RESIDUAL STATICS ESTIMATION BY STACK-POWER MAXIMIZATION IN THE FREQUENCY DOMAIN1

Traditionally, residual static corrections are based on timeshifts estimated for individual CMP sorted traces, which are later resolved into surface-consistent statics. This is a stable and attractive procedure because the data flow is simple and the memory storage required is limited. An alternative station-oriented method maximizing the stack-power estimates surface-consistent static corrections directly. The statics evaluation in this method involves several CMP gathers, which should improve the prediction of statics on noise-contaminated data. In this paper the performance of the above methods will be compared using synthetic as well as real seismic data. Neither method is capable of estimating large statics compared to the dominating period, because local optimization might fail. Global Monte Carlo search by, for instance, simulated annealing has been used to overcome the cycle-skipping problems when proper field statics are missing. Although this procedure is computationally very heavy, it may be the only way to deal with large residual statics. In order to enlarge the operational field for local optimization, it is suggested that the stack-power in the frequency domain is maximized. This makes it easy to change the frequency band during the optimization. Making use of the frequency domain will also normally be faster than the traditional time-domain optimization even for a limited number of iterations. Moreover, the main memory storage required can be significantly reduced, since it is only necessary to keep the frequency band in the memory, where the signal-to-noise ratio is good.     

任意点震源τ-P域地震图的解及AVO分析

用严格的数学推导得出τ-P域地震图的解析解。分析表明,τ-P域中地震图的子波可表示为激发震源子波的积分形式,决定反射波振幅的因素是平面波反射系数、反射界面上覆介质的波速以及方向因子。这些结果说明:1.在τ-P域进行AVO分析是可行的,并具有更高的精度;2.从一种新的途径可以进行速度函数的反演计算。     

任意点震源τ-P域地震图的解及AVO分析

用严格的数学推导得出τ-P域地震图的解析解。分析表明,τ-P域中地震图的子波可表示为激发震源子波的积分形式,决定反射波振幅的因素是平面波反射系数、反射界面上覆介质的波速以及方向因子。这些结果说明:1.在τ-P域进行AVO分析是可行的,并具有更高的精度;2.从一种新的途径可以进行速度函数的反演计算。     

烈度分布的几何特征和震源参数的估计

本文在考虑环境刚度效应和非匀阻效应的情况下,采用椭圆形震源简化模型,研究了走滑断层的地震烈度几何要素与震源参数之间的关系,初步建立了估计断层有效发震段长度、错动角、应力降和错动距离等参数的等震线法,并结合唐山、通海、炉霍和永善等震例进行了试算     

弹性体内作用力释放速度与弹性波能量

本文简要地讨论了弹性体内作用力释放速度与应变能转换为波动能量的关系。引进了粗略估算地震能量转换因子的方法。     

弹性体内作用力释放速度与弹性波能量

本文简要地讨论了弹性体内作用力释放速度与应变能转换为波动能量的关系。引进了粗略估算地震能量转换因子的方法。     

时间域全波场各向异性弹性参数反演

从各向异性弹性波的有限元正演方程出发 ,导出了反问题中时间域雅可比矩阵求解的计算公式 .它具有与时间域有限元正演方程相同的表达形式 ,故可通过有限元正演计算来获得雅可比矩阵 .研究了有限元正演算法的效率和精度、吸收边界条件等方面的问题 ,以提高反演系统的效率和精度 .在此基础上 ,实现了叠前全波场各向异性弹性参数反演 .计算表明 ,在初始模型偏离真实模型较大的情况下 ,层状模型和横向不均匀模型的反演结果均能准确地收敛到真实模型上 .     

DERIVATION OF LAYER PARAMETERS OF AN ELASTIC MEDIUM FROM REFLECTION COEFFICIENT MATRICES*

In this paper we develop a recursive algorithm to obtain the layer parameters of an elastic medium (density, P-wave velocity, S-wave velocity) from reflection coefficient matrices in terms of energy flux ratios for a non-normal incidence case. We define a layer impedance matrix, analogous to the impedance of an acoustic medium. Next we derive a matrix relationship between the layer impedance matrix of the n+ 1st layer and the reflection coefficient and parameter matrices of the nth layer. This relationship leads to recursively computing the parameters of the subsurface. We show that the elastic case—unlike the acoustic case—allows one to recover the layer parameters from the impedance matrix for non-normal incidence. The results of this work play a key role in the solution of the inverse problem with non-normal-incidence plane-wave seismic data when using a downward continuation technique.     

