闭环极点补偿式拾振器

利用闭环极点补偿技术，改善高频地震检波器的低频特性和扩大位移振幅量程，使之满足超低频，宽频带，大量程的工程振动测量要求。     

921型超低频有源伺服式速度,位移计

本介绍一种在很小体积的往复式摆上采用有源伺服技术实现超低频大幅值测量用的速度计、位移计，它可在多个频带测量速度和位移。最低频率可达０．０４Ｈｚ，最大可测位移为±１５ｍ。它可用于海浪浪高、抽油机行程、高柔结构的超低频大位移测量。该仪器于１９９２年获得国家专利，并获得中国专利博览会银奖。     

941B型超低频测振仪的研究

本文介绍了941B型超低频测振仪的原理和技术性能.将无源电路补偿技术应用于优化设计的往复式小质量摆上,实现了测量量程和低频特性的扩展,克服了回转摆式低频测振仪簧片易损、需要调零、频带较窄的缺点.该仪器不仅可用来测量地面和工程结构的超低频振动的加速度、速度和位移,而且可用于爆破、冲击等较高频的振动测量.     

用于深部探测的地震检波器低频拓展技术

利用地震探测的方法获得地球深部精细构造,从而增强深部资源勘探和重大地质灾害预测能力,是目前地球物理学研究的热点之一.本文简要回顾了国内外深部地震探测研究的历史,分析和解释了在精确深部地震探测中保护低频地震信号的重要性和必要性.在此基础上进一步阐述了地震检波器的低频特性对获取高质量深部地震数据的意义,重点归纳总结了如何利用伺服技术、闭环极点补偿技术以及力平衡反馈技术实现地震检波器的低频拓展,并以典型深部地震探测项目为例介绍了低频检波器在深部探测中的应用及主要取得的成果.最后,结合新型材料和新型加工技术,指出了未来深部地震检波器发展的主要方向.     

891型测振仪无源伺服技术的应用

891型测振仪由拾振器和放大器组成。采用拾振器无源伺服技术,选取小运动质量的高自振频率往复摆,扩大了使用频率范围和幅值测量范围;采用了微型开关,与放大器放大、积分结合,实现了一机多用的目的,可测量位移、速度和加速度。使用频率范围为0.5—100HZ,最大可测位移为150mm,最大可测加速度为80m/s~2。可用于结构脉动测量、桥梁振动测量、桩基动测、波速测量、爆破中距离测量等。     

垂直磁极变频测深的低频特性和高阻层的穿透问题

在本文中,我们对垂直磁偶极变频测深中高阻屏蔽层的穿透和视电阻率的低频特性进行了理论上的研究,给出了有关的近似公式,以及应用这些公式的条件。为了验证所给出的近似公式的正确性及其误差的大小,通过一些实例,将它们与电子计算机算出的准确结果进行了比较。     

垂直磁极变频测深的低频特性和高阻层的穿透问题

在本文中,我们对垂直磁偶极变频测深中高阻屏蔽层的穿透和视电阻率的低频特性进行了理论上的研究,给出了有关的近似公式,以及应用这些公式的条件。为了验证所给出的近似公式的正确性及其误差的大小,通过一些实例,将它们与电子计算机算出的准确结果进行了比较。     

水平电偶极变频测深的低频特性和对高阻层的穿透问题

本文对水平电偶极变频测深中高阻屏蔽层的穿透和视电阻率的低频特性进行了理论上的研究,给出了有关的近似公式以及应用这些公式的条件。为了验证这些近似公式的正确性以及了解它们误差的大小,并通过一些实例将它们与电子计算机算出的准确结果进行了比较。     

水平电偶极变频测深的低频特性和对高阻层的穿透问题

本文对水平电偶极变频测深中高阻屏蔽层的穿透和视电阻率的低频特性进行了理论上的研究,给出了有关的近似公式以及应用这些公式的条件。为了验证这些近似公式的正确性以及了解它们误差的大小,并通过一些实例将它们与电子计算机算出的准确结果进行了比较。     

基于MEMS传感器的速度型地震计技术研究

低功耗、微型化、芯片化、智能化、网络化、低成本高可靠以及全频带观测是地震传感器发展的方向,利用MEMS技术可以集成满足现代传感器要求的"芯片仪器",便于布设低成本、高密度的智能化现代传感器网络.本文提出了从MEMS加速度计经积分放大器获得速度地震计的技术方案,研究指出:1)为获得50Hz有效带宽内动态范围能达到电源电压的满摆幅输出,折合后级的放大倍数在内,积分放大器的积分时间常数只能是小于3.2ms;2)为克服积分器的漂移和噪声,提出了斩波多相积分技术;3)采用成品MEMS加速度计研制的速度型地震计,动态范围可达94dB,带宽在实测的100s～100Hz内响应平坦.提出了以MEMS加速度计的差分电容作为斩波多相积分器的斩波部件而研制高分辨率MEMS速度地震计的技术方案.     

