地震波模型試驗仪器的电子线路

本文討論了一套配合現成示波器进行地震波模型試驗用的电子线路。綫路的前置放大器的通頻带为2-700千周,增益为60分貝,輸入端短路噪声电压为2.5微伏.高压脉冲发生器产生一个寬度为2-33微秒的幅度为500伏的矩形电脉冲。时标电路产生2,10,50微秒三組吋标,基本吋标（2微秒）可由稳定的石英振蕩器随时加以校准。整个线路此較簡单、灵活,一般地球物理实驗室試制容易,且可根据具体要求加以变动。     

三层介质模型震相分析与地壳结构

本文用超声波方法在层状介质中进行地震模型试验研究,试图寻找一种解决某些地壳和地球内部构造问题的方法。试验中使用SYC-2型声波岩石参数测定仪,换能器是用锆钛酸铅（Pb（Ti,zr）O₃）晶体制成,共有三个换能器,一个做发射探头,两个做接收探头。波形由双踪示波管显示,以利于波形对比和震相追踪。 用黄蜡、石膏和有机玻璃等板材制造一个三层介质地壳模型,来模拟辽南地区的地壳结构,并将发射探头放在上层模型的侧面,成功地模拟了有深度的震源。文中详细分析了该模型中的主要震相,并与辽南地区的天然地震进行了对比,从而为辽南地区的地壳结构提供了一个旁证,也为今后对比某地区的地壳结构提供了一种新的方法。     

具有孔边裂纹的岩石厚壁筒试件的破裂特征

用五种应力途径对由五种岩石制备的孔边有予裂纹的厚壁筒试件进行实验,研究上述条件下岩石的破裂特征。结果表明:对含径向并贯穿轴向裂纹的试件,其破裂沿裂纹方向,为典型的张开型破裂;含与定直径成45°角并贯穿轴向裂纹的试件,破裂亦呈张开型,其裂面始于裂纹前缘,但却折转约45°角与定直径近于平行;中心含与轴向成45°角的椭圆裂纹试件的破裂,仍沿裂纹面方向,为张开型与滑开型的复合破裂。     

南海北部区域构造和陆壳向洋壳的转化

1.海底扩张和陆壳大洋化,均能形成洋壳。陆壳转化为过渡壳是大洋化的必经阶段。 2.航磁测区内的中央海盆,具有类似于大洋中海底扩张形成的对称磁异常条带。 3.在西沙北裂谷、莺歌海裂谷型拗陷,以及属于断陷盆地性质的珠一、珠二拗陷等地,有沿着断裂上升的类似于洋壳成分的地幔物质喷溢或在地壳上层侵位,那里的地壳都有不同程度的减薄,属于过渡型地壳。西沙北裂谷的“莫霍面”,比相邻的南北两侧高出约10公里。 4.在南海北部发生多中心微型扩张和大洋化。     

单裂缝不同传播方向Krauklis波振幅变化的实验研究

裂缝广泛分布于地壳岩石中并具有多尺度的特点,研究地震波在裂缝介质中的传播规律具有重要的科学意义和应用价值.含流体的裂缝中传播的Krauklis波(也曾被称为慢流体波、裂缝波、斯通利导波等)近年来逐渐成为地球物理学界的研究热点之一.本研究利用地震物理模型技术研究横波在单裂缝样品中传播时随传播方向变化的响应特征,在实验室用环氧树脂为基质构建模型样品,一个为不含裂缝的参考样品,一个为含直径30 mm、厚度0.2 mm的薄币状单裂缝的模型,利用0.5 MHz换能器测试了横波在模型中传播时透射信号的特征.实验结果显示在单裂缝样品中透射横波发生了波形的畸变和振幅降低,振幅谱显示透射信号的主频明显降低,在初至横波之后为具有一定能量的尾波.对尾波进行时频分析,发现在方位角较小时尾波能量较弱而方位角较大时尾波能量较强,尾波中信号的主频在0.1 MHz左右,与前人理论和实验研究结果一致.     

CSAMT勘探中场区、记录规则、阴影及场源复印效应的解析研究

由矢量位导出均匀大地表面上水平接地谐变电偶极子地下电磁场的闭合表达式, 将地层波和地面波显式地区分开来, 据此定义了与远区场和近区场对应的地面波区和地层波区. 对长期困扰CSAMT勘探工作者的记录点问题、阴影和场源复印效应问题给出了物理解释. 由地层波与地面波之比给出了定量划分场区的方法, 每一场分量最佳记录规则下的条件和判断是产生阴影和场源复印效应的前提. 山西沁水盆地CSAMT勘探覆盖点的推断结果表明, 阴影和场源复印效应是由地层波所携带的源与观测点之间、源下方真实地质情况的信息决定, 是可以利用的.     

