数据域初至波走时与成像域反射波走时联合层析速度建模方法

复杂地表探区,尤其是盆山过渡区的油气勘探是我国也是世界上油气勘探的重点区域,但是此类区域油气地震勘探中满足精确地震成像的速度建模一直是个没有很好解决的问题.本文提出了一种综合性的数据域初至波走时与成像域反射波走时联合层析复杂地表浅中深层速度建模方法,并针对联合层析速度反演解的非唯一性问题,深入地分析了层析反演中正则化的本质意义,指出了建立构造特征正则化方法的具体技术路线,提出了联合层析的实现流程及策略.理论和实际数据试验表明,本文提出的数据域初至走时与成像域反射走时联合层析浅中深层速度建模技术避免了常规建模方法中浅层速度模型与中深层速度模型的融合问题,较好地解决了传统成像域反射层析对近地表模型的不可控更新问题,整体提升了深度域浅中深层速度模型的建模精度,进而提高了复杂地表、复杂构造区的地震成像质量.     

频率域吊舱式直升机航空电磁资料的马奎特反演

频率域吊舱式航空电磁系统在国内尚处于研究和试生产阶段,由于缺少有效的数据处理手段,限制了该项技术的进一步应用和发展.本文通过对马奎特方法原理介绍,成功地将其运用到频率域航空电磁资料的反演计算中,并对几个关键技术——雅可比矩阵计算、初始模型赋值、形态模型与物性模型反演效果等进行分析,提出了切实可行的算法,并在计算机上加以实现.最后,通过理论模型和实测数据测试验证了算法的有效性和正确性,填补了国内该应用领域的技术空白,取得了较好的应用效果.     

自然时间域中的地震序列参数分析

自然时间χ是Varotsos等于2001年提出的一种新的时间域, 其将复杂系统的时间序列在自然时间域中进行分析,能够有效地提取有用信号并提高相关结果的准确性,从而更容易获得复杂系统的动态特征.文中对自然时间法进行了简单介绍,选取中国地震台网中心1978—2014年地震目录中震级排序前30的震例,计算每次地震的归一化能量在自然时间域中的方差κ₁及其变异系数β,并将方差κ₁作为序列参数,利用变异系数β对序列参数κ₁进行定性分析,并在此基础上,对序列参数κ₁进行定量分析.研究结果表明:30次震例中有21次震例的地震序列参数κ₁自震前半小时至几个月开始持续在0.07上下波动,并在主震发生前迅速下降至0值附近.此外,还简单讨论了定量分析中时间窗口的选择以及分析结果中可能出现的特殊情况.本文的研究结果对我国地震事件的回溯性研究及地震预测研究具有一定的指导意义.      

基于地震波叠加模式的空间域划分及质点运动空间差异——以SV波入射为例

针对地震动空间差异问题,以半无限空间内平面SV波入射为例,采用波动理论和叠加原理相结合的方法研究地震动的空间特征。首先,分析入射波和反射波在空间内形成质点运动的叠加模式差异,并依此对空间域进行划分;其次,针对不同泊松比和SV波入射角情形研究叠加区与分离区的分界线控制情况;最后,对比分析不同空间域内的质点运动在峰值、持时等方面的特征。研究结果显示:当SV波入射时,叠加区与分离区的分界线通常由z₃ （反射P波与反射SV波的分离线）控制;同时存在两种特殊情况,当SV波垂直入射时,分界线由z₁ （入射SV波与反射SV波的分离线）控制,当反射SV波幅值为零时,分界线由z₂ （入射SV波与反射P波的分离线）控制。在入射波和反射波的影响下,质点运动时程的形状具有水平不变性。三波贡献时段只出现在深度小于z₁的质点的运动时程中,且持时随着深度的增加线性减少;双波贡献时段出现在位于叠加区内的质点的运动时程中,持时沿深度先增加后减少;单波贡献时段随着深度的增加而逐渐加长,在分离区达到最大值。质点运动总持时随深度逐渐增加,在分离线z₂和z₃深度处存在两个拐点。在质点运动峰值方面,靠近自由面的叠加区质点运动峰值变化较大,深度较大的叠加区和分离区的质点运动峰值一般不变。      

Characteristics and dynamic settings of the Central-east Asia multi-energy minerals metallogenetic domain

