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141.
142.
Rumpa Chakraborty 《地球物理与天体物理流体动力学》2013,107(5):481-496
The two-dimensional problem of the generation of water waves due to instantaneous disturbances prescribed at the bed of a beach sloping at an arbitrary angle is studied here. It is formulated in terms of an initial-boundary-value problem for the velocity potential describing the motion in the fluid region assuming the linear theory. Using the Laplace transform in time and the Mellin transform in distance, the problem is reduced to solving a difference equation whose method of solution is of considerable importance in the literature. The form of the free surface is obtained in terms of a multiple infinite integral that is evaluated by the method of steepest-descent. For some prescribed forms of the disturbance at the bed of the beach, the free surface is depicted in a number of figures for different beach angles. It is observed that as the beach angle decreases, the maximum wave height increases, which is plausible. 相似文献
143.
本文以P波和SV波波场比值,提出层状介质情况下透射波波场的反向重建算法原理,并据此给出在已知介质速度值时,求介质层厚度的反演方法。文中还以深源远震记录波形资料给出反演算例,证实本文的算法是可行的。 相似文献
144.
This study shows the usefulness of the semivariogram for modelling sand ripples created by water flows of varied flow intensity. A combination of two mathematical functions is fitted to each sample semivariogram, that is an exponential (or stochastic) component and a periodic component. The parameters of each of these components have direct physical meaning. A non-dimensional ratio combining the two parameters of the exponential model is interpreted as a regularity index (which increases with the degree of regularity of bedform arrangement). This regularity index is inversely related to the Froude number of the flow. The non-dimensional wavelength, estimated from the dominant periodic function, is also inversely and closely related to the Froude number. The wave height, accurately estimated from properties of the two fitted components, is a direct function of flow velocity and is also proportional to the standard deviation of bed elevations. The bedform shape introduces a considerable discrepancy between the generally assumed normal frequency distribution and the empirical distributions of bed height. The series of bed elevations are generally characterized by a mixture of normal distributions having the same variance but different means. The calculation of a covariance assuming a constant and single mean (as in spectral analysis) can therefore be misleading and the problem may be avoided by using the semivariogram. 相似文献
145.
大气中许多模式可化为F''=AF/F+B(AB≠0)一类非线性常微分方程。利用常微分方程定性理论说明了该方程存在非线性波解,讨论了其周期的计算问题,并求得了波解及其周期的近似表达式。 相似文献
146.
L. N. Germanovich R. L. Salganik A. V. Dyskin K. K. Lee 《Pure and Applied Geophysics》1994,143(1-3):117-149
147.
148.
给出了判断断裂之间有无相互作用的力学判据.为了研究断裂间相互作用对地球物理场的影响,对若干类常见断裂系的扩展过程及扩展过程中的声发射b 值和波速变化进行了模拟实验研究.结果表明,各种断裂系由于相互作用的不同,扩展过程,声发射b 值和波速度化均有明显的不同特征. 相似文献
149.
澜沧—耿马地震震源动力学参数研究 总被引:8,自引:5,他引:8
本文使用沧澜—耿马地震主震后在震区建立的数字地震仪记录,用波谱法测算澜沧—耿马余震的震源动力学参数。就这些参数的统计特征,对该双主震型两主震区的地下介质不同状态予以讨论。 相似文献
150.
Transmission fluctuations across an array and heterogeneities in the crust and upper mantle 总被引:1,自引:0,他引:1
Adopting the spectral approach, we derive the formulation of angular coherence and transverse coherence of transmission fluctuations. Our derivation and results provide new insight on transmission fluctuation analysis. A review of research work on fluctuation analysis using observations at large seismic arrays such as LASA and NORSAR-follows. We point out that the model of a single-layer Gaussian medium cannot explain the angular coherence of NORSAR data and a more general model of a non-Gaussian, multi-scale, vertically inhomogeneous random media is needed. The model of a two-layer power-law medium proposed by Flatté and Wu is among the simplest of such models. 相似文献