The effects of conduit length and acoustic velocity on conduit resonance: Implications for low-frequency events

Low-frequency seismic events at volcanoes are modelled as the seismic wavefield from a magma-filled conduit embedded in a solid country rock using a finite difference method. The effects of varying the conduit length and the impedance contrast between the magma and the country rock are examined, generating a range of possible signals. Short-windowed spectrograms are used to look at the time–frequency relationships within the events in detail, and some of the possible variations are identified using a series of schematic spectrograms. The numerical results are compared to examples of observed seismic data from Soufrière Hills Volcano, Montserrat. While the spectra of the observed events are often different to the spectra of the numerical results, the spectrograms have similar features and show that the low-frequency events from Montserrat are composed of discrete subevents.     

Advanced insights into sources of vertical velocity in the ocean

Estimating vertical velocity in the oceanic upper layers is a key issue for understanding ocean dynamics and the transport of biogeochemical elements. This paper aims to identify the physical sources of vertical velocity associated with sub-mesoscale dynamics (fronts, eddies) and mixed-layer depth (MLD) structures, using (a) an ocean adaptation of the generalized Q-vector form of the ω-equation deduced from a primitive equation system which takes into account the turbulent buoyancy and momentum fluxes and (b) an application of this diagnostic method for an ocean simulation of the Programme Océan Multidisciplinaire Méso Echelle (POMME) field experiment in the North-Eastern Atlantic. The approach indicates that w-sources can play a significant role in the ocean dynamics and strongly depend on the dynamical structure (anticyclonic eddy, front, MLD, etc.). Our results stress the important contribution of the ageostrophic forcing, even under quasi-geostrophic conditions. The turbulent w-forcing was split into two components associated with the spatial variability of (a) the buoyancy and momentum (Ekman pumping) surface fluxes and (b) the MLD. Process (b) represents the trapping of the buoyancy and momentum surface energy into the MLD structure and is identified as an atmosphere/oceanic mixed-layer coupling. The momentum-trapping process is 10 to 100 times stronger than the Ekman pumping and is at least 1,000 times stronger than the buoyancy w-sources. When this decomposition is applied to a filamentary mixed-layer structure simulated during the POMME experiment, we find that the associated vertical velocity is created by trapping the surface wind-stress energy into this structure and not by Ekman pumping.     

横向各向同性地层井孔伪瑞利波、弯曲波、螺旋波的低频极限速度

在多极源声测井中, 低频弯曲波或螺旋波被广泛应用于测量地层的横波速度. 前人的研究已证明在各向同性地层中井孔伪瑞利波、弯曲波及螺旋波的低频极限速度都等于地层横波速度. 大量的数值计算结果似乎表明此结论在横向各向同性（TI）地层情况下也能成立, 但缺乏理论证明. 本文在井孔平行于TI弹性地层对称轴的模型下, 考察了井内声源激发的波在流-固边界上的反射和透射情况, 阐述了非泄漏模式导波产生的必要条件并讨论了其速度上限值. 我们发现在各向异性参数满足一定条件的TI地层中,导波速度的低频极限值小于沿井孔方向上的横波速度. 通过对井孔导波的频散分析以及对时域全波列的数值模拟, 论证了在这类地层中进行多极源声测井时,不可能根据弯曲波或螺旋波的到达时间准确获取地层的横波速度值.     

Comparison of four techniques for estimating temporal change of seismic velocity with passive image interferometry

Passive image interferometry (PII) is becoming a powerful tool for detecting the temporal variations in the Earth's structure,which applies coda wave interferometry to the waveforms from the cross-correlation of seismic ambient noise.There are four techniques for estimating temporal change of seismic velocity with PII:moving-window cross-correlation technique (MWCCT),moving-window cross-spectrum technique (MWCST),stretching technique (ST) and moving-window stretching technique (MWST).In this paper,we use the continuous seismic records from a typical station pair near the Wenchuan MS8.0 earthquake fault zone and generate three sets of waveforms by stacking cross-correlation function of ambient noise with different numbers of days,and then apply four techniques to processing the three sets of waveforms and compare their results.Our results indicate that the techniques based on moving-window (MWCCT,MWCST and MWST) are superior in detecting the change of seismic velocity,and the MWCST can give a better estimate of velocity change than the other moving-window techniques due to measurement error.We also investigate the clock errors and their influences on measuring velocity change.We find that when the clock errors are not very large,they have limited impact on the estimate of the velocity change with the moving-window techniques.     

