SOME ASPECTS OF HANDLING VELOCITY INVERSION AND HIDDEN LAYER PROBLEMS IN SEISMIC REFRACTION WORK*

There are two types of masked layers in seismic refraction work: the velocity reversal (low-velocity layer) and the hidden layer (insufficient velocity contrast or layer thickness). On the basis of an analytical formulation of the general case of a masked layer under an overburden of plane and parallel multiple refractors the two limiting cases are discussed: the solution resulting from an uncritical interpretation of the measured time-distance curve and the blind zone solution. Between these two limiting cases there is a variety of possible masked layer solutions. These no-blind zone solutions—as well as the blind zone solution itself—are formulated separately for the velocity inversion and the hidden layer case. For the evaluation of some no-blind zone solution a diagram is presented which can be used for any case of multiple refractors in the overburden of the masked layer. However, it is only for the three- and the four-layer case that a blind zone interpretation by use of diagrams is advisable. Such diagrams are presented together with the basic sets of formulae which contain as parameters only ratios of velocities and layer thicknesses. As the velocity of the masked layer is usually unknown the diagrams are principally constructed to show the dependence on the masked layer velocity. This is useful for estimation of the largest possible error.     

THE ABEL-FOURIER METHOD OF HANKEL TRANSFORMATION: APPLICATIONS TO SEISMIC DATA*

The formal equivalency between a Hankel transform and an Abel transform followed by a Fourier transform is used as a basis for the computation of synthetic seismograms and for performing plane-wave decomposition of both synthetic and field seismograms. The Abel-Fourier method performs better for near-offset or small ray-parameter, although at greater computational effort than calculations based upon the asymptotic Hankel transform.     

地震记录的广义分维及其应用

根据分形理论,对不同信噪比地震记录的分维特征进行了分析,指出地震记录中噪声背景与信号部分具有不同的分维尺度,地震道时间序列的分维数值与计算时所用的测量尺度有关,因此,可利用广义分维的概念计算地震记录的分数维.地震记录广义分维大大提高了分形算法在计算机自动识别地震波震相时的抗噪声能力.最后用本文方法对实际地震记录进行了有效的初至波自动拾取.     

地震记录的广义分维及其应用

根据分形理论,对不同信噪比地震记录的分维特征进行了分析,指出地震记录中噪声背景与信号部分具有不同的分维尺度,地震道时间序列的分维数值与计算时所用的测量尺度有关,因此,可利用广义分维的概念计算地震记录的分数维.地震记录广义分维大大提高了分形算法在计算机自动识别地震波震相时的抗噪声能力.最后用本文方法对实际地震记录进行了有效的初至波自动拾取.     

考虑不确定性的地震危险性分析方法及其应用

本文讨论了目前地震危险性分析过程中的不确定性及其对危险性分析结果的影响。引入“逻辑树”方法处理了四川某工程场地的地震危险性,最后用三种方法给出了地震危险性分析结果。     

地震勘探问题的一种新模型及其算法

本文针对地震勘探中对地层介质的识别问题,提出了一种新的数学模型:用双曲型方程Cauchy问题代替混合问题。得到一种逐层递推的快速反演算法,取得了较好的计算效果。     

地震勘探问题的一种新模型及其算法

本文针对地震勘探中对地层介质的识别问题,提出了一种新的数学模型:用双曲型方程Cauchy问题代替混合问题。得到一种逐层递推的快速反演算法,取得了较好的计算效果。     

地震调查工作中有关烈度鑑定的一些问题

地震在不同的地质、地形、土质及地下水位等条件下,产生不同的影响。不同地区内各种条件所佔的比重不同,而彼此之间又相互影响;因此在鑑定烈度时,便造成许多困难。但是,如果结合各现象的产生环境,深入分析,全面地与烈度表进行对比,常能得出比较一致的数值。在目前国家建设期间,鑑定6度至10度的地震区域特别     

地震调查工作中有关烈度鑑定的一些问题

地震在不同的地质、地形、土质及地下水位等条件下,产生不同的影响。不同地区内各种条件所佔的比重不同,而彼此之间又相互影响;因此在鑑定烈度时,便造成许多困难。但是,如果结合各现象的产生环境,深入分析,全面地与烈度表进行对比,常能得出比较一致的数值。在目前国家建设期间,鑑定6度至10度的地震区域特别     

声子波及其在地震波资料分解中的应用

声子波是由声波波动方程的解构成的一种物理子波,如果不考虑吸收和散射,声子波的传播是相当简单的;相反地,数学子波的传播即使在均匀介质中也是极其复杂的.作为波动方程的解,声子波比一般的数学子波更能有效地应用于复杂声波和地震波的分解和分析.本文从Kaiser的声子波理论出发,给出了通过分别引入点源波形的复时间函数和点源虚时间坐标来构成声子波的两种解释,并对点源模型的合成地震图和实际复杂模型的地震波资料进行了时-空域的声子波变换,说明了声子波应用于地震波资料分解的有效性.     

声子波及其在地震波资料分解中的应用

声子波是由声波波动方程的解构成的一种物理子波,如果不考虑吸收和散射,声子波的传播是相当简单的;相反地,数学子波的传播即使在均匀介质中也是极其复杂的.作为波动方程的解,声子波比一般的数学子波更能有效地应用于复杂声波和地震波的分解和分析.本文从Kaiser的声子波理论出发,给出了通过分别引入点源波形的复时间函数和点源虚时间坐标来构成声子波的两种解释,并对点源模型的合成地震图和实际复杂模型的地震波资料进行了时-空域的声子波变换,说明了声子波应用于地震波资料分解的有效性.     

