利用多分量地震数据消除散射面波

引言在许多探区,浅层通常具有很强的非均匀性。这种非均匀性能够产生散射面波。当这些散射波掩盖住了来自地下深部的体波反射时就会降低地震数据的质量。靠近接收线散射的面波(纵测线方向的散射波)可用通用的滤波技术加以消除(Yilmaz,1987)。但远离接收线散射的面波(横测线方向散射波)却是滤波所无法完全消除的,因为这些波类似于体波反射。在以前的论文中,我们已经用模拟数据(Blonk和Herman,1994)和野外数据(Blonk等,1995)探讨过消除散射面波的反向散射法。目前,我们把注意力集中在质点速度的垂向分量上,这就意味着面波和体波反射可以根据相应的相位速度差异加以识别。

基于深度学习的地震散射面波智能压制方法

塔里木沙漠区地表为复杂的黄土和沙漠,非均质性较强,面波传播到非均质散射体时会激发散射面波.常规的面波压制方法是利用面波和有效波在能量、频率和视速度上特征区别来设计滤波器,在变换域下压制面波.然而,散射面波与有效波的特征混淆在一起,无法通过常规滤波方法去除.针对塔里木沙漠区散射面波干扰的实际问题,本文提出一种深度学习方法来进行压制,提高叠前数据信噪比.首先,在合成速度模型和实际速度模型上利用弹性波方程正演模拟出散射面波,构造深度学习训练集,验证深度学习方法在散射面波压制上的可行性;然后,利用工业方法处理野外数据来构造实际训练集,在合成数据训练网络的基础上进行参数微调和网络迁移.数值实验表明,使用迁移学习方法能够利用较少的训练样本实现与大量训练样本类似的效果.

基于地震干涉法的可控震源黑三角噪声压制技术及应用

沙漠区可控震源资料通常存在严重的高能量黑三角噪声,应用常规的转换域滤波或基于Born近似的迭代反演预测-消除方法进行去噪时,效果不理想。利用新疆某工区可控震源资料,定性分析了黑三角噪声的形成机理,主要由散射面波和可控震源与地表之间的谐振形成。针对黑三角区内的散射面波消除问题,基于炮-检地震干涉及模式的匹配相减方法,研发了可控震源散射面波干涉预测与匹配相减技术,其特点是实测地震资料驱动,无需速度模型;同时,将该技术与用于压制如谐振等不规则强噪声的异常噪声压制技术相结合,形成了可控震源黑三角综合去噪方法技术。以新疆某工区可控震源地震资料为测试资料,对比了该综合去噪技术与某商业软件的应用结果,表明该综合去噪技术能有效消除黑三角区内的强能量噪声,尤其是有效压制了散射面波,显著改善了叠前时间偏移结果,进而恢复地层真实反射特征,断裂和断溶体成像效果优于某商业软件。

FINITE ELEMENT-ARTIFICIAL TRANSMITTING BOUNDARY METHOD FOR WAVE SCATTERING FROM IRREGULAR CYLINDER

The finite element artificial transmitting boundary method is employed here to treat the near field scattering of a cylindrical wave from an irregular cylinder. A comparison is made between this method and the analytical one. And then examples are given to demonstrate the solution of several problems of the irregular object scattering. The method can not only produce clear physical pictures, but can efficiently handle many complicated scattering problems.

“黑三角”噪声特征分析及压制

陆上地震勘探可控震源采集的单炮道集中,“黑三角”噪声在三维情形下分布于以炮点位置为顶点的锥形体内,其特征复杂且多变,因而严重降低了地震数据的信噪比和成像结果的质量。为此,首先分析了以瑞雷型面波及其强散射波为主的“黑三角”噪声特征,提出了“黑三角”噪声压制方案,发展出了数据自适应压制方法。关键步骤包括:显式或隐式地划分出“黑三角”噪声区域,基于划分区域的最大视速度对数据进行线性动校正(LMO),对数据局部取窗(时间空间窗),分频进行稳健主成分分析(robust principal component analysis,RPCA)以提取线性信号,利用统计滤波器消除异常幅值噪声。实际数据的处理结果表明,该技术方案可以较好地压制面波,保留有效信号。

