁夏陶乐观测井的地震计及数据采集器更换为井下短周期GL-S2B型号地震计、EDAS-24GN型号数采。在北京港震仪器设备有限公司技术人员的配合下,宁夏测震台网工作人员对更换后的井下短周期GL-S2B型号地震计、EDAS-24GN型号数据采集器进行了方位角校正、阶跃标定、正弦标定、台基噪声功率谱密度测试等参数测定,各项测定结果均符合井下地震计及数采的安装规范,且记录波形良好。     

速度传感反馈地震计的参数稳定性分析

从理论上定量分析机械摆和环路滤波等开环诸参数变化对速度传感反馈地震计闭环参数的影响.研究指出,在环路设计中可半自由选取的开环阻尼取值对参数稳定性有重要影响.过大或过小的开环阻尼取值均可能造成参数稳定性急剧变差,影响地震计在只标不调的状况下长期连续稳定工作.     

On the calibration of feedback broadband seismometer FBS-3A with current signal

IntroductionWith the time passing by and the environment changing, the characteristics of the components in a seismometer may change a little to some extent because of some certain reasons. Therefore the reliability of a sensor(s output may lower the reliability and a wrong result may also be produced if these changes are not realized and controlled or adjusted in time. Hence, the seismometers must be calibrated either before leaving factory or in use, so as to check the parameters and the cha…     

FBS-3A型反馈式宽频带地震计电流标定方法研究

随着时间的推移和环境条件的缓慢变化，地震计各部件的性能参数会有所改变，及时了解这种变化并加以控制和调整，有助于提高地震计输出结果的可信度．所以，一台地震计无论在交付使用前，还是在使用过程中，都需要进行标定．目前，比较常用的标定方法有方波电流标定和正弦电流标定．本文从系统分析的角度出发，在分析得到地震计传递函数的基础上，将方波电流标定和正弦电流标定过程进行理论抽象，进而在复频域对两种电流标定过程进行仿真推导；并在此基础上，讨论了方波电流标定输出曲线与地震计固有参数之间以及正弦电流标定的稳态输出与标定电流之间的关系，并且论述了两组特定频率正弦电流的标定输出之间的关系．最后，作为理论分析在实践中的具体应用，给出了两种电流标定过程在实际工作中的应用方法．本文旨在阐明两种常用的电流标定方法的物理意义，对地震计的调试及应用有积极的参考作用．      

Identification of Mining Blasts at Mid- to Far-regional Distances Using Low Frequency Seismic Signals

—?This paper reports results from two recent monitoring experiments in Wyoming. Broadband seismic recordings of kiloton class delay-fired cast blasts and instantaneous calibration shots in the Black Thunder coal mine were made at four azimuths at ranges from 1° to 2°. The primary focus of this experiment was to observe and to explain low-frequency signals that can be seen at all azimuths and should routinely propagate above noise to mid-regional distances where most events will be recorded by International Monitoring System (IMS) stations.¶The recordings clearly demonstrate that large millisecond delay-fired cast blasts routinely produce seismic signals that have significant spectral modulations below 10?Hz. These modulations are independent of time, the azimuth from the source and the orientation of the sensor. Low-frequency modulations below 5?Hz are seen beyond 9°. The modulations are not due to resonance as they are not produced by the calibration shots. Linear elastic modeling of the blasts that is guided by mine-blast reports fails to reproduce the fine detail of these modulations but clearly indicates that the enhanced “spectral roughness” is due to long interrow delays and source finiteness. The mismatch between the data and the synthetics is likely due to source processes, such as nonlinear interactions between shots, that are poorly understood and to other effects, such as variations of shot time and yield from planned values, that are known to be omnipresent but cannot be described accurately. A variant of the Automated Time-Frequency Discriminant (Hedlin, 1998b), which uses low-frequency spectral modulations, effectively separates these events from the calibration shots.¶The experiment also provided evidence that kiloton class cast blasts consistently yield energetic 2–10 second surface waves. The surface waves are strongly dependent on azimuth but are seen beyond 9°. Physical modeling of these events indicates that the surface waves are due mainly to the extended source duration and to a lesser extent to the slap-down of spalled material. The directionality is largely a path effect. A discriminant that is based on the partitioning of energy between surface and body waves routinely separates these events from the calibration shots.¶The Powder River Basin has essentially no natural seismic activity. How these mining events compare to earthquake observations remains to be determined.