一种ARMA模型地震子波提取方法研究

在地震子波因果、混合相位的假设下,本文突破突破滑动平均(MA)型假设的地震子波提取技术,提出一种阶数吝啬的自回归滑动平均(ARMA)模型对地震子波进行参数化准确建模的方法.针对地震子波ARMA模型定阶困难,超定阶容易造成计算量大、运算速度慢,欠定阶不能满足精确子波的要求,本文采用基于自相关函数的奇异值分解(SVD)法确定AR模型阶数,同时将信息量准则法与高阶累积量法相结合,提出了一种新的MA模型定阶法.数值仿真和实际地震数据处理结果表明,本文所用方法可以有效地压制加性高斯色噪声,信息量准则法可有效提高MA定阶的准确率,在保证子波精度的同时尽可能降低模型阶数,实现运算高效率.     

一种基于信息反馈的高精度地震子波提取方法

针对实际地震数据处理过程中参数化模型方法提取的子波与实际地震子波的一致性及其子波提取方法的有效性问题,本文提出一种基于信息反馈思想的地震子波提取方法.该方法利用提取的子渡合成地震记录,对合成地震记录和原始地震记录中的关键属性、特定参数进行分析比较,并将比较结果作为反馈信息作用于地震子波提取过程.理论研究与分析结果表明,...     

基于带状混合矩阵ICA实现地震盲反褶积

基于对地震反褶积本质上是一个盲过程的认识，引入高阶统计学盲源分离技术——独立分量分析（ICA）实现地震盲反褶积.在无噪声假设条件下，利用地震记录时间延迟矩阵和地震子波带状褶积矩阵，将地震褶积模型转化为一般线性混合ICA模型，采用FastICA算法，将带状性质作为先验信息，实现所谓带状ICA算法（B\|ICA），得到个数与子波算子长度相等的多个估计反射系数序列和估计子波序列，最后利用褶积模型提供的附加信息从中优选出最佳的反射系数序列及相应的地震子波.模型数据和实际二维地震道数值算例表明：对于统计性反褶积，在不对反射系数作高斯白噪假设，不对子波作最小相位假设的所谓“全盲”条件下，基于ICA方法（反射系数非高斯分布，地震子波非最小相位）可以较好解决地震盲反褶积问题，是基于二阶统计特性的地震信号统计性反褶积方法的提升，具有可行性和应用前景.     

基于高阶累积量ARMA模型线性非线性结合的地震子波提取方法研究

在地震子波非因果、混合相位的假设下,本文应用自回归滑动平均(ARMA)模型对地震子波进行参数化建模,并提出利用线性(矩阵方程法)和非线性(ARMA拟合方法)相结合的参数估计方式对该模型进行参数估计.在利用矩阵方程法确定模型参数范围的基础上,利用累积量拟合法精确估计参数.理论分析和仿真结果表明,该方式有较好的适应性：一方面提高了子波估计精度,避免单独使用矩阵方程法在短数据地震记录情况下可能带来的估计误差;另一方面提高了子波提取运算效率,降低了ARMA模型拟合方法参数范围确定的复杂性,避免了单纯使用滑动平均（MA）模型拟合法估计过多参数所导致的运算规模过大问题.初步应用结果表明该方法是有效可行的.     

深度域叠前弹性波阻抗反演（英文）

叠前深度偏移的广泛应用产生了大量的深度域地震数据,提供了深度域地震处理的数据基础,并为探索直接基于深度域地震数据的储层弹性参数反演提供了可能性。由于深度域地震子波存在与速度密切相关的特征,直接提取深度域地震子波存在困难,本文将深度域速度变换与脊回归方法结合,实现了深度域地震子波的确定性提取,将提取的深度域常速地震子波构建成依赖速度的空变地震子波,基于加权叠加思想,提出了深度域地震记录合成方法。再结合非线性共轭梯度算法,建立了基于深度域地震数据和模型驱动的深度域叠前波阻抗反演流程,不再进行额外的时间域和深度域之间的数据转换。深度域合成地震数据与实际地震资料的叠前波阻抗反演取得了较好的结果,表明该方法是可行的。该方法可作为深度域正演分析和叠前弹性参数反演的基础方法,为深度域反演方法的稳定性、精度和效率的进一步研究创造了条件。     

非平稳地震记录中时变子波提取方法研究

地震波在地下介质传播过程中,受近地表的非均质性和地层的非完全弹性影响产生散射和吸收衰减,使得地震记录具有非平稳性.因此对非平稳地震记录的研究需打破子波时不变的假设,更加真实地反映地震子波的传播特性,将有效提高地震子波估计精度.目前非平稳地震记录中提取地震子波的研究主要集中在两方面:对非平稳地震记录进行衰减补偿后采用常规方法提取地震子波;利用谱模拟或分段处理直接对非平稳地震记录进行时变子波提取.本文深入研究了衰减补偿方法与时变子波提取方法,对广泛应用于非平稳地震记录处理中的时频分析方法的优缺点进行归纳,并对谱模拟及分段处理方法的应用前景进行了展望。     

