排序方式： 共有25条查询结果，搜索用时 31 毫秒
1.
三角洲内部潮汐不对称性与三角洲地貌演变方向有重要关系。目前诸多研究关注海洋、陆地边界的改变对三角洲内的潮汐不对称性演变规律的影响。实际上, 大规模的河口工程也会对三角洲内的潮汐不对称性产生影响。在众多河口工程中, 河口挡潮闸由于直接削弱口门处海洋潮动力, 影响最为直接。荷兰三角洲是潮动力主导型三角洲, 受洪潮灾害影响较为严重, 为此在荷兰西南部修建了世界上著名的三角洲挡潮闸工程。文章以荷兰莱茵河-默兹河三角洲为研究对象, 分析以挡潮闸为主的河口工程对三角洲内河网潮汐不对称性演变特征的影响。选取莱茵河-默兹河三角洲13个潮位站点的50~60年的水文资料, 利用非平稳调和分析方法计算分析三角洲内部潮汐传播特性, 并进一步研究潮汐涨落潮历时不对称性演变特征, 揭示河口挡潮闸工程对潮汐河网中潮汐动力和潮汐不对称性的影响。研究表明, 莱茵河-默兹河三角洲为显著的涨潮占优型河口, 潮汐不对称现象总体向上游沿程增强。河口挡潮闸修建后受河网径流量和潮动力剧烈变化的影响, 封闭的南部通道内的潮波大幅度削弱, 潮汐不对称现象在下游增强在上游减弱。北部、中部通道其他站点则因为通道径流增大, 潮汐不对称现象增强, 中部站点变化更为显著。 相似文献
2.
Deconvolution is an essential step for high-resolution imaging in seismic data processing. The frequency and phase of the seismic wavelet change through time during wave propagation as a consequence of seismic absorption. Therefore, wavelet estimation is the most vital step of deconvolution, which plays the main role in seismic processing and inversion. Gabor deconvolution is an effective method to eliminate attenuation effects. Since Gabor transform does not prepare the information about the phase, minimum-phase assumption is usually supposed to estimate the phase of the wavelet. This manner does not return the optimum response where the source wavelet would be dominantly a mixed phase. We used the kurtosis maximization algorithm to estimate the phase of the wavelet. First, we removed the attenuation effect in the Gabor domain and computed the amplitude spectrum of the source wavelet; then, we rotated the seismic trace with a constant phase to reach the maximum kurtosis. This procedure was repeated in moving windows to obtain the time-varying phase changes. After that, the propagating wavelet was generated to solve the inversion problem of the convolutional model. We showed that the assumption of minimum phase does not reflect a suitable response in the case of mixed-phase wavelets. Application of this algorithm on synthetic and real data shows that subtle reflectivity information could be recovered and vertical seismic resolution is significantly improved. 相似文献
3.
地球物理信号处理的进展和今后方向 总被引：3，自引：0，他引：3
本文简要叙述了近年来我国地球物理信号处理的进展和国际动态.其中包括:强干扰背景下微弱地球物理信号的提取;非稳态地震前兆信息的处理;现代谱估计的进展;瞬态谱理论在地球物理资料处理中的应用;畸变信号恢复的研究以及其它有关信号处理的研究. 相似文献
4.
5.
地震子波估计是地震资料处理和解释中的一个关键问题,子波估计的可靠性会直接影响反褶积和反演的准确度.现有的子波估计方法分为确定型和统计型两种类型,本文通过结合这两类方法,利用确定型的谱分析法和统计型的偏度最大化方法,分别提取时变子波的振幅和相位信息,得到估计的时变子波.这种方法不需要对子波进行任何时不变或相位等的假设,具有对时变相位的估计能力.进而利用估计时变子波进行非稳态反褶积,提高地震记录的保真度,为精细储层预测和描述提供高质量的剖面.理论模型试算验证了方法的可行性,通过实际地震资料的处理应用,表明该方法能有效地提取出子波时变信息. 相似文献
6.