A THEOREM FOR DIRECT CURRENT REGIMES AND SOME OF ITS CONSEQUENCES *

For any direct current regime, the theorem holds, where φ_p is the total measured or calculated potential at any point P, φ is the potential distribution known a priori, r is the distance between P and any volume element dV, the gradients are evaluated at the element, and the current sources and sinks have finite dimensions. Thus, each space element behaves as a dipole of moment (1/4π) ?φdV and contributes its share of signal or potential accordingly. By suitable summation or integration, the contribution from any assigned portion of space to the total measured signal can be determined. Except for the chargeability factor m, the formula also establishes Seigel's initial postulate for the time domain induced polarisation theory. The contribution depends on the potential gradient, not the current density, and the integration extends over the entire space. Although an insulating target carries no current, it contributes a signal that is in general larger than normal by virtue of its higher potential gradient, and thus helps in creating an overall positive anomaly or resistivity high. On the other hand, an infinitely conducting target—even though it supports a larger amount of current than normal—contributes nothing to the measured signal as the potential gradient is zero everywhere inside. Thus, by contributing less than normal, a conducting target promotes the creation of what is usually a resistivity low. In all cases, the contributions from the space elements add up exactly to the measured or total calculated value. Some other consequences of the theorem are also discussed, especially in relation to a simple two-layer earth. For instance, the contribution from the upper half-space (air) turns out to be equal to that from the lower (real ground), for all observation points on the ground surface and for any ground configuration.     

龙陵大震震型及有关问题讨论

本文根据１９７６年龙陵大震三次主震由南向北的迁移特征以及３次主震及其强余震活动所反映的震源时空分别位于不同的震源区，但首尾相接，且各自有前震和余震。用立交模式和深部剪切蠕滑断层对龙陵大震发生在完整的花岗岩体内作了解释。用介质相对完整、区域压力大解释了主震发生时形成复式震源，以及余震相对发育持特征，对于复式震源提出了用各震源提出了用各震源断层长度累计总和求震级的方法。     

复杂盆地的地震勘探

在中国南方有一类中小型盆地,它们的特点是垂直方向的多层结构和水平方向的多级分割,形成复杂的构造格局。复杂性就在于沉积深厚,岩相多变;数度侵蚀,火成常见;断层不少,构造陡倾;起伏频繁,上下不符。因此产生了复杂的地震地质条件和探测的技术问题,诸如各类多次波,侧面波的干扰,复杂断层,各种不整合,尖灭带,速度多变,深层畸变等,造成取得古生代地层内部波组的困难。文中提出了解决这些问题的观点和措施。     

利用地震记录反演震源非均匀特征的一些问题

利用地震记录反演震源非均匀特征是目前强震地震学研究中的一个重要的课题。本文在总结现有文献的基础上，对与震源反演相关联的六个环节即震源模型及模型参数、格林函数计算、观测数据、反演准则与目标函数、初始模型与迭代方式、反演精度与分辨率等进行了初步阐述和分析，同时对地震源反演中存在的问题也进行了相应的讨论。     

复杂盆地的地震勘探

在中国南方有一类中小型盆地,它们的特点是垂直方向的多层结构和水平方向的多级分割,形成复杂的构造格局。复杂性就在于沉积深厚,岩相多变;数度侵蚀,火成常见;断层不少,构造陡倾;起伏频繁,上下不符。因此产生了复杂的地震地质条件和探测的技术问题,诸如各类多次波,侧面波的干扰,复杂断层,各种不整合,尖灭带,速度多变,深层畸变等,造成取得古生代地层内部波组的困难。文中提出了解决这些问题的观点和措施。     

A METHOD OF ESTIMATING THE PARAMETERS OF TUNED MASS DAMPERS FOR SEISMIC APPLICATIONS

The optimum parameters of tuned mass dampers (TMD) that result in considerable reduction in the response of structures to seismic loading are presented. The criterion used to obtain the optimum parameters is to select, for a given mass ratio, the frequency (tuning) and damping ratios that would result in equal and large modal damping in the first two modes of vibration. The parameters are used to compute the response of several single and multi-degree-of-freedom structures with TMDs to different earthquake excitations. The results indicate that the use of the proposed parameters reduces the displacement and acceleration responses significantly. The method can also be used in vibration control of tall buildings using the so-called ‘mega-substructure configuration’, where substructures serve as vibration absorbers for the main structure. It is shown that by selecting the optimum TMD parameters as proposed in this paper, significant reduction in the response of tall buildings can be achieved. © 1997 John Wiley & Sons, Ltd.     

设计地震反应谱的双参数标定方法及其应用

近年的工程地震工作,如地震小区划、重大工程场地的危险性分析等,一般都要做设计谱标定。既反映局部场地条件,又反映地震环境的双参数标定设计谱的方法,已为工程界接受。作为该方法的应用,本文采用澜沧——耿马地震的强震资料,重新确定了设计反应谱的形状参数,给出了反映云南地区地震特性的设计谱,可供中、小型工业与民用建筑抗震设计时参考使用。     

折射波地震勘探中几个问题的探讨

在多年实际工作的基础上，从理论上对工作中的观测系统、资料处理方法、断层、ｔ。闭合等四个方面论述了存在的问题及相应的解决方法。