黏弹性介质VSP记录模拟及在估算Q值研究中应用

采用标准线性固体模型,本文建立了黏弹性介质完全匹配层吸收边界的高阶速度-应力交错网格有限差分算法,并对黏弹性介质中的地震波传播进行了数值模拟.基于黏弹性波动方程正演模拟提供的零偏VSP全波场数据,本文进行了质心频移法计算Q值的反演分析.结果表明,反射波、转换波及短程多次波对频谱的影响较大,对Q值反演造成一定误差.本文的结论为实际零偏VSP资料估算地层Q值提供了有益的指导.     

远震相对走时数据快速计算方法及应用

远震层析成像技术已成为研究地球深部速度结构最为主要的方法,而其所用数据通常为初至震相的相对走时残差值.本文针对信噪比差的远震波形资料提出一种计算远震相对走时残差数据的快速方法,整个计算过程全部由计算机自动完成.该方法主要有两大特点:(1)利用互相关方法计算波形间的偏移时间时引入波形相位信息,有效压制噪声,增强有用震相的识别;(2)改进常规方法中计算相对走时残差的理论公式,避免求解超定方程组,提高计算精度.为验证新方法的可行性和实用性,以长江中下游地区远震波形资料为例,采用常规方法和新方法分别计算相对走时残差数据,对比结果显示:新方法比常规方法的工作效率和数据精度都高.     

A new method for laboratory estimation of the transverse dispersion coefficient

We introduce a method for identifying the transverse dispersion coefficient in laboratory experiments based on the analytical solution of a pulse injection of a nonreactive solute in a soil column (cylindrical geometry) packed with a homogeneous porous medium. This method takes into account the effect of boundary conditions such as no flux on the column perimeter, and it does not need a priori knowledge of the longitudinal dispersion coefficient. Numerical applications of the method show that it is stable and robust and that the results are reasonably in accordance with those found using the classical maximum likelihood method.     

稳定正则化参数估计方法及其在盆地基底重力异常反演中的应用

正则化方法通过带有正则化参数的约束项,将不适定问题转换为一个适定问题.如何选取最优正则化参数一直以来都是正则化研究的难点和热点.本文通过定义解的不稳定性度量来直接估算正则化参数μ的最优值,并将这种正则化参数估计方法应用到二维沉积盆地基底重力反演中.测试该方法在通过对一次野外测量的数据加不同噪声得到的多组数据与多次野外测量中得到的多组数据这两种情况中的反演效果.最后将该方法应用到非洲西海岸的北加蓬次盆进行盆地基底反演,测试该方法的实用性.模型测试的结果显示,在这两种情况下获得的反演解非常接近且能够反演得到较为准确的模型基底深度,故该方法适用于一般情况下只进行一次野外测量的实际重力勘探情况且能得到稳定的最优反演解;实际资料的最优反演结果稳定且符合当地的地质构造背景.在模型测试与实际资料测试中,都能够确定最优正则化参数并得到最优反演结果,证明了该方法在重力反演中的正确性和实用性.

     

A new inverse method and application to ocean data

A new method is proposed to inverse normalization data of hidden variables in a dynamical system by embedding a time series in multidimensional spaces and applying a normalization analysis to the conditional probability density of points in the reconstructed phase spaces. The method is robust in the application to Lorenz system and 4-dimensional R?ssler system by testing quantitatively and qualitatively the correlation coefficient between inverse data and original data in time domain and in frequency domain, respectively. By applying the method to analyzing the South China Sea data, the normalization data of wind speed is extracted from the sea surface temperature time series.     