完整资料的地震危险性参数估计及敏感性分析

应用考虑震级不确定笥和资料完整性估计地震危险性参数的极大似然法，分别采用１９４０年和１０７０年至１９９３年完整的地震资料，计算了汾渭地震带及陕南地区的地震危险性参数。结果表明：利用近几十年来的完整地震资料结合研究区历史上发生的最大地震，可以得到较为可靠的地震危险性参数；参数敏感性分析表明，完整震级不确定性对β的影响较小；随震级不确定性的增大地震年发生率减小；在资料完整的前提下，震级下限在一定范围内     

A NOTE ON THE ESTIMATION OF THE PARAMETERS IN LOGARITHMIC STAGE-DISCHARGE RELATIONSHIPS WITH ESTIMATES OF THEIR ERROR

Abstract

Under certain assumptions the stage-discharge relationship of a channel cross-section can be approximated by a logarithmic relationship. Observational pairs of stage and discharge plotted on log-log paper often cluster around a straight line and this suggests that the assumptions involved are often approximately satisfied.

In such cases the parameters of the logarithmic relationship are usually estimated graphically from the position and slope of the straight line on the log-log paper. In this paper principles and methods are outlined for the estimation of the parameters with estimates of their standard error, via regression analysis. Because the water level of zero flows is usually one of the unknown parameters, the regression is non-linear and least squares optimal estimates can be obtained by a step-by-step approximation. The variances of the parameter estimates can be obtained from the dispersion matrix of the joint distribution of the least squares estimators via the likelihood function. An estimate of the error in predictions of the discharge depending on the corresponding stage may be obtained.     

可可托海-二台断裂断层泥的高压状态参数和动态弹性参数的测定

为了研究断层的深部构造和深部断层物质的力学性质,在国外曾有人对一些大断裂带进行过地球物理勘探,得到横跨断裂带的速度剖面和密度剖面。在物探资料的反演过程中,由于构造和物性二者均是未知的因素,取得断层物质高压状态参量的实验数据是有意义的。人     

空间域滤波在求二维重磁接触面参数中的应用

1975年、1976年格林和斯坦利发表了求二维接触面参数的一个方法。本文试图在他们工作的基础上,用空间域滤波来代替格林和斯特利用差商求水平导数和用希尔伯特变换求垂直导数的方法。文中给出了应用空间域滤波计算重、磁异常水平和垂直导数的方法。模型试验证实了理论上的推断。与差商和希尔伯特变换方法相比,优点在于它既能同时滤掉高频干扰,又能使求得的垂直导数和水平导数具有相同的精度,进而提高反演结果的精确度。     

空间域滤波在求二维重磁接触面参数中的应用

1975年、1976年格林和斯坦利发表了求二维接触面参数的一个方法。本文试图在他们工作的基础上,用空间域滤波来代替格林和斯特利用差商求水平导数和用希尔伯特变换求垂直导数的方法。文中给出了应用空间域滤波计算重、磁异常水平和垂直导数的方法。模型试验证实了理论上的推断。与差商和希尔伯特变换方法相比,优点在于它既能同时滤掉高频干扰,又能使求得的垂直导数和水平导数具有相同的精度,进而提高反演结果的精确度。     

弹性波传播数值模拟的区域分裂法

本文针对弹性波波场传播的数学模型,提出了一种基于有限元和有限差分耦合的区域分裂方法．它有灵活的网格剖分,克服了单纯用差分方法对区域的依赖性,可以适用于曲边地表;达到同样精度所需的计算量比有限元方法小;并易于实现并行计算．数值实验表明了算法的有效性．     

ldquo;区域-时间-长度rdquo;算法中特征参数的估计及应用

根据地震前震源及周围地区出现的空区的时空特征, 提出了一种估计ldquo;区域-时间-长度rdquo;算法中特征参数（特征距离和特征时间）的方法, 并介绍了2006年一些学者提出的用相关系数估计特征参数的方法. 用这两种方法研究了近年来发生在中国大陆西北和西南地区的4次中强地震前的地震活动异常特征. 结果表明, 本文提出的估计特征参数的方法是一种具有物理意义、 使用简单的方法, 对中国大陆西北和西南地区的4次中强震的应用都有较好的效果.     