单片机控制下地震勘探应答器集成音频声源级控制方法

以往地震勘探应答器控制方法,不能有效减少噪声对应答器集成音频存在的干扰,导致应答器音质存在杂音,影响使用效果。为此,提出单片机控制下地震勘探应答器集成音频声源级控制方法,构建基于单片机控制的地震勘探应答器,应答器包含了供电模块、主控模块、功放模块、匹配模块、接收模块、收发合置模块以及收/发换能器,采用单片机获取内部输出的工作情况,并基于稀疏正则化的集成音频声源布局优化方法,实现声源级控制。结果表明:所提方法能够有效强化单片机控制下地震勘探应答器集成音频效果,且去噪效果好,该方法控制下应答器工作线性度较优,能够为地震勘探提供更好的勘探方法和勘探设备。     

RESEARCH ON PASSIVE SERVO SEISMIC ROTATIONAL ACCELERATION SENSOR WITH LARGE DAMPING

Many strong motion records show that under the strong seismic vibration of, the torsional disfigurement of building structures is a common and serious damage. At present, there are no special sensors for measuring seismic rotation in the world. Most of the experts obtain rotational components through observing deformation, theoretical analysis and calculation. The theory of elastic wave and source dynamics also prove the conclusion that the surface of the earth will rotate when an earthquake occurs. Based on a large number of investigations and experiments, a rotational acceleration sensor was developed for the observation of the rotational component of strong ground motions. This acceleration sensor is a double-pendulum passive servo large-damped seismic rotational acceleration sensor with the moving coil transducer. When an earthquake occurs, the seismic rotational acceleration acts on the bottom plate at the same time. The magnetic circuit system and the middle shaft fixedly connected to the bottom plate follow the bottom plate synchronous vibration, and the moving part composed of the mass ring, the swing frame and the moving ring produces relative corners to the central axis. The two working coils mounted on the two pendulums produce the same relative motion with respect to the magnetic gaps of the two magnetic circuits. Both working coils at this time generate an induced electromotive force by cutting magnetic lines of force in the respective magnetic gaps. The generated electromotive forces are respectively input to respective passive servo large damper dynamic ring transducer circuits and angular acceleration adjusting circuits, and the signals are simultaneously input to the synthesizing circuit after conditioning. Finally, the composite circuit outputs a voltage signal proportional to the seismic rotational acceleration to form a seismic rotational acceleration sensor. The paper presents the basic principles of the rotational acceleration sensor, including its mechanical structure diagram, circuit schematic diagram and mathematical models. The differential equation of motion and its circuit equation are derived to obtain the expressions of the main technical specifications, such as the damping ratio and sensitivity. The calculation shows that when the damping ratio is much larger than 1, the output voltage of the passive servo large damping dynamic coil transducer circuit is proportional to the ground rotation acceleration, and the frequency characteristic of bandpass is wider when the damping ratio is larger. Based on the calibration test, the dynamic range is greater than or equal to 100dB and the linearity error is less than 0.05%. The amplitude-frequency characteristics, the phase-frequency characteristics and their corresponding curves of the passive servo rotational acceleration sensor are acquired through the calculations. Based on the accurate measurement of the micro-vibration of the precision rotating vibration equipment, the desired result is obtained. The measured data are presented in the paper, which verify the correctness of the calculation result. The passive servo large damping rotational acceleration sensor has simple circuit design, convenient operation and high resolution, and can be widely applied to seismic acceleration measurement of earthquake or structure.     

A viscous-spring transmitting boundary for cylindrical wave propagation in saturated poroelastic media

Based on the u–U formulation of Biot equation and the assumption of zero permeability coefficient, a viscous-spring transmitting boundary which is frequency independent is derived to simulate the cylindrical elastic wave propagation in unbounded saturated porous media. By this viscous-spring boundary the effective stress and pore fluid pressure on the truncated boundary of the numerical model are replaced by a set of spring, dashpot and mass elements, and its simplified form is also given. A u–U formulation FEA program is compiled and the proposed transmitting boundaries are incorporated therein. Numerical examples show that the proposed viscous-spring boundary and its simplified form can provide accurate results for cylindrical elastic wave propagation problems with low or intermediate values of permeability or frequency content. For general two dimensional wave propagation problems, spuriously reflected waves can be greatly suppressed and acceptable accuracy can still be achieved by placing the simplified boundary at relatively large distance from the wave source.     