基于生成对抗网络的塔里木深层超深层叠前地震子波提取

深层超深层叠前地震子波的准确提取可有效提高全波形反演及叠前偏移成像等方法的准确性,对储层预测和油气分析具有重要意义.针对塔里木低信噪比叠前地震记录,本文提出一种基于生成对抗网络(GAN)的塔里木深层超深层叠前地震子波提取方法.结合柯东地区地质构造特点及噪声特性,采用有限差分法正演叠前地震记录,构建了塔里木柯东地区叠前地震记录及对应子波的训练样本集,利用地震子波、反射系数及噪声特征的区别训练生成对抗网络,实现了从叠前地震记录中有效分离地震子波.合成数据和实际地震资料处理结果表明,本文所提方法对塔里木深层超深层叠前地震子波提取具有有效性和较高的准确性,较传统方法更具优越性.     

地震子波提取方法研究进展

地震数据子波提取,是地震资料反褶积处理、波阻抗反演以及正演模拟的基础工作．准确的地震子波估计技术对于高分辨率、高信噪比、高保真度的地震勘探数据处理具有极为重要的意义．在过去的二三十年中,数字信号处理理论、非线性理论、优化理论得到了很大发展,这些为地震子波提取技术和方法注入了新的巨大活力．本文首先简要地说明了与地震子波紧密相关的褶积模型,然后对地震子波提取现状进行了概括阐述,最后给出了地震子波提取前景展望．     

能量比法提取品质因子Q（英文）

地层品质因子Q反映了地层对地震波吸收衰减的强弱,是油气检测的重要指示因子,准确提取Q值十分重要。本文根据地震子波能量衰减特征,提出基于子波衰减前后能量比的Q值提取方法。该方法是综合利用多点信息估算子波能量,规避了常规Q值方法(如质心频移法)对地震子波谱的假设,适用于任意波谱形状,但对资料的保真度要求较高。VSP正演模型测试发现,在非固有衰减(如几何扩散、反射透射损失等)得到准确补偿的前提下,能比法能较好地反演地层Q值。实际零偏VSP资料应用表明,能比法提取的Q值趋势与谱比法基本一致,具有一定的可信度。     

基于双谱幅值和相位重构的地震子波提取

利用地震记录双谱中包含子波的幅值和相位信息，以及其超强的抗噪声干扰能力，采用一种基于双谱幅值和相位重构的地震子波提取方法，首先提取出子波幅值及相位信息，进而通过傅立叶反变换，使子波得以完全恢复.本文针对双谱相位重构递推公式，提出一种新的初值选取方法，使地震子波估计的稳定性得到了提高.仿真实验证实了该方法的可行性.     

Sub‐optimal control of structures

It is well known that the classical optimal control method requires all the state variables of the controlled system to be measurable and available for control feedback. However, for a high‐order or complex system some state variables are possibly unmeasurable in practice. In addition, the control cost will be higher if more sensors are used, because it is expensive to install sensors. On the other hand, when using the optimal control method with full‐state feedback, some state variables in control feedback have only a small effect on control performance. Neglecting these state variables does not affect the control performance greatly. Good control effectiveness can be obtained by using only the state variables that have a big effect on the control performance. So the questions become how to determine those state variables which have a big effect on the control performance? and how to design the optimal controller using only the determined state variables? The discrete sub‐optimal control method with partial‐state feedback is investigated in this paper. Firstly, the continuous control system and performance index are both transformed into discrete forms. Then the state variables, which have a big effect on the control performance, are determined using the second‐order sensitivity which is the second‐order derivative of the performance index with respect to control gain. The sub‐optimal controller is finally designed using only the determined state variables. Numerical examples are worked out to demonstrate the application of the proposed control algorithm. It is shown that the relative importance of each state variable can be indicated clearly by the second‐order sensitivity. The sub‐optimal control method presented is effective in reducing maximum responses of the structure. Copyright © 2003 John Wiley & Sons, Ltd.     

Discussion on the feature of strong earthquake: Orderly distribution in time, space and intensity before the Western Kunlun Mountain Pass M=8.1 earthquake

Introduction The Western Kunlun Mountain Pass M=8.1 earthquake occurred on November 14, 2001 is the other M=8 earthquake occurred 50 years after Dangxiong, Tibet M=8.0 earthquake in Chinese mainland. The earthquake has caused the attention of the seismologists in the following aspects: 1) The fracture length is more than 400 km, which is far away from the estimated length by the statistic empirical function between the magnitude and the fracture length (WANG, et al, 2002); 2) The aftersh…     

GNSS测站坐标非线性变化影响机制的研究

对影响地球参考框架稳定度与精确度的地球动力学因素进行深入研究,能更好地促进毫米级地球参考架的建立.而研究GNSS测站坐标的非线性变化及其相关机制,是实现毫米级地球参考框架的前提,也为提升GNSS坐标精度、研究地球物理因素等提供参考.首先研究了GNSS测站坐标非线性变化的影响机制与理论改正模型,给出了季节性温度效应、地表物质负荷效应、GNSS周年性系统误差和高阶电离层延迟这四种因素的研究进展,并提出了在机制和模型研究方面一些改进的方向.然后通过以高阶电离层延迟对GNSS测站坐标时间序列的影响为例,进行分组实验,研究了高阶电离层延迟对GNSS测站坐标非线性变化的影响,并进一步将影响进行了量化.研究结果有助于对测站坐标非线性变化的机制做出更精确合理的解释,同时也有助于削弱与限制高阶电离层延迟对建立高精度地球参考框架的影响;为我国北斗地球参考框架的建立与维持提供了可靠的理论基础,具有一定的参考价值.     