地震发生中长期预测中的非稳态泊松模型 总被引：3，自引：0，他引：3
基于实际地震的发生在一个活动期内具有加速活动的特点 ,作者提出一种非稳态泊松模型。与稳态泊松模型中地震发生率 ν为常数相对应 ,该模型中地震发生率 ν是随时间呈指数性增加。采用对数似然方法 ,通过使其最大化来确定模型的参数。作者以一个假想的时间序列 ,讨论了非稳态与稳态泊松模型之间的差别 ,并将该模型实际应用于华北地区汾渭地震带和华北平原地震带的中长期预测中 相似文献
7.
The conventional nonstationary convolutional model assumes that the seismic signal is recorded at normal incidence. Raw shot gathers are far from this assumption because of the effects of offsets. Because of such problems, we propose a novel prestack nonstationary deconvolution approach. We introduce the radial trace （RT） transform to the nonstationary deconvolution, we estimate the nonstationary deconvolution factor with hyperbolic smoothing based on variable-step sampling （VSS） in the RT domain, and we obtain the high-resolution prestack nonstationary deconvolution data. The RT transform maps the shot record from the offset and traveltime coordinates to those of apparent velocity and traveltime. The ray paths of the traces in the RT better satisfy the assumptions of the convolutional model. The proposed method combines the advantages of stationary deconvolution and inverse Q filtering, without prior information for Q. The nonstationary deconvolution in the RT domain is more suitable than that in the space-time （XT） domain for prestack data because it is the generalized extension of normal incidence. Tests with synthetic and real data demonstrate that the proposed method is more effective in compensating for large-offset and deep data. 相似文献
8.
Seismic risk analysis and mitigation of spatially extended structures require the synthesis of spatially varying ground motions in the response history analysis of these structures. These synthetic motions are usually desired to be spatially correlated, site reflected, nonstationary, and compatible with target design response spectra. In this paper, a method is presented for simulating spatially varying ground motions considering the nonstationarity, local site effects, and compatibility of response spectra. The scheme for generating spatially varying and response spectra compatible ground motions is first established for spatial locations on the ground surface with varying site conditions. The design response spectrum is introduced as the “power” spectrum at the base rock. The site amplification approach is then derived based on the deterministic wave propagation theory, by assuming that the base rock motions consist of out-of-plane SH wave or in-plane combined P and SV waves propagating into the site with assumed incident angles, from which tri-directional spatial ground motions can be generated. The phase difference spectrum is employed to model ground motions exhibiting nonstationarity in both frequency and time domains with different site conditions. The proposed scheme is demonstrated with numerical examples. 相似文献
9.
Many natural phenomena, including geologic events and geophysical data, are fundamentally nonstationary ‐ exhibiting statistical variation that changes in space and time. Time‐frequency characterization is useful for analysing such data, seismic traces in particular. We present a novel time‐frequency decomposition, which aims at depicting the nonstationary character of seismic data. The proposed decomposition uses a Fourier basis to match the target signal using regularized least‐squares inversion. The decomposition is invertible, which makes it suitable for analysing nonstationary data. The proposed method can provide more flexible time‐frequency representation than the classical S transform. Results of applying the method to both synthetic and field data examples demonstrate that the local time‐frequency decomposition can characterize nonstationary variation of seismic data and be used in practical applications, such as seismic ground‐roll noise attenuation and multicomponent data registration. 相似文献
10.
不连续地质体（如断层）的自动检测一直以来都是叠后地震数据解释中的关键问题之一,尤其在三维情况中尤为重要.然而,大多数边缘检测和相干算法都对随机噪声很敏感,随机噪声衰减是叠后地震数据解释的另一个主要问题.针对构造保护去噪和断层检测问题,本文基于非平稳相似性系数完善一种构造导向滤波方法并且提出一种自动断层检测方法,形成了一套匹配的处理技术.该构造导向滤波既能够有效地衰减随机噪声又可以很好地保护地震资料中的断层等信息不被破坏,增强地震剖面中弯曲、倾斜同相轴的连续性.根据地震数据局部倾角走向,利用相邻道构建当前地震道的预测,通过预测道的叠加得到参考道,计算预测道与参考道之间的非平稳相似性系数可以设计出数据驱动的加权中值滤波.另一方面,预测道与原始道之间的非平稳相似性系数能够用于带有断层指示性的相干分析.这两种方法都基于构造预测和非平稳相似性系数,但是使用不同的调节参数和处理方案.理论模型和实际数据的处理结果证明了本文提出构造导向滤波和断层检测方法的有效性. 相似文献