That more than 82 percent of proved sandstone-type uranium deposits coexist with proved oil-gas or coalfields in the world reflects the fact of coexistence and accumulation of multi-energy minerals including oil, gas, coal and uranium in the same basin. Especially, this phenomenon is most typical in the Central-east Asia energy basins. Across China, Mongolia and some central Asian countries, the giant Central-east Asia metallogenetic domain (CEAMD) stretches more than 6,000 km from Songliao Basin of China in the east to the Caspian Sea in the west. The multi-energy minerals distribution characteristics of the domain include: their spatial distribution is complicated and ordered; the ore-bearing horizon relates closely to the geographical region; the accumulation/mineralization and localization time is the same or close; the occurrence setting and accumulation/mineralization have close correlation; and they have rich provenance for all the minerals. All of these imply that they have close relations between each other under a unified geodynamic background. The exogenetic uranium mineralization process in CEAMD can be divided into five phases using time limits of 100 Ma, (50±2) Ma, 20±(2–4) Ma, 8–5 Ma. The major mineralization periods and their differences in each primary uranium-bearing basin are identical to the oil-gas accumulation and localization periods and phases in the same basin, and are also in response to regional tectonics and controlled in general by the regional geodynamic environment. For industrial application and commercial exploitation, it is suggested that an important period for coexistence, accumulation and localization of oil, gas, coal and uranium and their interaction mainly occur in the late/last and post basin evolution. Through generalized analysis and comparison of accumulation/mineralization environment of the energy basins in CEAMD, the authors propose that the relatively stable regional tectonic background and moderate (weaker) structural deformation probably are necessary for formation, coexistence and preservation of large and medium-scaled sandstone-type uranium ore deposits, oil-gas fields and coalfields, while basins in favor of coexistence and accumulation are those intracratonal, intermediary massif basins and corresponding reformed basins.     

Higher-order statistics correlation stacking for DC electrical data in the wavelet domain

DC (direct current) electrical and shallow seismic methods are indispensable to the near surface geophysical exploration, but the near surface areas are very difficult environments for any geophysical exploration due to the random noise caused by near surface inhomogeneities. As a new algorithm based on higher-order statistics theory, the higher-order correlation stacking algorithm for seismic data smoothing in the wavelet domain has been developed and applied efficiently to filter some correlation noise that the conventional second-order correlation stacking could not inhibit. In this paper, this higher-order statistics correlation stacking technology is presented for DC electrical data in wavelet domain. Taking into account the single section and multiple section data, we present two new formulations of correlation stacking for DC electrical data. Synthetic examples with Gaussian noise are designed to analyze the overall efficiency of the new algorithm and to determine its efficacy. Meanwhile, comparison with the traditional least-squares optimization inversion method for field examples from electrical imaging surveys and time-domain IP measurement in China shows its significant advantages. The quality of the new algorithm also has been assessed by physical simulation experiments. This new technology in DC electrical exploration measurements provides a new application in engineering and mining investigation.     

Thermal relaxation of magnetic domain misalignment in rocks

Summary The anisotropy of susceptibility which is induced in rocks and dispersed powdered magnetite by the application of a strong alternating field is removed by heating more rapidly than is thermoremanence in the same specimens. The anisotropy associated with thermoremanence induced in the earth's field is negligible, but in fields greater than 5 oersteds it becomes appreciable. It is concluded that the domain structure associated with low field thermoremanence is only a very slight perturbation of the zero field structure. However this is much less simple than has been supposed and involves two- or three-dimensional domain closure. An appropriate minor revision of the theory of multidomain thermoremanence is presented.     

无人机频率域半航空电磁法三维反演

当前无人机频率域半航空电磁方法(SAEM)成为地球物理勘探中的新兴技术,该方法通过空中无人飞行器测量地面上单个或多个可控源的垂直磁场.本文为无人机频率域SAEM开发了三维反演程序,正演采用交错网格有限差分.由于无人机采集的数据量巨大,因此使用了有限内存拟牛顿法(LBFGS)实现快速的三维反演,以避免计算和存储巨大的灵敏度矩阵.为了提升无人机频率域SAEM的三维反演效果,本文进一步实现了无人机频率域SAEM与大地电磁(MT)的三维联合反演,并对联合反演实施了地震结构约束,结构约束采用交叉梯度法实现.MT可以增加勘探深度,而结构约束可以提高电磁法反演的分辨率.最后通过建立四个理论模型,证明了本文程序的有效性.     