压电智能传感结构在土木工程中的研究和应用

压电智能结构是目前智能结构的研究热点之一,用途广阔,并取得了丰富的研究成果：文章综述了压电智能结构中的传感器／驱动器及其系统和基于压电传感器的常用监测方法以及在土木工程中的研究和应用等,并对压电智能传感结构工程实用化的前景提出看法。     

饱和砂土地铁车站的振动台试验研究

地震作用下,饱和砂土地层地铁车站的动力反应特征是城市轨道工程抗震的关键问题。以太原地铁新近沉积粉细砂地层地铁工程为对象,通过模拟地震运动输入的饱和砂土地基地下结构的振动台模型试验,分析了不同峰值加速度地震作用下饱和砂土与地下结构相互作用的动力反应性状。研究了地震波作用的放大效应与频率特征,动孔压比增长发展过程和液化区域分布,以及动土压力的变化规律。表明加速度放大系数为1.5~2.0;0.1~0.25g峰值加速度地震作用下饱和砂土均产生动孔隙水压力累计发展;0.3g峰值加速度地震作用下饱和砂土产生液化,抑制了土与地下结构的振动放大效应,地表面大量冒水,结构模型出现了明显上浮,地下结构两侧产生震陷。     

莺东斜坡带速度分析方法研究及速度影响因素分析

莺歌海盆地是一个有勘探潜力的盆地,尤其是莺东斜坡带附近有良好勘探前景.但是由于研究区位于莺东斜坡带附近,因此构造解释具有相当的难度,尤其是由时间解释转化为构造解释有难度,需要有一个准确的速度来进行时深转换.基于此原因,本文首先介绍了速度谱拾取过程中的一些难点及解决方法;其后是速度分析取得的成果,通过DepthTeam形成速度体,从点、面、体三个不同角度证明了速度谱拾取过程中速度的准确性以及速度体的实用性;最后对单井和地层的速度进行了统计分析,总结了本区影响速度变化的主要因素.     

地震勘探中速度信号转化为加速度信号的分析及应用

目前,广泛应用在地震勘探中的检波器类型主要是速度型检波器和加速度型检波器,分别接收振动的速度信息和加速度信息,不同类型的检波器接收的地震资料具有不同的响应特征.在滩浅海地震勘探中,不同的地表区域使用不同类型的检波器接收,滩上使用速度检波器接收、海中使用加速度检波器和速度检波器组成的"双检"检波器接收,所以存在着两类检波器资料的拼接、融合处理问题.本文在理论上通过速度检波器和加速度检波器机电转化原理不同,跟踪不同物理量说明了两种信号之间的关系,并通过理论分析、实际的地震数据资料分析和证明了速度信号通过微分计算转化为加速度信号的可行性和正确性,并进行了相应的对比和验证.在滩浅海以及浅海地震勘探中应用加速度检波器和速度检波器联合采集后,应用这种转换方法进行资料的拼接处理和融合处理,得到的地震剖面质量得到了很好的提升.     

Mapping the properties of low-frequency microseisms for seismic hazard assessment

The structure of low-frequency seismic noise in the range of periods from 2 min to 500 min is studied from the data of continuous seismic monitoring at 77 seismic stations of the F-net broadband network in Japan from the beginning of 1997 to May 15, 2012. A new statistical characteristic of seismic noise is suggested, namely, the minimal normalized entropy En of the distribution of squared orthogonal wavelet coefficients. This parameter of seismic noise is analyzed in conjunction with the multifractal statistics—the support width of the singularity spectrum, Δα, and the generalized Hurst exponent, α*, which were extensively used by the author in the previous works for analyzing the low-frequency seismic noise. The method for constructing the maps of spatial distribution of Δα, α*, En, and their aggregated normalized value over the time windows with a given length is proposed. The maps are constructed by averaging the succession of the elementary charts, each of which corresponds to a day of observations. It is shown that, for the islands of Japan, the reduction in Δα and α* and the increase in En outline the area of the forthcoming mega earthquake of March 11, 2011, with M = 9 (Tohoku earthquake). According to the analysis of about a year’s worth of data after this event, the region south of Tokyo (Nankai trough) is still dominated by decreased Δα and α* and increased En. This gives grounds to hypothesize that this region remains at a high level of seismic threat since the accumulated stresses were incompletely released by the Tohoku earthquake. Drawing an analogy to the behavior of the coefficient of correlation between Δα and α*, we may suppose that there is an increased probability of a strong earthquake occurring in the second half of 2013 or the first half of 2014. Constructing the averaged maps of the distributions of seismic noise parameters and their aggregated value in a moving time window is suggested as a new method for dynamical assessment of seismic hazards.