ESTIMATION OF REFLECTOR PARAMETERS BY THE VIRTUAL IMAGE TECHNIQUE*

The seismic interpretation process generally exploits three of the following independent basic assumptions:

• 1 Input quantities are obtained by simplification of measured data (travel time curves).
• 2 2. The geological model contains only a few parameters (for example, plane interfaces and constant interval velocities).
• 3 3. Approximate transformations may be applied.

The first two are related to the simplification of the phenomena and enhance their essential features. The transformation which establishes relations between simplified data and model is required to be unique, stable, and sufficiently accurate. Practically, the travel time curves are almost exclusively regarded as hyperbolas. We also accept this approximation. The paper presents a simple recursive algorithm for the evaluation of the depth and dip of plane reflectors and the interval velocities. It is a simple fact, that there exists a unique relationship between three hyperbolic parameters and a homogeneous dipping layer. Accordingly, two layers can be replaced by a single layer and the parameters of the lower boundary can be estimated when the upper one is known, initiating virtual shotpoints and geophone points (virtual surface). So, the case of multilayered media can be reduced in sequential steps to the case of a single homogeneous layer using a stripping type procedure. Some synthetic model examples are provided to demonstrate the abilities of the algorithm.     

EFFECTS OF FOREST ON THE SNOW PARAMETERS DERIVED FROM MICROWAVE MEASUREMENTS DURING THE BOREAS WINTER FIELD CAMPAIGN

Passive microwave data have been used to infer the areal snow water equivalent (SWE) with some success. However, the accuracy of these retrieved SWE values have not been well determined for heterogeneous vegetated regions. The Boreal Ecosystem–Atmosphere Study (BOREAS) Winter Field Campaign (WFC), which took place in February 1994, provided the opportunity to study in detail the effects of boreal forests on snow parameter retrievals. Preliminary results reconfirmed the relationship between microwave brightness temperature and snow water equivalent. The pronounced effect of forest cover on SWE retrieval was studied. A modified vegetation mixing algorithm is proposed to account for the forest cover. The relationship between the microwave signature and observed snowpack parameters matches results from this model.     

ELASTIC PARAMETER ESTIMATION BY COHERENCY OPTIMIZATION1

We present a method for estimating P- and S-velocities within defined layers (macromodel), using only kinematic properties (i.e. traveltimes) of the wavefield. The method does not require identification of mixed-mode events on prestack or post-stack data. After obtaining a V_p-depth model by coherency inversion, S-velocities are determined by coherency optimization along computed traveltime curves for mixed-mode events on prestack data. Since the method does not involve any dynamic wavefield computations, a simple ray-tracing algorithm is used to solve the forward problem. The simplicity of the scheme, together with the ability to apply it locally, makes it highly suitable for interactive use. Results of this method may be used to detect Poisson's ratio anomalies within or between layers and may serve as an initial model for more complicated elastic inversion algorithms.     

ON THE CONSTRUCTION OF THE 3D BAND-LIMITED EXTRAPOLATION OPERATOR IN THE SPACE-FREQUENCY DOMAIN1

Based on an expansion of the band-limited 3D extrapolation operator in terms of orthogonal Chebyshev polynomials, a closed form expression of the space-frequency response is presented. A key step is an evaluation of the (inverse) 2D Fourier transform of circularly symmetric functions, which is related to the (zero-order) Hankel transform. Hankel transforms of individual members of the orthogonal set of polynomials are available from tables and summation of series; hence, the real and the imaginary parts of the space-frequency response can be found in terms of cylindrical and spherical Bessel functions, respectively. The procedure permits an efficient and accurate evaluation of the space-frequency response.     

THE GRAVITY AND MAGNETIC FIELDS FROM ELLIPSOIDAL BODIES IN THE WAVENUMBER DOMAIN*

Wavenumber domain expressions for bodies with elliptical cross-section and of ellipsoidal shape have been developed both for homogeneous bodies and for certain bodies of density/magnetization varying linearly with depth or, more generally, according to a polynomial with depth. The simple expressions thus obtained lend themselves to an easy analysis, especially for long and short wavelengths. At the long-wavelength end of the spectra their decay is governed by an exponential with a decay “depth” equal to the depth to the center of mass. At the short-wavelength end this depth is replaced by the depth to the upper focus of the ellipsoid (or the elliptic cross-section). For vertically inhomogeneous ellipsoids the decay rate is also dependent on the product of the vertical gradient of density/magnetization and their semi-axes.