基于Chebyshev多项式的非对称走时Kirchhoff叠前时间偏移角道集求取

地震射线走时的求取方法是叠前时间偏移研究的核心问题之一,也是影响计算时间域角道集角度精确性的关键因素之一.本文基于Kirchhoff叠前时间偏移,应用第一类切比雪夫多项式,对弯曲射线对称走时加以改进,引进非对称项,优化后得到切比雪夫非对称走时方程,与高精度走时进行比较和误差分析,再将该走时求取方法应用于时间域角道集的求取中,得到地下较真实的入射角.通过模型计算和实际地震资料处理证明,此种非对称走时及其角道集的求取方法具有精度高、计算量少的优点.     

半径-斜率域加权反假频地震数据重建

为减小地震数据缺失给地震后续处理工作带来的影响,需要对地震数据进行插值重建.针对反假频插值重建这个难点问题,进行了相关研究,并由此提出了一种改进的R-P（半径-斜率）域加权反假频地震数据插值重建方法.该方法将F-K（频率-波数）谱变换到R-P域,在R-P域设计一个权函数并将其作用于每次的迭代插值过程.通过模型数据和实际数据的测试,证明了该方法具有较好的反假频插值重建能力.     

Time domain dynamic analysis of piles under impact loading

In this paper, time domain dynamic analysis of piles under impact loading is presented. For this purpose a hybrid boundary element technique is implemented. Linear beam column finite elements are used to model the piles and resulting governing equations are solved using an implicit integration scheme. The continuum is assumed to be elastic and an efficient step-by-step time integration scheme is implemented by using an approximate half space integral formulation. By enforcing displacement equilibrium conditions at each time step, a system of equations is generated which yields the solution. Results of this time domain formulation under linear material behavior are compared with Laplace domain results to validate the methods.     

平面波域反数据处理压制多次波方法研究

在地震勘探领域,尤其是海洋地震勘探中,多次波一直是影响地震处理与解释的主要因素之一.本文基于x-t域的反馈模型及多次波衰减的理论,详尽推导了x-t域反数据处理的方法;基于平面波域多次波的产生机制,借鉴x-t域反数据处理的方法,推导出在平面波域进行反数据处理的原理.文中给出一个有限差分的模拟数据进行测试,处理结果表明,本方法可以有效地衰减表层相关多次波,提高地震数据分析的精确性,在保护了一次波能量的同时,可以更加有效快捷地去除多次波.     

角度域剩余深度对剩余速度的敏感性分析

本文针对地震勘探深度域偏移速度建模研究,利用角度域共成像点道集(ADCIGS)建立了以剩余速度为自变量,剩余深度为目标函数的关系式,及目标函数的梯度公式.利用导出的两个公式分别对剩余深度与剩余速度的关系进行了定量分析.通过理论分析和模型试算证明初始速度模型的误差具有方向敏感性,即正误差较负误差对速度建模迭代收敛更敏感.利用此结论进行深度域速度建模既可以提高计算效率也可以提高建模精度.     

An operational modal analysis method in frequency and spatial domain

A frequency and spatial domain decomposition method （FSDD） for operational modal analysis （OMA） is presented in this paper, which is an extension of the complex mode indicator function （CMIF） method for experimental modal analysis （EMA）. The theoretical background of the FSDD method is clarified, Singular value decomposition is adopted to separate the signal space from the noise space. Finally, an enhanced power spectrum density （PSD） is proposed to obtain more accurate modal parameters by curve fitting in the frequency domain. Moreover, a simulation case and an application case are used to validate this method.     

Statistical moment-based structural damage detection method in time domain

A novel structural damage detection method with a new damage index,i.e.,the statistical moment-based damage detection(SMBDD) method in the frequency domain,has been recently proposed.The aim of this study is to extend the SMBDD method in the frequency domain to the time domain for building structures subjected to non-Gaussian and non-stationary excitations.The applicability and effectiveness of the SMBDD method in the time domainis verified both numerically and experimentally.Shear buildings with various damage scenarios are first numerically investigated in the time domain taking into account the effect of measurement noise.The applicability of the proposed method in the time domain to building structures subjected to non-Gaussian and non-stationary excitations is then experimentally investigated through a series of shaking table tests,in which two three-story shear building models with four damage scenarios aretested.The identified damage locations and severities are then compared with the preset values.The comparative results are found to be satisfactory,and the SMBDD method is shown to be feasible and effective for building structures subjected to non-Gaussian and non-stationary excitations.     

