地震波的时间反转以及非线性佯谬述评

为了探讨动力学计算仿真在地学中应用的可行性 ,我们已经采用非线性动态有限元 ( Non-linear Dynamical FEM)方法作了一系列的初步研究。在关于波的遍历特性的研究中 ,提出用波的遍历特性来概括非线性动力系统例如地壳块体的复杂性 [1- 2 ] ,并从这个认识出发 ,用动力学仿真方法研究了在这种混沌性脉冲响应系统中的 L ame波及其时间反转过程 ,还研究了三维非均匀、有内部界面的岩石介质的时间反转效应。通过预研认为 ,运用时间反转原理 [3 ]在大尺度的地壳块体中实现波能量在空间的聚焦和时间上集中具有可信的物理依据 [4 ] 。地壳中波的…     

基于机器学习的时间反转散射体检测方法

地下小尺度散射体的检测和识别对于提高地震勘探的分辨率具有重要意义,目前业界普遍采用绕射波分离及成像方法检测地下散射体,而绕射波成像的质量主要取决于绕射波和反射波波场分离的程度.本文将被动源震源定位问题中常用的时间反转原理引入到地下散射体检测中,首先通过分析被动源和主动源模型反传波场的聚焦状态,验证了时间反转原理应用于地...     

甘—青—川块体和小金地震的时间节律研究

对1989，1991年四川小金地，三次强震的时间节律研究结果表明，每次强震前的小震序列均显示出明显的昼液周期（即横向时间节律），自1988年开始，到1989年逐渐趋向标准化，1991年第三次强震之的,逐渐消失，因此，可利用小震时间序列从无序－有序的演变过程,为强震的预测判断提供一种新的依据，从甘，青，川块体范围强震活动的历史分析还发现强度活动具有明显的纵向时间节律，即活跃期与期之比十分接近0．618，这个协调值可作为平衡期与活跃期的一个判定指标。     

基于站间天然电磁场单位脉冲响应的大地电磁时间序列去噪方法

针对天然大地电磁场信号在人文活动密集地区易受噪声干扰的问题,本文提出利用两个同步测点天然电磁场时间序列之间的单位脉冲响应,合成本地点受干扰时段的数据,从而去除大地电磁噪声.首先,选择高信噪比时段的数据,采用最小二乘法,估算本地点与参考点之间的单位脉冲响应,再根据卷积定律,结合参考磁场合成本地点的磁场和电场.最后用合成数据替换含噪声时段数据,实现时间域去噪.实测高信噪比数据和含噪数据的处理结果表明,该方法可以高精度合成本地点磁场与电场信号,有效去除本地点电场和磁场噪声,包括相关噪声,提高大地电磁数据质量.     

非线性吸收的热粘性流体中时间反转脉冲的振幅衰减

无损介质中的线性波动方程在时间上是可逆的，换言之，对于每个解p(x,t)都存在一个关于时间对称的真实解p(x,-t)。分析表明，时间反转同样适合于无损非线性波动方程。然而当存在损耗时，这两种情形都不再遵守时间反转不变性。考虑到非线性的传播损耗不容忽视；同时它们是避免出现多值波形的必要条件。对非线性波动方程的进一步分析显示，即使对于无损耗非线性声波，对波列单元上的反转信号的放大仍然会导致时间反转不变性的损失。本文用数字模拟技术描述了在一种能量吸收性的流体介质中，非线性对有效聚焦的性能的影响，此时时间反转系统只就一个目标进行聚焦。我们同时考虑了反向传播脉冲的振幅与到达时间这两个因素。数值模拟结果证实，波列上（伴随能量吸收的）产生的谐波与振幅放大对时间反转系统形成高强度重建声场带来了不利影响。     

