Analytical solution of water table fluctuations above an inclined leaky layer due to ditch recharge

Ditch recharge is a method used for raising a water table. However, if the aquifer lies above a leaky layer, then the leaky bed will have an effect on the height of the water table. This paper attempts to provide an analytical solution of the transient state to the linearized Boussinesq equation. The solution proposed in this paper is intended for a generalized form of the leaky layer, with the boundary condition of the water level moving according to an exponential form. The results of theoretical analysis and experimental studies can provide a much better explanation of ditch recharge on an inclined leaky layer. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthetic seismograms in heterogeneous media by one-return approximation

When reverberations between heterogeneities or resonance scattering can be neglected but accumulated effects of forward scattering are strong, the Born approximation is not valid but the De Wolf approximation can be applied in such cases. In this paper, renormalized MFSB (multiple-forescattering single-backscattering) equations and the dual-domain expression for scalar, acoustic and elastic waves are derived by a unified approach. Two versions of the one-return method (using MFSB approximation) are given: One is the wide-angle dual-domain formulation (thin-slab approximation); the other is the screen approximation. In the screen approximation, which involves a small-angle approximation for the wave-medium interaction, it can be seen clearly that the forward scattered, or transmitted waves are mainly controlled by velocity perturbations; while the backscattered or reflected waves, by impedance perturbations. The validity of the method and the wide-angle capability of the dual-domain implementation are demonstrated by numerical examples. Reflection coefficients of a plane interface derived from numerical simulations by the wide-angle method match the theoretical curves well up to critical angles. For the reflections of a low-velocity slab, the agreement between theory and synthetics only starts to deteriorate for angles greater than 70°. The accuracy of the wide-angle version of the method could be further improved by optimizing the wave-number filtering for the forward propagation and shrinking the step length along the propagation direction.     

Improved version of BTOPMC model and its application in event-based hydrologic simulations

In this paper, a grid-based distributed hydrological model BTOPMC (Block-wise use of TOPMODEL) is introduced, which was developed from the original TOPMODEL. In order to broaden the model’s application to arid regions, improvement methodology is also implemented. The canopy interception and soil infiltration processes were incorporated into the original BTOPMC to model event-based runoff simulation in large arid regions. One de-signed infiltration model with application of time compression approximation method is emphasized and validated for improving model’s performance for event hydrological simulations with a case study of Lushi River basin.     

Finite volume scheme for the solution of 2D extended Boussinesq equations in the surf zone

In this paper, a hybrid finite volume-finite difference scheme is applied to study surf zone dynamics. The numerical model solves the 2DH extended Boussinesq equations proposed by Madsen and Sørensen (1992) where nonlinear and dispersive effects are both relevant whereas it solves NSWE equations where nonlinearity prevails. The shock-capturing features of the finite volume method allow an intrinsic representation of wave breaking and runup; therefore no empirical (calibration) parameters are necessary. Comparison with laboratory measurements demonstrates that the proposed model can accurately predict wave height decay and mean water level setup, for both regular and solitary wave breaking on a sloping beach. The model is also applied to reproduce two-dimensional wave transformation and breaking over a submerged circular shoal, showing good agreement with experimental data.     

跨断层监测数据奇异值的发现

在跨断层多期复测整体平差基础上分析了一期数据对最小二乘结果之影响,探讨了跨断层监测中异常数据的发现问题。     

Acoustic numerical simulation for VTI media

The generality to anisotropy of the earth media can be proved by a lot of research and observation, which is shown by the elastic parameters of the seismic wave changes with the direction of propagation. Actually, computational efficiency is very low, when simulating on the elastic anisotropie media, for the complicated and multi-parameters computation, which becomes a disadvantage to the succeeding migration and imaging pro-cedure. Using acoustic approximation in the VT[ media is an advisable simplification for the elastic wave simu-lation in that setting S-velocity into zero can greatly reduce the computational amount as well as get the same simulation effect. The authors get an acoustic approximation formula, then gain an anisotropic wave equation with 2-order in time and 4-order in space by inverse Fourier transformation, and dispel with the dispersion by adopting the high order finite difference operator in space and remove the edge reflection using the absorption attenuation boundary. Finally, the feasibility and effectiveness of this algorithm can be proved by the snaps and synthetic records.     

Geopotential Reconstruction,Decomposition, Fast Computation,and Noise Cancellation by Harmonic Wavelets

Harmonic wavelets are introduced within the framework of the Sobolev-like Hilbert space H of potentials with square-integrable restrictions to the Earth's (mean) sphere _R . Basic tool is the construction of H-product kernels in terms of an (outer harmonics) orthonormal basis in H. Scaling function and wavelet are defined by means of so-called H-product kernels. Harmonic wavelets are shown to be building blocks that decorrelate geopotential data. A pyramid scheme enables fast computations. Multiscale signal-to-noise thresholding provides suitable denoising. Multiscale modelling of the Earth's anomalous potential from EGM96-model data is illustrated by use of bandlimited harmonic wavelets, i.e. Shannon and CP-wavelets.     

基本气流的垂直切变对热带行星尺度大气波动的影响

通过一个赤道β平面上的绝热无摩擦的两层模式,讨论了线性垂直切变的纬向基本气流对热带行星尺度大气波动的影响。在长波近似下,当有纬向基本气流垂直切变时,可得到与东传Kelvin波和西传Rossby波对应的不稳定模态。对不稳定的Kelvin波模态,其相速受垂直切变的影响不大,而对不稳定的Rossby波模态,切变越大,西传速度越小。基本气流的垂直切变主要影响热带Rossby波。