基于高斯束传播算子的成像域走时层析成像方法

层析反演是速度建模中最重要的方法之一,结合偏移成像在成像域进行走时层析速度反演是当前比较成熟有效且广泛应用的技术.本文从高斯束偏移成像条件出发,在波动方程的一阶Born近似和Rytov近似下,推导了成像域走时扰动与速度扰动的线性关系,建立了成像域走时层析方程及其显式表达的层析核函数.该核函数的本质是有限频层析核函数,利用该核函数替换常规射线层析核函数可以明显提高层析反演精度.该核函数的计算关键是背景波场格林函数的计算,本文利用高斯束传播算子计算格林函数进而得到走时层析核函数,实现方式灵活高效且计算精度较高.基于高斯束传播算子的偏移成像与层析成像相结合进行深度域建模迭代,体现了速度建模与偏移成像一体化的思想.数值计算及实际数据应用证明了基于高斯束传播算子的成像域走时层析方法的有效性.     

2D共炮时间域高斯波束偏移

针对传统射线方法在奇异区成像精度不高,而2D频率域高斯波束叠前深度偏移需要计算成像点处每个频率的格林函数,影响计算效率的问题,本文通过使用复走时代替实走时,改变频率域下成像公式的积分顺序,给出了在时间域下进行高斯波束偏移的方法和计算公式.本文使用复杂数值模型验证了2D时间域高斯波束叠前偏移方法的正确性,并同传统射线偏移成像结果做了对比.对比结果表明时间域高斯波束偏移在成像精度上优于传统射线偏移.     

虚拟波动域三维海洋可控源电磁场正演模拟

本文基于对应原理将似稳态条件下频率域电磁场扩散方程转换成虚拟波动域电磁场波动方程,采用高阶时域有限差分进行求解,引入复频移完全匹配层吸收边界条件,降低了内存需求,提高了计算效率,并在虚拟波动域用伪δ函数离散电偶极源,实现了虚拟波动域任意取向电偶极源三维海洋可控源电磁场高阶时域有限差分正演算法.通过与拟解析解和频率域三维可控源电磁场数值模拟结果的对比,验证了本文算法的正确性和高效性,且探讨了网格参数和边界条件对不同频率电磁场模拟结果的影响.     

System parameters of soil foundations for time domain dynamic analysis

Soil-structure interaction analysis is usually carried out in the frequency domain, because the compliance functions of the half-space are known only in the frequency domain. Since non-linear analysis cannot be carried out in the frequency domain, a system with frequency independent parameters is used to represent the half-space soil medium so that a nonlinear analysis in the time domain becomes possible. The objective of this paper is to propose a system with lumped parameters, which are independent of frequency, to represent the half-space soil medium. The proposed frequency independent system consists of a number of real discrete structure elements; thus the existing dynamic analysis programs may be adoptable with little modification. In this paper, the parameters are found by minimizing the sum of the squares of deviations between the steady-state responses of the theoretical half-space model and those of the lumped parameter system over a specified frequency range. Once the parameters have been found, the lumped parameter system can be used in practical applications for time domain dynamic analysis of either linear or non-linear structures. In comparison with the dynamic response of the theoretical half-space model, the lumped parameter system yields satisfactory results.     

Modeling seismic wave propagation in heterogeneous medium using overlap domain pseudospectral method

Pseudospectral method is an efficient and high accuracy numerical method for simulating seismic wave propaga- tion in heterogeneous earth medium. Since its derivative operator is global, this method is commonly considered not suitable for parallel computation. In this paper, we introduce the parallel overlap domain decomposition scheme and give a parallel pseudospectral method implemented on distributed memory PC cluster system for modeling seismic wave propagation in heterogeneous medium. In this parallel method, the medium is decomposed into several subdomains and the wave equations are solved in each subdomain simultaneously. The solutions in each subdomain are connected through the transferring at the overlapped region. Using 2D models, we compared the parallel and traditional pseudospectral method, analyzed the accuracy of the parallel method. The results show that the parallel method can efficiently reduce computation time for the same accuracy as the traditional method. This method could be applied to large scale modeling of seismic wave propagation in 3D heterogeneous medium.