Characterization and Modeling of Finite-Ground Coplanar Waveguides in 0.13μm CMOS

We discuss the characterization and modeling of coplanar waveguides （CPW） realized in TSMC 0. 13μm CMOS process. EM-field simulations with momentum are performed to estimate the important parameters of the transmission lines, such as characteristic impedance and propagation loss. Coplanar waveguide libraries are designed with Z values of 30,50,70, and 100Ω. Finally, the propagation constant and the characteristic impedance are measured in a frequency range from 0. 1 to 40GHz with a vector-network analyzer,using the short-open-loadthru （SOLT） de-embedding technique. The distributed parameters of the CPWs are extracted from the measured S-parameters.

Time-dependent Wave Packet Quantum Scattering Study of Reaction S（3p）＋H2→HS＋H on a New ab initio Potential Energy Surface 3A’

A new potential energy surface is presented for the triplet state 3At of the chemical reaction S（3P）＋H2 from a set of accurate ab initio data. The single point energies are computed using highly correlated complete active space self-consistent-field and multi-reference configuration interaction wave functions with a basis set of aug-cc-pV5Z. We have fitted the full set of energy values using many-body expansion method with an Aguado-Paniagua function. Based on the new potential energy surface, we carry out the time-dependent wave packet scattering calculations over the collision energy range of 0.8-2.2 eV. Both the centrifugalsudden approximation and Coriolis Coupling cross sections are obtained. In addition, the total reaction probabilities are calculated for the reactant H2 initially in the vibrational states v=0-3 （j=0）. It is found that initial vibrational excitation enhances the title reaction.

Scattering of Oblique Surface Waves by the Edge of Small Deformation on a Porous Ocean Bed

The scattering of oblique incident surface waves by the edge of a small cylindrical deformation on a porous bed in an ocean of finite depth, is investigated here within the framework of linearized water wave theory. Using perturbation analysis, the corresponding problem governed by modified Helmholtz equation is reduced to a boundary value problem for the first-order correction of the potential function. The first-order potential and, hence, the reflection and transmission coefficients are obtained by a method based on Green＇s integral theorem with the introduction of appropriate Green＇s function. Consideration of a patch of sinusoidal ripples shows that when the quotient of twice the component of the incident field wave number along x-direction and the ripple wave number approaches one, the theory predicts a resonant interaction between the bed and the free-surface, and the reflection coefficient becomes a multiple of the number of ripples. Again, for small angles of incidence, the reflected energy is more as compared to the other angles of incidence. It is also observed that the reflected energy is somewhat sensitive to the changes in the porosity of the ocean bed. From the derived results, the solutions for problems with impermeable ocean bed can be obtained as particular cases.

2.5D scattering of incident plane SH waves by a canyon in layered half-space

This paper presents 2.5D scattering of incident plane SH waves by a canyon in layered half-space by the indirect boundary element method (IBEM). The free field response is carried out to give the displacements and stresses on the line which forms boundary of the canyon. The fictitious uniform moving loads are applied to the same line to calculate the Green's functions for the displacements and stresses. The amplitudes of the loads are determined by the boundary conditions. The displacements due to the free field and from the fictitious uniform moving loads have to be added to obtain the whole motion. The numerical results are carried out for the cases of a canyon in homogenous and in one layer over bedrock. The results show that the 2.5D wave scattering problem is essentially different from the 2D case, and there exist distinct differences between the wave amplification by a canyon in layered half-space and that in homogeneous half-space. The reasons for the distinct difference are explored, and the effects of the thickness and stiffness of the layer on the amplification are discussed.

Scattering of Surface Waves by the Edge of a Small Undulation on a Porous Bed in an Ocean with Ice-cover

Scattering of surface waves by the edge of a small undulation on a porous bed in an ocean of finite depth, where the free surface has an ice-cover being modelled as an elastic plate of very small thickness, is investigated within the framework of linearized water wave theory. The effect of surface tension at the surface below the ice-cover is neglected. There exists only one wave number propagating at just below the ice-cover. A perturbation analysis is employed to solve the boundary value problem governed by Laplace＇s equation by a method based on Green＇s integral theorem with the introduction of appropriate Green＇s function and thereby evaluating the reflection and transmission coefficients approximately up to first order. A patch of sinusoidal ripples is considered as an example and the related coefficients are determined.