3-D approximate inversion for transient electromagnetic soundings

IntroductionThe issues of forward and inverse interpretation for homogeneous half space models and layered models of the Earth have well been solved in trAnsient electromagnetic sounding (TEM), butinterpreting data from more complicated 2-D or 3-D models are difficult because their responsefunctions are complicated and expensive to calculate. For the sake of simplification, based on thetheories of smoke ring (Nabighian, 1979), we regard current lines in the Earth induced by transmitting sou…     

A local time-domain transmitting boundary for simulating cylindrical elastic wave propagation in infinite media

Finite element simulation of the time-dependent wave propagation in infinite media requires enforcing the transmitting boundary to replace the truncated far-field infinite domain so as to model the effect of the wave radiation towards infinity. This paper proposed a novel local time-domain transmitting boundary for simulating the cylindrical elastic wave radiation problem. This boundary is a mechanical model consisting of the spring, dashpot and mass elements, with the auxiliary degrees of freedom introduced, which is dynamically stable and easily implemented into the commercial finite element codes. Numerical analysis of the cylindrical elastic wave radiation problem indicates that the proposed transmitting boundaries with the order N=3 for cylindrical P and SV waves and with the order N=4 for cylindrical SH wave have very high accuracy, even when the artificial boundary at wave source. The proposed transmitting boundary with order N=0 can be applied approximately to the general two-dimensional infinite elastic wave problems that contain the more complex outgoing wave fields at artificial boundary than the cylindrical waves. The plane-strain Lamb problem is analyzed with the acceptable engineering accuracy achieved. On the other hand, the proposed transmitting boundary with higher order can be a tool to localize the temporal convolution that appears in an exact time-domain transmitting boundary for the general infinite wave problems. This potential applicability is mentioned.     

二维不均匀介质中点源P-SV波响应的有限差分近似算法

本文从一阶方程组形式的波动方程出发,发展了一种计算二维不均匀介质中点源P-SV波响应的近似方法。该方法通过引入线分布的应力作为震源,利用二维有限差分方法计算出线源响应,然后再经过波形校正和几何扩散校正得出相应的近似点源响应。通过把波形和振幅与精确解比较表明,该方法具有较好的精度。由于有限差分方法对于介质中速度和密度的分布没有特殊要求,另一方面,本文所给出的震源可以适用于位错点源、爆炸源或集中力源,因此上述方法十分适合于研究横向不均匀介质中的近场强地运动、爆炸振动或地震勘探等问题。     

瞬变电磁波测井边界远探测方法研究

随钻地质导向钻井的关键在于对边界的探测,为提高仪器探测深度,时谐源激励的电磁波测井方法通常采用降低频率、增大源距的方式.瞬变电磁波测井信号源的突然关断产生会产生感应涡流,涡流随时间向地层深部扩散,与时谐源激励方式相比,其探测深度更大且测量过程不受信号源的干扰.因此,本文提出一种时间域瞬变电磁波测井边界远探测方法,采用余弦变换的数值滤波算法,模拟层状地层同轴发射接收线圈的瞬变电磁波测井响应,结果显示,地层电导率越大,电磁波传播速度越慢,测量晚期感应电动势与地层电导率线性相关;通过定义层状介质总场与线圈系所在当前层背景场的差值可方便提取界面信息,对界面的探测距离可达数十米;瞬变电磁波测井响应受源距的影响很小,为利用短源距实现远探测提供了可能.瞬变电磁波测井与时谐源电磁波测井相比优势明显,在电磁波测井领域中应用前景广阔.     

A high-order time-domain transmitting boundary for cylindrical wave propagation problems in unbounded saturated poroelastic media

Based on the u–p formulation of Biot equation with an assumption of zero permeability coefficient, a high-order transmitting boundary is derived for cylindrical elastic wave propagation in infinite saturated porous media. By this transmitting boundary the total stresses on the truncated boundaries of a numerical model, such as a finite element model, are replaced by a set of spring, dashpot and mass elements, with some additionally introduced auxiliary degrees of freedom. The transmitting boundaries are incorporated into the DIANA SWANDYNE II program and an unconditionally stable implicit time integration algorithm is adopted. Despite the assumption made in the derivation of the transmitting boundary, numerical examples show that it can provide highly accurate results for cylindrical elastic wave propagation problems in infinite saturated porous medium in case the u–p formulation is applicable. Although the direct applications of the proposed transmitting boundary to general two dimensional wave problems in infinite saturated porous media are not highly accurate, acceptable accuracy can still be achieved by placing the transmitting boundary at relatively large distance from the wave source.