甘－青－川块体和小金地震的时间节律研究

对１９８９、１９９１年四川小金地区，三次强震的时间节律研究结果表明：每次强震前的小震序列均显示出明显的昼夜周期（即横向时间节律）．自１９８８年开始，到１９８９年逐渐趋向标准化；１９９１年第三次强震之后，则逐渐消失。因此，可利用小震时间序列从无序－有序－无序的演变过程，为强震的预测判断提供一种新的依据。从甘、青、川块体范围强震活动的历史分析还发现强震活动具有明显的纵向时间节律，即活跃期与平静期之比十分接近０．６１８．这个协调值可作为平静期与活跃期的一个判定指标。     

用时间序列重建复杂系统动力学初探

用时间序列数据重建复杂系统动力学是非线性科学中的一个诱人课题。人们目前还无法直接给出自然界中许多现象产生的确定性规律或描述现象的微分方程,然而却可获得大量随时间变化的实测数据。据时间序列若能研究构成这些复杂现象的动力学特征,显然对揭示事物的本质是很有实际意义的。用地震时间序列重建地震复杂系统动力学,进而分析寻找表征地震过程的确定性规律,认识地震过程的动力学行为,深入研究地震预报,已成为一个引人瞩目的     

地壳块体应力场动力学演变过程仿真的初步研究

动用三维非线性动态有限方法,研究华北地壳块体对渤海、黄海潮汐水位变化的动态响应,得出该块体中各力学量随时间演变的数据结果以及动态、直观的三维体育场映象,并以此探索计算力学与地学综合研究的途径。从仿真模拟结果可以看出华北地区近期发生的几次在地震均在应力较大或应力变化剧烈的地点。由于动态载荷 的量级小,计算结果的应力绝对值也很小,因此,字种吻合表明较小的动态载荷下的动态响应揭示了际震构造的特征,显示了     

唐山地震区的地壳形变及强震重复时间预测

无论是地震前、还是地震后，在国内所有大震区中，唐山地震区的垂直形变资料都是最丰富的。作者在研究这些资料以后发现，唐山地震区的地壳形形变，在１９６７年以前经历了相当长的缓慢奖速的变化过程，１９６７－１９６９年全区出现了加速上升，紧接着转为快速下降和不稳定变化，根据宁河的流动水准测量资料推测，临震前地震断层发生了无震蠕动。大震发生时，全区出现了大幅度的同震形变。大震发生之后，地壳形变的速率随着余震的衰     

The time reversal effect of the impulse response of crust

IntroductionTime reversal effect is a kind of reversed dynamic process in a limited space or time interval, which can be realized artificially by resetting the boundary and loading conditions. In this case the time seems to be reversed and such effect therefore is called time reversal effect, which was first proposed in and applied to the field of ultrasonic. Although the focusing of ultrasonic wave has powerful effect, it is difficult to focus in an anisotropic or homogeneous medium. Fink (19…     