A Free Surface Frequency Domain Green Function with Viscous Dissipation and Partial Reflections from Side Walls

The free-surface Green function method is widely used in solving the radiation or diffraction problems caused by a ship or ocean structure oscillating on the waves. In the context of inviscid potential flow, hydrodynamic problems such as multi-body interaction and tank side wall effect cannot be properly dealt with based on the traditional free-surface frequency domain Green function method, in which the water viscosity is omitted and the energy dissipation effect is absent. In this paper, an open-sea Green function with viscous dissipation was presented within the theory ofvisco-potential flow. Then the tank Green function with a partial reflection from the side walls in wave tanks was formulated as a formal sum of open-sea Green functions representing the infinite images between two parallel side walls of the source in the tank. The new far-field characteristics of the tank Green function is vitally important fur improving the validity of side-wall effects evaluation, which can be used in supervising the tank model tests.

Scattering loss in optical waveguide with trapezoidal cross section

To get the scattering loss of the trapezoidal core waveguide,a new analysis model is presented based on the perturbation equivalent method and modified effective-index method.Firstly,the trapezoidal core waveguide is successfully equivalent to the rectangular one with both restricting the same optical field energy by adopting the perturbation method,Then,the equivalent rectangular core waveguide is decomposed into two slab waveguides by employing the modified effective-index method,The trapezoidal core waveguide scattering theory model is established based on the slab waveguide scattering theory.With the sidewalls surface roughness in the range from 0 to 100 nm in the single model trapezodial core waveguide,optical simulation shows excellent agreement with the results from the scattering loss model presented.The relationship between the dimension and side-wall roughness with the scattering loss can be determined in the trapezoidal core waveguide by the scattering loss model.

Waves scattering induced by an interface crack in a coated material

This paper deals with the two-dimensional problem of elastic wave scattering from a finite crack at the interface between a coated material layer and its substrate. By adopting the Fourier transform method and introducing the crack opening displacement function, the boundary value problem is simplified for numerically solving a system of Cauchy-type singular integral equations by means of Jacobi polynomial expansion. The stress intensity factors and the crack opening displacements are defined in terms of the integral equations solutions. The influence of the dimensionless wave number and the ratio of crack length to layer thickness on the stress intensity factors and crack opening displacements are discussed.

Wave steepness retrieved from scatterometer data in a genetic algorithm

Wave steepness is an important characteristic of a high sea state, and is widely applied on wave propagations at ports, ships, offshore platforms, and CO2 circulation in the ocean. Obtaining wave steepness is a difficult task that depends heavily on theoretical research on wavelength distribution and direct observations. Development of remote-sensing techniques provides new opportunities to study wave steepness. At present, two formulas are proposed to estimate wave steepness from QuikSCAT and ERS-1/2 scatterometer data. We found that wave steepness retrieving is not affected by radar band, and polarization method, and that relationship of wave steepness with radar backscattering cross section is similar to that with wind. Therefore, we adopted and modified a genetic algorithm for relating wave steepness with radar backscattering cross section. Results show that the root-mean-square error of the wave steepness retrieved is 0.005 in two cases from ERS-1/2 scatterometer data and from QuikSCAT scatterometer data.

Scattering of Plane P Waves by Circular-arc Canyon Topography:High-frequency Solution

Through the Fourier-Bessel series expansion of wave functions,the analytical solution to the two-dimensional scattering problem of incidental plane P waves by circular-arc canyon topography with different depth-to-width ratio is deduced.Unlike other existing analytical solutions,in order to ensure that the analytical solution is valid for higher frequency incident waves,the asymptotic properties of cylindrical functions are in this paper introduced to directly determine the unknown coefficients of scattering waves,avoiding the solution of linear equation systems and corresponding numerical issues,which in turn expand the frequency band in which the analytical solution is valid.Comparison with other existing analytical solutions demonstrates that the proposed analytical solution is correct.Furthermore,the scattering effects of a circular-arc canyon on the incident plane P wave are analyzed in a comparatively broad frequency band.