高分辨折射地震资料处理方法及其应用

高分辨折射探测剖面近几年在我国的一些重要地学基础研究项目，特别是在中国地震局“十五” 期间开展的城市活断层探测及复杂上部地壳精细结构研究中得到了越来越广泛的应用.本文对在用传统有限差分方法处理高分辨折射地震资料时的缺陷及其改进算法的研究进展进行了较全面的讨论，对一些缺陷我们已给出了解决的方案，并已成功地应用于实际人工地震高分辨折射测量资料的分析处理，取得了较好的效果，还给出了将改进方法应用于深反射剖面初至波处理解释的一个应用实例，对于另一些缺陷我们在对国内外该领域研究现状调研的基础上，给出了目前我们正在进行中的解决方案.     

利用核磁共振测井资料构造储层毛管压力曲线的新方法及其应用

By analyzing hundreds of capillary pressure curves, the controlling factors of shape and type of capillary pressure curves are found and a novel method is presented to construct capillary pressure curves by using reservoir permeability and a synthesized index. The accuracy of this new method is verified by mercury-injection experiments. Considering the limited quantity of capillary pressure data, a new method is developed to extract the Swanson parameter from the NMR T2 distribution and estimate reservoir permeability. Integrating with NMR total porosity, reservoir capillary pressure curves can be constructed to evaluate reservoir pore structure in the intervals with NMR log data. An in-situ example of evaluating reservoir pore structure using the capillary pressure curves by this new method is presented. The result shows that it accurately detects the change in reservoir pore structure as a function of depth.     

A method for the interpolation of nonnegative functions with an application to contaminant load estimation

The objective of this work is to extend kriging, a geostatistical interpolation method, to honor parameter nonnegativity. The new method uses a prior probability distribution based on reflected Brownian motion that enforces this constraint. The work presented in this paper focuses on interpolation problems where the unknown is a function of a single variable (e.g. time), and is developed both for the case with and without measurement error in the available data. The algorithms presented for conditional simulations are computationally efficient, particularly in the case with no measurement error. We present an application to the interpolation of dissolved arsenic concentration data from the North Fork of the Humboldt River, Nevada.     

基于脉冲频响函数的MATLAB动力方程求解方法

提出一种基于脉冲频响函数并利用MATLAB求解的方法，由于脉冲频响函数利用卷积公式进行动力微分方法计算，因此，从理论上讲，它适合于任意外力下的动力方程求解，同时，MATAL又提供了卷积函数conv，所以，在MATLAB下求解动力方程将变得十分容易。     

The R-approximation method and its application to the interpretation of detailed gravity and magnetic data

The application of the R-approximation method based on the use of the Radon integral transform within the framework of the method of linear integral representations to the interpretation of detailed gravity and magnetic data is considered in this paper. The results are presented for some research areas located in Russia and in the Crimea (Ukraine). The method determines the distribution of anomalous field elements, construction of the analytical continuation of fields, and their linear transformations with a sufficiently high degree of accuracy.     

The numerical method of Fourier eigen transform and its application in seismicity analysis

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Successive formula method for numerical analysis of vibrating response

The algorithm of successive formulas for computing numerical vibrating response of unequal time interval for a single-degree of freedom oscillator in linear cases are more systematically introduced in the paper. Some numerical analysis characteristics of the algorithm are discussed. It is proved that the algorithm is unconditionally stable and convergent. A computer program for simultaneous calculation of the relative displacement, the relative velocity and the absolute acceleration response spectra is edited in the paper. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 236–242, 1992.     

A model for heat and water balance estimation and its application to land use and climate variation

This paper presents a method, which has been recently developed in the Department of Agrometeorology of the Poznań Agricultural University, for estimating heat balance components based on standard meteorological data, plant development stage, and land-use conditions. Estimates of latent heat flux components made it possible to obtain values of areal evapotranspiration and surface runoff. The method was applied in four catchment areas in Central Poland under present climatic conditions as well as under new, expected climatic conditions caused by an increase of ‘greenhouse gases’ in the atmosphere. Some changes in land use were also considered. The results show significant changes in the water balance when comparing present and future conditions of precipitation and evapotranspiration.     