THE EFFECT OF HARD INTERLAYER THICKNESS ONTHE SITE SEISMIC RESPONSE

Studies on the effect of near-surface overburden soil layers on seismic motion have shown that the overburden soil layers have a significant impact on the seismic effect of the site due to the formation age, genetic type, thickness difference, structure, and dynamic characteristics of the soil layers. In this paper, the one-dimensional seismic response analysis of a nuclear power plant site containing a thick hard interlayer was conducted to discuss the influence of the hard interlayer thickness on the site seismic response, so as to provide a basis for determining the seismic motion parameters for seismic design of similar sites. Based on the engineering geological data of a nuclear power plant site, five models of one-dimensional soil-layer seismic response analysis were built, and the equivalent linear method of the one-dimensional site seismic response was applied to analyze the effect of the interlayer thickness on the peak acceleration and the acceleration response spectra of the site seismic response. The seismic response characteristics of the site and influence rules of the hard interlayer thickness are summarized as follows:1)Under different input seismic motion levels, the peak acceleration at the top of the hard interlayer was less than the input peak acceleration, and the peak acceleration at the ground surface of site was greater than the input peak acceleration. 2)Under the same input seismic motion, the ratios of the peak accelerations at the top of hard interlayer to the input peak accelerations were smaller than the ratios of the peak accelerations at the ground surface to the input peak acceleration, and these ratios first decreased and then increased gradually with the increase of the hard interlayer thickness; while for the same hard interlayer thickness, these ratios gradually decreased as the input peak acceleration increasing. 3)For the same input seismic motion, the ratios of the peak accelerations at the ground surface of site to those at the top of the hard interlayer increased gradually as the hard interlayer thickness increased; however, corresponding to different hard interlayer thicknesses, the variation characteristics of ratios which are the peak accelerations at the ground surface of site to those at the top of the hard interlayer were inconsistent with the increase of the input peak acceleration. 4)The hard interlayer had a significant influence on the short-period acceleration response spectrum and the thicker the hard interlayer was, the wider the influence frequency band would be; while for a special hard interlayer thickness, the influence frequency band is certain, and the hard interlayer had little effect on the acceleration response spectrum coordinates outside this frequency band, the longer the period is, the less the influence of the hard interlayer on the acceleration response spectrum coordinates. The seismic response characteristics of the site and influence rules of the hard interlayer thickness indicate that the hard interlayer thickness has a significant impact on the peak acceleration and the acceleration response spectra of the site seismic response, and the hard interlayer has obvious isolation effect at the seismic motion, and the increase of its thickness reduces the nonlinear effect of the site and leads to the wider influence frequency band. Meanwhile, the higher the input peak acceleration is, the stronger the nonlinear effect of the site, and it's remarkable that the soft layer overlying the hard interlayer has a significant amplification effect on the seismic motion.     

近场地震波最大反应到时的统计性研究

本文通过对地震反应谱的数值计算,以各种不同频率的最大反应到时为样本进行概率统计,给出了近场地震波不同频率的最大反应到时谱。为采用时程分析法进行结构抗震计算时持续时间的选取提供了依据。     

地震反应分析中的主时段

在计算反应谱及土层反应时,发现反应谱的形态和大小只受时程的主要部分控制,由此给出主时段的定义和确定主时段的方法。主时段的应用不仅可以大大缩短计算时间,而且能够成为持时的一种有物理意义的度量。     

ON THE IMPULSE RESPONSE OF AN AQUIFER

Abstract

The impulse response and the response to a unit step function of the onedirectional semi-infinite aquifer is given, derived from the approximate partial differential equation of the ground water flow. An example is presented.     

地震时间序列的突变分析

采用Ｍａｎｎ－Ｋｅｎｄａｌｌ非参数方法检验了陕西及邻省的历史及现今地震序列，发现存在若干突变点，在其前后地震频次和强度发生非连续时间变化。这个研究有助于地震演变规律认识。     

ON DIRECT RECOVERY OF THE IMPULSE RESPONSE*

The deconvolution equation is solved in the z-transform domain directly for an impluse response. The principal assumption is the odd-depth model: two-way traveltimes to the boundaries are constrained to be odd integers only. It is further assumed that the length of the wavelet sequence is known to be less than half the length of the data sequence. An inverse of the impulse response is constrained by the zero samples of the source function. The resulting underdetermined set of equations is supplemented with the equations provided by the odd-depth model. The impulse response is found from the inverse by polynomial division.     

端承桩基础轴向地震反应分析

本文对分层弹性地基中端承桩基础通过特性分析建立了合理的力学模型，通过动力分析，给出了端承桩基础轴向自振特性及在竖向地震载荷作用下强迫反应的解析解。文中的解析公式为分层弹性地基中的端承桩基础轴向动力反应分析提供了一种新的解析方法。     

GEOMORPHOLOGICAL THEORY OF THE HYDROLOGICAL RESPONSE

The geomorphological theory of the hydrological response, originated by Rodriguez-Iturbe and Valdes, is reviewed with reference to the general framework of the formulation of transport processes by travel time distributions. This review, by no means exhaustive of the publications on this subject, collects in a reasonably organic manner some relevant theoretical developments and a few significant applications.     

阻尼耗能在结构弹塑性地震反应中的作用

本文用计算分析的方法研究了结构在弹塑悸地震反应过程中的阻尼耗能与塑性耗能的数量关系问题。