Statistical distribution of surface elevation for the fourth order nonlinear random sea waves

Based upon the nonlinear model of random sea waves, the statistical distribution of wave surface elevation exact to the fourth order is derived as the truncated Gram-Charlier series,by calculating directly each order moment. The phenomenon found by Huanget al. that the agreement between observed data and investigated series deteriorates much more when the series is kept to λ₈ is explained. The effect of the approximation order on the truncation of series and the determination of coefficients is investigated. For themth order approximation, the derived series is truncated atH _3m-3 with the absence of H_3m-4, and the coefficients ofH _3m-3 andH _3m-6 are connected by a simple algebraic relation. Project supported by the National Natural Science Foundation of China.     

The Role of Naturally Occurring River Biofilms on the Degradation Kinetics of Diazinon

River biofilms are dominant riverine biota with diverse microorganisms. They have been found to contribute greatly to river self‐purification for removal of nutrients and organic matter. This study intended to investigate the ability of naturally occurring river biofilms with changing seasons for the removal of the organophosphorus pesticide diazinon. Natural river biofilms from spring showed higher ability to remove diazinon (99.9% removal) than those from winter (77%) with light exposure. In contrast to control sets without biofilms under irradiation, 27% of diazinon removal in spring and 22% in winter may result from microbial activity within biofilms. Removal of diazinon by river biofilms could be attributed mostly to degradation due to low sorption capacity of biofilms. Spring biofilms had higher dissipation rates (0.265 and 0.486 d^?1 for biofilms with different growth periods) than winter ones (0.099 and 0.119 d^?1) according to first order model. Higher ability of diazinon removal by spring biofilms may be explained by their higher bacterial and algal biomass comparing to winter biofilms. Naturally occurring river biofilms played a significant role in degradation of diazinon, particularly for those grown in spring. Their potential for use in the treatment of diazinon‐contaminated water has been demonstrated.     

频谱特性优良的高阶标定脉冲

通过理论分析研究和计算机搜寻得到几种频谱特性优良的高价标定脉冲波形，将其与我国台网广泛使用的阶跃脉冲相比较，可大幅度提高通带短周期段的标定精度，与国外使用的平衡二阶或三阶脉冲比较，具有响主尖波形特征，既可提高通带短周期段标定精度，又不降低通带长周期段精度，此外，具有生成较容易，技术难度适中，便于推广使用等特点。     

第一类算子方程的吉洪诺夫正则解的收敛性和渐近阶估计

本文对于第一类算子方程当右端近似给定和当算子与右端皆近似分别给定时,讨论如何确定正则参数。并给出吉洪诺夫正则解的收敛性和渐近阶估计。     

关于大地电磁信号非最小相位性的讨论

由于信号的功率谱仅包含振幅信息而不包含相位信息,因此传统功率谱方法仅能处理最小相位信号,难于适用于非最小相位信号．本文对不同地区的实际大地电磁(MT)信号作了分析,结果表明,不同测点MT信号在Z平面上的零点分布并不全部位于单位圆之内,可以判定MT信号一般具有非最小相位的特点,因此有必要改进传统处理方法,发展新的资料处理方式．实际信号分析,理论和数值模型实验证明,信号的高阶统计量包含其相位信息,因此,高阶统计量方法能够有效处理具有非最小相位特征的MT信号．     

On the analysis of self-similarity of earthquake sequence and its application in earthquake prediction

This paper has introduced the method of self-similarity analysis of time series into the analysis and study of earthquake sequence, and then researched its application in earthquake prediction. As parameter of earthquake time series, we can take the cumulated sum of the numbers of equivalent earthquakesQ=ΣN*, the numbers of equivalent earthquakeN*, maximum magnitudeM _max, average magnitudeQ=ΣN*, and the difference ΔN* between the numbersN* in two adjacent time intervals. The given method may be applied to analysis of long-period seismic sequences in different regions as well as to anlysis of seismic sequence in the aftershock region of strong earthquake. For making quantitative analysis the coefficient of self-similarity of earthquake sequence in order of timeμs was introduced. The results of self-similarity analysis were obtained for the earthquake sequences in North China, West South China, the Capital region of China, and for the East Yamashi region of Japan. They show that in period or half year to several years beforeM⩾7.0 andM⩾6.0 earthquakes occurred in these regions separately, the self-similarity coefficientμs calculated by using the above-mentioned parameters had remarkably anamalous decrease variations. The duration time ofμs anomaly depends on the earthquake magnitude and may be different from different regions. Therefore, the self-similarity coefficient in order of timeμs can be considered as a long-medium term precursory index. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 455–462, 1993.