Three-dimensional Scattering of Obliquely Incident Plane SH Waves by an Alluvial Valley in a Layered Half-space

The indirect boundary element method （IBEM） is used to study three-dimensional scattering of obliquely incident plane SH waves by an alluvial valley embedded in a layered half-space. The free-field response of the layered half-space is calculated by the direct stiffness method, and dynamic Green＇s functions of moving distributed loads acting on inclined lines in a layered half-space are calculated to simulate the scattering wave field. The presented method yields very accurate results since the three-dimensional dynamic stiffness matrix is exact and the moving distributed loads can act directly on the valley boundary without singularity. Numerical results and analyses are performed for amplification of obliquely incident plane SH waves around an alluvial valley in a uniform half-space and in single layer over half-space. The results show that the three-dimensional responses are distinctly different from the two-dimensional responses, and the displacement amplitudes around alluvial valleys in a uniform haft-space are obviously different from those in a layered half-space.

A Note on the Solution of Water Wave Scattering Problem Involving Small Deformation on a Porous Channel-Bed

The solution of water wave scattering problem involving small deformation on a porous bed in a channel, where the upper surface is bounded above by an infinitely extent rigid horizontal surface, is studied here within the framework of linearized water wave theory. In such a situation, there exists only one mode of waves propagating on the porous surface. A simplified perturbation analysis, involving a small parameter ε （≤1） , which measures the smallness of the deformation, is employed to reduce the governing Boundary Value Problem （BVP） to a simpler BVP for the first-order correction of the potential function. The first-order potential function and, hence, the first-order reflection and transmission coefficients are obtained by the method based on Fourier transform technique as well as Green＇s integral theorem with the introduction of appropriate Green＇s function. Two special examples of bottom deformation： the exponentially damped deformation and the sinusoidal ripple bed, are considered to validate the results. For the particular example of a patch of sinusoidal ripples, the resonant interaction between the bed and the upper surface of the fluid is attained in the neighborhood of a singularity, when the ripples wavenumbers of the bottom deformation become approximately twice the components of the incident field wavenumber along the positive x -direction. Also, the main advantage of the present study is that the results for the values of reflection and transmission coefficients are found to satisfy the energy-balance relation almost accurately.

Surface Corrugation in Rotational and Diffractive Scattering of O_2 from LiF(001)

A quantum dynamic calculation on a five-dimensional O2/LiF （001） model system is performed using themulti-configuration time-dependent Hartree method.The obtained results show that the mechanism of rotational anddiffractive excitation in details: Comparison with the rotational excited state, the initially non-rotational state is seento favor the inelastic scattering in the rotational excitation process.The surface corrugation can damp the quantuminterferences and produce a greater amount of rotational inelastic scattering at the expense of the elastic process inthe rotational excitation process.The diffraction process and the average energy transferred into the rotational anddiffractive mode are also discussed.

An Alternative Method to Study Wave Scattering by Semi-infinite Inertial Surfaces

A new method to solve the boundary value problem arising in the study of scattering of two-dimensional surface water waves by a discontinuity in the surface boundary conditions is presented in this paper. The discontinuity arises due to the floating of two semi-infinite inertial surfaces of different surface densities. Applying Green＇s second identity to the potential functions and appropriate Green＇s functions, this problem is reduced to solving two coupled Fredholm integral equations with regular kernels. The solutions to these integral equations are used to determine the reflection and the transmission coefficients. The results for the reflection coefficient are presented graphically and are compared to those obtained earlier using other research methods. It is observed from the graphs that the results computed from the present analysis match exactly with the previous results.

Broadband Analytical Solution to the Scattering of Plane SV Waves by Circular Cylindrical Canyons

Based on Fourier-Bessel series expansion of wave functions,an analytical solution to 2-D scattering ofincident plane SV waves by circular cylindrical canyons with variable depthto-width ratios is deduced in this paper. Unlike other analytical solutions,this paper uses the asymptotic behavior of the cylindrical function to directly define the undetermined coefficients of scattered waves,thus,avoiding solving linear equation systems and the related numerical computation problems under high-frequency incident waves,thereby broadening the applicable frequency range of analytical solutions. Through comparison with existing analytical solutions,the correctness of this solution is demonstrated. Finally, the incident plane SV wave scattering effect under circular cylindrical canyons in wider frequency bands is explored.