Newmark精细积分格式及其在地震反应分析中的应用

在Newmark精细直接积分法的基础上,应用高斯积分与精细指数运算,提出该方法的两种逐步积分格式。文中对两种积分格式的稳定性和精度进行了分析。经过分析比较,第1种逐步积分格式计算精度较高,其稳定性明显地满足算法稳定性分析的条件;而第2种积分格式计算精度相对较差,且是不稳定的。因此本文将第1种积分格式应用于结构的地震反应分析中。算例表明,该逐步积分格式对地震作用有很好的适应性。     

A numerical laboratory for simulation and visualization of seismic wavefields1

Computational seismic modelling (CSM) plays an important role in the geophysical industry as an established aid to seismic interpreters. Numerical solution of the elastic wave equations has proved to be a very important tool for geophysicists in both forward modelling and migration. Among the techniques generally used in CSM, we consider the finite-element method (FEM) and investigate its computational and visualization requirements. The CSMFEM program, designed for this purpose and developed on an IBM 3090 computer with vector facility, is described in detail. It constitutes a numerical laboratory for performing computer experiments. Two Newmark type algorithms for time integration are compared with other time integration schemes, and both direct and iterative methods for solving the corresponding large sparse system of linear algebraic equations are analysed. Several numerical experiments to simulate seismic energy propagation through heterogeneous media are performed. Synthetics in the form of common shot gathers, vertical seismic profiles and snapshots are suitably displayed, since with the large amounts of data obtained from CSM research, methods for visualization of the computed results must be developed. The FEM is compared with other numerical tools, such as finite-difference and pseudo-spectral methods.     

Variational data assimilation for parameter estimation: application to a simple morphodynamic model

Data assimilation is a sophisticated mathematical technique for combining observational data with model predictions to produce state and parameter estimates that most accurately approximate the current and future states of the true system. The technique is commonly used in atmospheric and oceanic modelling, combining empirical observations with model predictions to produce more accurate and well-calibrated forecasts. Here, we consider a novel application within a coastal environment and describe how the method can also be used to deliver improved estimates of uncertain morphodynamic model parameters. This is achieved using a technique known as state augmentation. Earlier applications of state augmentation have typically employed the 4D-Var, Kalman filter or ensemble Kalman filter assimilation schemes. Our new method is based on a computationally inexpensive 3D-Var scheme, where the specification of the error covariance matrices is crucial for success. A simple 1D model of bed-form propagation is used to demonstrate the method. The scheme is capable of recovering near-perfect parameter values and, therefore, improves the capability of our model to predict future bathymetry. Such positive results suggest the potential for application to more complex morphodynamic models.     

基于谱元法的全波形反演及其在海底地震数据中的应用

全波形反演已被广泛应用于获取地下速度结构.而反演问题与正演方法密切联系,针对特定反演问题,合适的正演方法能极大提高反演效率和精度.本文首先验证谱元法在含起伏界面模型数值模拟方面的优势,在此基础上将谱元法作为正演引擎应用于全波形反演,并为克服未知子波的影响,采用一种归一化的频率域目标泛函.结果表明,起伏地表情况下,基于谱元法的全波形反演相比于基于传统有限差分法反演,具有更高的反演精度.进一步,本文将基于谱元法的波形反演方法应用于OBS观测系统的理论合成数据和野外采集数据.谱元法非结构化网格剖分自然满足自由边界条件,能很好地适应不规则海床并模拟多次波.理论实验表明,即使在OBS观测系统很稀疏的情况下,基于谱元法的全波形反演仍能获得海底以下正确的高波数速度结构.在处理实际OBS数据时,本文采用分频策略以减少反演非线性,初始模型成功更新,其结果揭示了西沙海槽海底以下更多的细节信息.

     

确定震源深度的PTD方法及其应用

根据对不同台站间初至到时作变换后的时差来计算地震的深度，利用该方法计算了华东地区１８２￣１９９２年底能定出深度的地震，并作了相应的误差分析，按中国分区速度结构，编制出各区的深度－走时差表，并举例说明该表的用法。